How it Works
Minolta
Loading...
XD-11
Service Manual
56 pgs9.84 Mb1

Minolta XD-11 Service Manual

Minolta XD-11 Repair Gui de
Figure IB
OVERRANGE LED
SHUTTER-SPEED SCALE
UNDERRANGE LED
DIAPHRAGM WINDOW
Figure 3 Figure 4
ring then c omes against the minimum- aperture lever, Fig. 1. As t he tab pushes the minim um-aper ture lever from lef t to rig ht, it programs the meter ing sys tem for the smallest f/stop of the particular lens.
Only the MD series of lenses has the mi nimum-aperture tab on the diaphragm- settin g ring. Although t he earlier MC lenses will couple to the diaphragm- metering ring, they don' t have the tab whi ch position s t he minimum-aperture lever. So, if you install an MC lens on the XD-11, th e LED display won't indicate an automatically programmed f/stop. You'll only be able to turn on one LED — t he
over range LED.
You'll also get n o diaphragm readout if you fo rget to set the smallest f/stop on the MD lens. The c alib ration for the smallest f/stop has a green color code.
Since an optical sy stem reflects th e select ed calibration in to the finder, you can quickly set the d iaphragm for the "S "
mode. Simply rotat e the diaphragm- se tting ring until t he green number ap
pears in the finder, Fig. 4.
Now turn the speed knob to select the shutter speed you want. As lo ng as t he LED display indicates an f/stop in the usable diaphragm range, the camera delivers the shutter speed you've selected. It then limits how far the dia phragm can close according to your select ed s hu tte r speed and to t he light conditions.
Since the XD-11 alr eady has shutter- speed control circuitry, it can go an e xtra step to make su re you don't get an inco r
rect exposure. Perhaps the camera can't progr am the r ight f/stop for the partic ular combi natio n of light level and shutter speed. A glanc e at the LED readout tells you to s elect a different shutter speed. But, if you fail to make the necessary cor rection, the camera's "comput er" takes over — it automati cally changes the shut ter speed for you.
The camera lets you know when you're going to get a shutter speed that' s dif feren t from the one you've selected — it turns on one of the range-limits LEDS as you star t depressing the release button. If the overrange LED turns on, you’ll get an exposure tim e that's faster than the speed- kno b se tting. If the underrange LED turns on, you'll get an exposure time that's slower than the s peed-knob setting.
To program the diaphragm open ing, the XD-11 contr ols the movement of the diaphragm-closing lever, Fig. 5. The
diaphrag m-closing lever moves from ri ght to left before the mirror swings to the tak ing position. If the diaphragm-closin g lever moves its ful l d istance, it all ows the dia phragm to stop down to the smallest
f/stop. However, by l imi ting t he move
ment of the diaphragm-closing lever, the XD-11 selects other aperture sizes.
A comb ination magnet (permanent
magnet plus electromag net) limits the m ovement of the diaphragm-closing lever. As the diaphragm-closing lever sta rts to move, the permanent mag net
holds its armature. Then, when the dia phragm reaches the proper o pen ing size, the ci rcuit discharges a capacitor th rough the coil that's wound around the
pe rmanent- ma gnet c ore. The s purt of
current momentarily disables the perma
nent magnet.
Now the armature of the combina tion
magnet jumps away from the core. And the pawl-shaped end of the armature
engages the ratchet teeth of a gear whi ch
rotates as the dia phragm-c losing lever
moves. Stopping the r otation of the gear
also stops the movement of the
diaphrag m-closing lever.
In tu rn, the dia phr agm-closing lever
sto ps the spring-loa ded diaphragm from
closing any f urther. At t he other settings
of the mode selector, the capacitor nev er
disc harg es through the coil of th e com
bination magnet. As a result, the
diaphrag m-closing lever always moves its full distance. And the diaphragm stops down to the f/stop you 've selected on the diaphragm-setting ring.
The third setting o f the mode selector
— the "M " sett ing, Fig. 2 — provides ma nually calibrated shutter speeds. Wi th the m ode selector at "M ," the shutter alw ays deliv ers the selected shutt er speed. The LED display now serves as a
cross-c oupl ed mete r; it tells you w hat shut ter speed wil l provide proper ex
posure according to the light conditions
and to the diaphr agm setting . A lso, as
you turn the mode sele ctor from the "A "
position to the "M " po sitio n, the
viewfinder mask uncovers t he shutter-
speed calib ration in the finder, Fig. 4.
Although the speeds are manually select ed at the "M " mode, t hey're still ele ctronically controlle d. Co nseq uently, all th ree functions dep end on battery
power . In fact, even the s hu tte r release requires battery power. A second com bination magnet in the XD-11 releases the mirror when you push t he release button far enough to close the release switc h.
The XD-11 uses two S-76 silver-ox ide batteries housed at the bott om of the camera. What if the batte ries die? Yo u'll then find that the shutter won't release.
But t he XD-11 does pr ovide two
mechanical settings — "B " and " 0 ," Fig.
2. At the "B " sett ing, the shutter delivers
a mechanically contro lled bulb action. A mechanica l system then releases the mir ror. At the " 0 " setting, the shutter mechanica lly delivers the f astest full- aperture shutter speed — 1/10 0 second. So, if the batteries die, you can turn the speed knob to "0" and contin ue using the camera with electronic flash.
The electron ically con trol led "X" set
ting also provides the fla sh speed of
1/100 second. However, the " X " sett ing does depend on battery power — both for the electromagnetic release and fo r
Figure 5
Figure 6 Front-plate/mirror-cage/shutter assembly
the electronically timed exposure. You
can't use t he " X " sett ing, the "B " set
ting, or the " 0 " setting for au tomatic e x posure control. To help p revent a possible operator error, the LED display refuses to indicate a shutter-speed or diaphragm calibration at the "X ," "B ," or " 0 ” set tings, Rather, the overrange LED always turns on.
OTHER FEATURES OF THE XD-11
The XD-11 and its spinoff, the XD-5, both use the Seiko MFC modular focal- plane shu tter. With a modular focal-plane shutter, you might expect the XD-11 to have a mo dular design. It does. But the XD-11 is even more modular than most cameras using similar sh utters. You can remove the front plate, mirror cage, shutter, and flex circuit as one unit. Reaching the shutter takes a minimum amoun t of time.
Practica lly all of the electroni c com ponents mount to the flex circu it. In many cameras, the flex cir cuit causes repair problems; y ou must delicately li ft aside portion s of the flex circuit to disassemble the camera. Howeve r, the XD-11 elimi nates such problem s. Since the flex cir cuit c ome s off with the front assem bly, Fig. 6, there's little c hance of da mage.
As is typical, the flex circuit covers the penta prism. Fortunately, you don't have to lift aside the flex circuit to clean the f ocus ing screen. For that ma tter, you don't even
have t o remove the top cover. To remove the f ocusin g screen, take out the two screws that hold th e plate at the top o f the
mirror cage, Fig. 5. Lift out the cover plate and th e focusi ng-sc reen retainer. You can
now drop out the focusing screen from in side the mirror cage, Fig. 7.
Most of the remaining featu res are pretty typical of modern SLRs. Notice that the fil m-speed dial allows you to set
intent ional o verexposures or underex posures, Fig. 2. When you select the fi lm speed, the film-speed dial rotate s a brush
along the fil m-speed re sistor. Movin g the compensation lever fo r intentio nal over- exposures or underexposures rotates the enti re fil m-speed resistor with out moving the brush.
The XD-11 also accepts a p owe r winde r, the Aut o Wi nder A, and th e Minolta series of dedicate d flash unit s. The 132X, 200X, and 320X dedicated flash units automa tic ally progra m the camera for the flash speed of 1/100 second. When the flash unit charges, the ov errange LED flashes on and off in t he fin der.
CIRCUIT A T THE BOTTO M OF TH E XD-11
The batt ery-compartment cover screws into the bottom plate. So, once you remove the bottom plate, you can't power the camera with its own batteries. However, you can con nect a 3V DC power supply to the batt ery com partment, Fig. 8. Conn ect the positiv e pow er-supply lead to the batt ery- compar tme nt termina l and connect the negative power- supply lead to ground (any metal part on the camera). All the test v oltages we'll be giving are positiv e wit h respect to ground.
As you cock and release the shutte r, no tice the ac tions of the two levers at tached t o the t ransport cam — the mirror- cocking lever and the shutter-cocking lever, Fig. 9. T he clockwise rotation of the t ransport cam drives t he mirror-
cocking lever left to right in Fig. 9. T he end of the mi rro r-cocking lever then comes against the roller on the mirror- tensioning lever to charge the mirror. At the same time , the tran sport cam draws the shutter- cocking lever from left to right to charge the Seiko shutt er.
The transport l atch , Fig. 9, now drops into engagement with a notch in th e transport cam. Consequently, you can't advance the wind lever a se cond time. A fter the exposure , the mirror-ten sioning
lever swings f rom right to left, Fig. 9, and strikes the transport-releas e lever. As the transport-release lever rotates in a clock wise directio n, it dis engages the
transport latch fro m the tra nspo rt cam.
A spring attached t o the transpo rt latch and the transport-release lever provides the swi tching contact for the power
winder. With the shutte r released, the
power-winder switching contact moves into the power -winder locating bushing. Fig. 9. The locating bushing receives a pin on the power wind er. So, with the power winder attache d to the camera, the power-winder switchi ng contact touches the pin.
The po wer-winder switching co ntact now connec ts the p ower -winder pin to ground. As a result, the powe r winder goes into action; it advances the film and coc ks the shutter by rotating the pow er- wind er coupler, Fig. 9. When the shutter reaches the cocked position , the trans port latch drop s into the notch in the transp ort cam. The transport latch no w drives the power-winde r switching con ta ct away from the power-winder pin. Since t he power- winder pin no longer connects to g round, the power winder
sto ps runn ing.
At the other en d of the camera, you can see th e circuit board which contains
the mirror-re lease and diaphragm -co ntrol
component s. Fig. 8. Locate the two cap a citors — C5 and C6. These are the capa-
Figure 8
POS IT IV E BATTERY
LOC AT IN G BUS H IN G
POW E R -W IN D E R SW IT C H IN G CON T A CT
POW E R -W IN D E R COU P L ER
TR A N S P O R T CA M
Figure 9 Shutter Cocked
MIR R O R -C O C K IN G LEVER
LOOS E DU ST SEAL
IR A N S P O R T - RELEA SE LEVER
SHU TT E R C O C KI N G LEVER
citors that discharge through the coils of the comb ination magnets. C6 discharges through the coil of the mirror-release co mbin ation mag net M1; C5 discharges th ro ugh t he coil of the diaphragm-control co mbin ation magnet M2.
As yet, you can't reach th e combina tion magnets. So , if there's a prob lem in either the mirror-release circu it or in the diaphragm-con trol circuit, you m ay have to remove the front-plate as sembly. However, you can troubleshoot both cir cuits and pinpoin t the malfunction with
out further disassembly. And, if you find
th at the problem is on the circuit board,
Fig. 8, you can ma ke the repa ir without
disassembling the camera any further.
The two combina tion magnets have very similar circu its. Fig. 10 shows the cir cuit for th e mirror-release magnet M1. Transistor T6 serves as a swit ch between
the mirror-release ca pacitor C6 and the coil of the mirror-release magn et M1 . Turning on T6 a llows the capacitor to discharge through the coil. The spu rt of current
causes the armature of M1 to jump a way
from the c ore and release th e mir ror.
You can see the M1 armature in Fig. 11. Also locate the mirror-release lever in the same ill ustration. When you push the release button, you should see the end of the M1 a rmature move toward the front of the camera and strik e the mirror-release
lever.
Transistor T6 gets the release signal from the compara tor, Fig. 10. When the release switch closes, the contro l circuit sends a signal to the compar ator. T he compar ator then sw itches from a h igh state to a low state. The low volta ge ap
plied to the base of T6 turns on the tran sistor. T6 now allows the capacitor to
discharge through the coil of M1.
But notice in Fig. 10 tha t switch S1 must be closed before the compar ato r output connec ts t o the base of T6. S1 sits at the bottom of the camera, Fig. 11. When you cock the shu tter, S1 closes to connect the comparator to T6. S1 opens after th e exposure.
You can also see the part that a ctuates S1 in Fig. 11 — the nylon lug on the transport-releas e lever. As the transport- release lever swings in a clockwise direc tion, it allows S1 to close. Then, when the mirror-tensioning lever drives the transport-r elease lever in a counter clockwise d irection, the nylon lug pushes the long blade of S1 away from the short
blade.
S1 serves as a reset swit ch for th e cir cu it. But, if S1 fails t o close or makes poor electrical con tact, you'll only note
Figure 10
Figure 11
one malfunction in the camera — the shutter won' t release. With S1 open, transist or T6 ne ver gets the lo w-voltage signal from the com parator.
You can check S1 with a voltmeter. At the long blade of S1, Fig. 12, you should measure 0V with the shutter in the released position. You should measure around 2.5V at the short blade, regardless of wh ether the shutter is cocked or released. Since S1 should close when you cock the shutter, you should also measure around 2.5V at the long blade. What if you measure 0V at the long blade wit h the shutter cocked? Ap parently, S1 isn't closing.
If you have to reform the blades of SI, check the timing. Cock the shut ter and hold the win d lever fully advanced. Then,
while measuring the voltage at the long
blade of S1, allow the wind lever to return slowly to its rest position. S1 should re main op en as the transport latch drops into the first step in the tr ansport cam, Fig. 9. But S1 should close w hen the tra nsp ort latch drops into the seco nd tran sport -cam notch. So, as soon as the transpo rt latch
drop s into engagement with the second
notch, you should measure a round 2.5V at
the long blade of S1. If the timing isn't cor rect, reform the S1 blades.
TROUBLESHOOTING THE
ELECTROMAGNETIC RELEASE
SYSTEM
If the shutter fa ils to release elec- tromagnetically, you might first suspect swit ch S1 . B ut you can also check the other possibilities after remov ing the bot tom plate. The mirror-release magn et M1 may have an open coil, the mirror-relea se capacitor C6 may be op en or short ed, tra nsi stor T 6 may be open, or T6 may n ot be gettin g the release signal from the comparator .
It's also possible that the problem is mechanical rather t han electronic. To check the mechanic al release acti on, cock the shutter and push the M1 armature.
Fig. 11, toward the front of the camera. The mi rror should release. If it does, you know t he mecha nical release is working
properly. And the problem must be with
Figure 13
the circuit.
Fig. 13 shows the appr oximate voltages you should measure acro ss th e M1 com ponents. Notic e that the mirror-release capacitor C6 charges t o the full battery volt age. You should measure the +3V at the pos itive terminal of C6 regardless of whether the shutter is cocked or released.
However, before measuring voltages, you might try a quick shortin g te st to simultan eously check both capaci tor C6 and the coil of magnet M1. Cock the shutter. T hen bypass transistor T6 by shorti ng betwe en its emitter and collec tor, Fig. 13. The mirror should release.
If your shorting test releases the mirror, you know that both th e c ombination ma gnet M1 and the m irror-rele ase capa citor C6 are good. You migh t nex t t ry checking for the release signal at the base of tr ansistor T6, Fig. 13. Without de
BLA CK (GROU ND)
RED TO
* BATTERY
pressing th e release button, you should measure around 2.5V — the output of the co mparator in the "high" state . I f you measure the full 3V sign al, T6 a pparently
has a b ase-to-emit ter short. Now depress the release button. T he signal should drop to around 1.3V.
If the circuit fails to supply the release signal to the base of T6, you'll have to go further in the d isassembly. There may be a problem with the release swit ch or with the release cir cuit. But if the t ransistor T6
is a t fa ult, you won't have to go an y fur the r. You can make a fin al check on T6 by shorting between the base and the collec tor, Fig. 13. Your short connects the base to ground through the coil of M1. If the tra nsistor is good, the mirror s hould
release.
Replacing the tr ansist or gives you a
choice in repair procedure. Minolt a does supply the individu al components. But you may prefer to replace the com plete circuit board (circuit base plate B).
Now let's say that the shutter doesn't release whe n you short betwe en the emit ter and collector of T6. Either the com binati on magnet M1 or capacitor C6 could be at fault. But you might first suspect the coil of M1. The red wire co nnected to the collector of T6 goes to one si de of the coil; the other side of the coil connects to ground through a black wire, Fig. 13. To check the coil, m easure the resis tance bet ween the red coil wi re and groun d. You should measure a very low resistanc e
— arou nd 15 oh ms. I f you measure no con tinuity, you know that the combina tion magnet M1 has an open coil. You'll then ha ve to rem ove the front -plat e asse mbly to replace the combination
magnet.
Figure 14
CHE CKING THE DIAPHRAGM- CONTROL CIRCUIT
You can fol low practically the same troubleshooting procedure to check the circuit f or th e sec ond combination magnet — the diaphragm-control magnet M2. Remember, the diaphrag m-control magnet arrests the diaphragm closure in the "S " mode. If the re's a problem in the M2 control circuit, the diaphragm always stops down its fu ll amount.
In Fig. 14, note the similarit y between the diaphra gm-control circuit and the mirror-release circuit. When th e dia phr agm reaches the proper f/stop, the aperture-control co mparator switches on transistor T13. T13 then supplies th e base current which turns on t ransistor T5. Turning on T5 allow s th e diaphragm- cont rol capacitor C5 to discharge through the coil of the diaphragm -co ntrol magnet M2. M2 now repels its armature to arrest the diaphragm-closing lever.
Figure 15
Figure 16
Figure 17
BL ACK PURPLE
WHITE TO S7
VIOL ET
BROWN TO M2
BLUE
The components for th e diaphragm-
control circuit also mount to the circuit
board a t the bottom of the camera, Fig. 15. But you can't as yet see switch S7. Switch S7 is part of the mirror-release-magnet assembly M1. As th e armature of M1 jumps away from the core to release the mirror, it opens S7. Not ice in Fig. 14 that S7 mu st be open in order for transistor T13 to conduct.
In effect, ope ning S7 turns on the diaphragm-con trol circuit. At the same time, S7 provides power for th e shutter elect romagnet (the electromagnet th at
holds open the closi ng blade for the length of th e exp osure). Opening S7 also switches off the LED display.
A problem with S7, then, could cause
quite a few problem s. Althou gh you can't as yet reach S7, you ca n check i ts opera tion. Lo cate t he white wire attached to the lower circuit board, Fig. 15. Measure the voltage bet ween th e white wire and ground; you should measure 0 volt, in dicating that S7 is closed.
With S7 o pen, you should measure
aro und 1.3V at the white wire. But how
can you op en S7 to measure the voltage? One way is to hold open t he s hutter at the bulb setting. Then push the M1 ar mature. Fig. 16, away from the M1 core (toward the front of the camera). The M1 ar ma ture now opens switch S7. Conse quen tly, you should measure around 1,3V at the white-wir e connec tion, Fig. 15.
Th e technique f or holding open switch S7 also allow s you to conv eniently che ck the c oil of M2 and ca pacitor C5, Fig. 14. Con side r that the diaphragm-control cir cuit fails t o latch the diaphragm-cl osing lever; the d iaphra gm-closing lever a lways moves its full distanc e in the "S " mode. You might first check for the charge across the diaphra gm-control capacitor C5. Me asure the volt age between gro und and the pos itive C5 lead. Fig. 15; you should mea sure -t-3V.
If you're gett ing the full battery voltage across C5; th e problem could be with T5, T13, or the coil of M2. Another possibilit y is that T13 is n't getting the turn-on signal from the aperture-cont rol comparator. But you can quickly check the trans istor s and the M2 coil with shorting tests.
There are a couple of ways you can check to see if M2 repels its arm ature when C5 discharges. Try setting the mode selector to the " S " position. Then watch the diaphragm-closing lever, Fig. 5, as you
release the shutter. If there's a problem in the diaphragm-cont rol circuit , the diaphragm-closing lever always travels its full str oke.
Now short betwee n the emitter and collect or of transistor T5, Fig. 15, as you release the shutter. The diaphragm- closing lever should stop after t ravelin g a
short distance. If it doe sn' t, you know that the diaphragm-control magnet M2 and the diaphr ag m- control capacitor C5 are both doin g their jo bs.
But you may fin d that it's easier to check the opera tion if you can actually see the ar mature of M2. Just pull aside the battery compartme nt by removing its two screws, Fig. 16. You can now see the M2 assembly through a clearance cu tout in the bottom of the body casting, Fig. 17.
To check M2, hold open t he shutter at the bulb setting and disengage the M1 ar mature as previously described. Re member, pu shing the M1 armature away
from its core opens sw itch S7. S7 must be
open in order for transistor T13, Fig. 14, to turn on.
Now sh ort between the collector and the emitter of T5, Fig. 15. Y ou sh ould see the armature j ump toward the f ront of the camera. If the armatur e jumps away fro m the co re, bo th M2 and C5 must be good.
You might then suspect transistors T5 and T13, Fig. 14. While still holdin g open the shutt er on bulb w ith S7 open, try shorting betw een ground and the collec tor of T13, Fig. 15. Once again you should see the M2 armature jum p away from its core. But, if the arma ture fails to move, trans istor T5 must be defective.
If the armature does move, the pro blem may be with T13 or with the signal from the apert ure-control comparator. You can make one more shor ting test to check T13. Again hold o pen the shutter on bulb and open S7. Then short between the base of T13 and gro und. If the armature jumps away from the core, th ere's no pro blem with T13. The problem must be in the aperture-control circuit. You'll have to remove the to p cover to reach the IC that provides the turn-on signal.
Let's now consid er the other p ossibility
— the M2 a rmature does not release
when you short across transistor T5. You
might first suspect an op en coil. T o check
the coil continuity, measure the resis
tance between th e brown wire, Fig. 15,
and ground. You should measure the
resistance of the coil — around 15 ohms.
Also suspect the diaphr agm-c ont rol
ma gnet M 2 i f the di aphragm fails to stop dow n. Such a malfu nction could indi cate
a problem eithe r with the diaphragm-
control magnet or with the circuit. B ut it's usually fairly easy to pinpoint the probl em area — just check th e operatio n at the d if ferent modes. If the diaphragm fails to stop down a t all three modes — A, M, and S — suspect the dia phragm- control magnet M2. Howe ver, if the p roblem only occurs at the S mode, suspect the c ircuit.
When the diaphragm fails to stop
down, the diaphragm-control magn et
isn’t holding its armature. The armatu re
then immediately arrests the the
dia phragm-c losing lever. If the problem occurs at all three modes, try cleani ng the contact surfaces o f the arm ature and of the permanent magne t, Fig. 17. Dirt can prevent t he core from magnet ically hold ing the armature.
If cleaning doesn't do the job, the pe r manent magnet may be defe ctive. Try pushin g the armat ure of M2 awa y from
the core. Fig. 17; you should be able to feel the magnetic attraction. A defe ctive
per manent magnet requ ires that you replace M2, a job which means pulling the
fron t-plate/mirror-cage a ssembly.
Now consider the othe r po ssibility — the problem only occurs at the S mode. The symptom indicates that the diaphragm- control circuit gets the release signal as
soon as switch S7 opens. You can spo t the
problem by using the technique we describ ed earlier at the bulb setting. Watch the ar mature of M2 as you push the M1 armature
toward the front of the camera, Fig. 16. If the M2 armature now jumps away from the core, the circu it is sending the release signal right away.
To verify the m alfun ction, you might try operating the camera at the S mode while you're shorting across the base and emit ter of transis tor T13 , Fig. 15. You r short should keep transistor T13 shut off. And, as a result, the armature of M 2 should remain against the core. If the ar mature still jumps away from its core, the problem is on the cir cuit board at the bot tom of t he camera — most likely, a shorted transistor. But if the armature re mains against the core, the p roblem is in the circuit that sends the signal to T13. You m ust then remov e the fr ont-plate/ mirror- cage assembly. The p roblem cou ld be as simple as t he violet wire's shorting to ground; or a switch or IC may be defectiv e.
SUMMARY OF TROUBLESHOOTING AT BOTT OM OF CAMERA
As you can see, it's possible t o check most of the electromagnetic diaphra gm- closing and release systems from the bottom of the ca mera. What if the possi bilities we've discus sed don't get you to the problem? You'll th en have to go fur ther. For example, if the mirror won't release electromagnetically, the problem could be in the release swi tch. Yo u can check the remaining switches just by removing the to p cove r. The followin g char t summarizes the troubleshooting cove red so far.
SYMPTOM
Shutter won' t release, LEDs do not operate
Shutter won't release, LEDs operate
Diaphragm fails t o stop down, LEDs operate
All modes
S mode only
Dia phragm always stops down fu lly, "over" LED remains on
POSSIBLE CAUSE
No battery power to lower circuit bo ard
— check for 3V at red wire, Fig. 13. No
voltage — check battery c ompart.
Release swit ch (remove top cover to check)
Coil M1 open Capaci tor C6
Transistor T6
Switch SI, p oor contact Solder connections to lower c ircuit
board (red, black, yellow) No release signal from comparator
Combination magnet M2, arm ature dirty or permanent magnet defe ctive
Vi olet wire shorted to ground Transistor T13
Compara tor always presents release
signal to T13
Solder connections to lower circuit board (purpl e, whit e brown, black)
Film-speed resis tor open (remove top
cov er to check)
IC1 - DIAPH RA GM
CONTROL
PHOTOCELL
AMPLIFIER
SPEED
CONTROL
DI A PH RAGM CONTR OL
IC2 - SHUTTER-
DRIVER
RE LEAS E LOCK
FOR LED s
OU TPUT
LIGHT LEVEL + FI LM SPEED
Figure 18 Actual schematic
Figure 19
ACTUAL CIRCUIT FOR THE COMBINATION MAGNETS
Fig. 18 shows th e actual circuit for the co mbin ation magnets M1 and M2. The two IC's which drive the swit ching tran sistors mount to the flex circuit ins ide the camera. No tice in Fig. 18 that a com parator output of IC1 controls the poten tial on the emitter of T13; sw itch S7 con nects to th e T13 base (in the partial
schem atic s used earlier for ex planatio n, we show ed the comp arator cont rollin g the base of T13).
With S7 closed, the base of T13 con nects to ground. Opening S7 th en con nects the base of T13 to a po sitiv e voltage
— around 1.3V, measured at the w hite wire, Fig. 18. T13 no w has the voltag e it needs at the base. However, the tran sistor can't turn on until the emitter voltage goes less pos itive than t he base volt age.
The c om par ato r inside IC1, Fig. 18,
decides when it's time to turn on T13. IC1
actually makes its ex posure calcula tion as
the diaphra gm sto ps down. At the "S "
mode, IC1 compares the selected shutter- speed set ting at one inpu t with the light level and the film-speed setting at the other input. To stop the diaphragm at the proper f/stop, the comparator inside IC1 switche s low. The emitter of T13 now goes less positive th an the base. As a resul t, T13 turns on and allows C5 to discharge through the coil of M2.
Yo u can see h ow the comparator
makes its f/st op calculatio n in Fig. 19.
The sh utter-speed setti ng provides the in
put voltag e to one input of the com parator; the combina tion of the film-
speed setting and the photocell out put provides the volt age at the ot her input. If in put #1 in Fig. 19 is less positive than in put #2, the c om parator output remain s high to keep T13 turned off.
However, as the diaphragm stops dow n, the output of the photocell decreases. The voltage at input #2 then goes less positive. When the two inpu ts see the same voltage, the comparator knows that the diaphragm has reached the proper f/stop. N ow the comparator switches states — its out put swit ches low
and turns on T13.
Earlier, we mentio ned that S7 must open before T13 can conduct. If S7 re main s closed, the base of T13 stays at
ground potential. Remember, S7 opens when th e mirror -release combinatio n
magnet M1 repels its arma ture. Opening
S7 both applies the base bias to T13 and
disconn ects IC2 from grou nd.
IC2 serves as the driver for the LEDs. So, when S7 breaks the IC2 g round con ne ction, th e viewfinder LEDs turn off . Also, IC2 p rovides the shutter-r elease loc k for the mirr or-release combination magnet M1, Fig. 18. If the batter y vo ltage drops too low, the compara tor inside IC2
won't swit ch on transistor T6. As a result,
the mirror-release combination magnet can't release the mirror.
VARIATIONS IN THE LOWER CIRCUIT BOARD
As mentio ned pre viously, the lower cir cuit board. Fig. 20, comes as a complete unit. Alt hough w e des cribe d techniques for checking the individual compon ent s, you ca n test the complete cir cuits with one shot — just sho rt th e bases of the control transistors to ground.
Check the diaphragm-co ntrol c ircuit by
holding open the shu tter on bulb. Then
push the armature away from the core of
M1, Fig. 20, to open S7 Now short the base
of T13 (the violet or purple wire, Fig. 201 to
the camera body. You should see the ar
mature of M2 jump away from the core.
If shorting th e violet wire to gr ound
causes M2 to repel its armature, all of the
diaph ragm-control circ uit on the bottom of the camera must be worki ng. What if M2 doe sn't repel its arma ture in n ormal operation? Apparently the comparator in side IC1 isn’t switching low to provid e the emitte r bias for T13.
Similarly, you should be able to make
the mirror-release magnet M 1 repel its ar mature by shorting the yellow wire to ground (the yellow wire that c onnects to
the base of T6, Fig. 20). Shorting the yellow wire to groun d should turn on T6. If M1 repels its armature and releases the
mirror, the mirror-r elease co mp onents must be good.
If you find that there's a problem on the lower circui t board, however, you may run into a parts snag — there are two dif
fere nt versions of the board, and th e two typ es won't alway s interchange. Fig. 21 shows the early version of th e board; Fig. 22 shows the modified version.
Whether or not you can install the later
version in an earlier camera depends on the flex circuit. You must then identify the flex circuit. Alte rnately, you may have to replace the compl ete flex circuit and the l ower cir cuit board as a unit. You'll be able to ident ify the flex circuit after you remove the top cover.
REMOV ING THE TOP COVER
Unscr ew the wind- lever retaining
screw. Then disconnect the end of the wind-lever return spring, Fig. 23, as you
lift off the wind lever. Also uns crew the top-cove r retaining ring around the wind shaft. Fig. 24.
Next unscr ew t he re taining ring that
holds the speed knob. Fig. 24. Although
we us ed the bulb setting as a reference in
Fig. 24, the actual shutt er-spee d and film- speed setting s aren't important for disassembly. Remove the speed knob and not e the loose release pin. The release pin closes the switches for the met ering and release functions.
You ca n completely remove the camera back by depressing the hing e pin. Then unscr ew the rewind knob. Remove the film-speed dial b y unscrewing its retaining ring and take out the parts indicate d in
Fig. 25 — the d etent plate, the black plastic decora tor ring, the brass bushing, and the expos ure-compensat ion lever.
Finally, remove the top-cover screws. Two of the top-cover screws also hold the diaph ragm -window plate, Fig. 26. If you wish, you can remove the front decorator
plate. Fig. 26, after you take off the diaphragm-w indow plate. However, unless you know you're going t o remove the fron t- plate /mirror-cage assembly, you can leave the front decorator plate installed.
Before lifting of f the t op cover, push down the eyepiece-blind lever, Fig. 27. The eyepiece bli nd then covers the eyelens. This precaution prevents the other end of the eyepiece-blind lever f rom catching the flex circuit as you lift off t he top cover.
Figure 21 Early style board
Figure 22 Modified board
B LACK PURPLE OR VIOLE T
REPLACING THE TOP COVER
When you replace the top cover, the mo de selec tor, Fig. 24, must key to the mo de switch, Fig. 28. Fig. 28 shows the mo de switch set for manual shutter
speeds — the "M " position. To set autom atic shutter spee ds, move the
mo de switch t o the center p osit ion; move the mod e switch all the way in a counterclockw ise direction to set automatic d iaphragm openings.
Normally, you'll fin d that the mode selecto r keys most easily at the "S" set tin g. Set the mode selector in the top cov er t o "S ." Then turn the mode switch. Fig. 28, all the way in a count erclockwise dir ection. After seating the to p cover, check t o see that the viewfinder scale switche s from the diaphragm calibrations to the shutter-speed calibrations when you m ove the mode selector to "A .”
Also, with the top cover remov ed, the film-a dvance indic ator, Fig. 28, ten ds to sneak under the counter dial. Tightening the retaining ring around the wind shaft.
Fig. 24, then binds both the counter dial
and the film-adva nce indicator.
The film-advance indicator only moves when there's film in the camera. As the
film winds onto the take-up spool, it pushes forward a lever inside the take-up cha mber. The lever then moves the fil m- advance in dicator from left to right in Fig.
28. You can see the film -advance in dicator throu gh the window at the back of the top cover.
Check the film-advance ind icat or after you replace the retaining ring around the wi nd shaft. Fig. 24. Reach t o the front of the take-up spool and push forward the lever that extends i nto the take-up chambe r; the film- ad vance indicator
should mo ve in to the window. If the film- advance indicato r doesn't move, loosen
the retain ing ring. Fig. 24. Then hold for ward th e lever inside the take-up chamber so that you can see th e film-ad vance in dicator within its w indow. Continue hol ding the lever as you tighten the re
taining ring.
To replace the wind lever, first hook its
hole to the end o f the wind- lever ret urn
spri ng. Then rotat e the wind lever in a
co unterclo ckwise direction as yo u seat it over the wind shaft. The upper coil of the
SP E E D K N O B RE T A IN I N G R I NG
wind lever re turn spring sometimes
sneaks under the wind lever. If tha t hap pens, the wind lever won't return freely
after you replace t he cover screw.
The film-speed dial can also be tric ky to install. Replace the exposure-co mpensation lever and the deten t rack as shown in Fig. 29; notice that the slot in the exposure- compen sation lever fits over the tab on the film-speed resistor ring. Then replace the black plastic d ecorator ring. Fig. 25. The notch in the decorator ring goes under the exposure-compensation lever.
TO P C O V E R RE T AI N IN G R IN G
EX P O S U R E C O M P E N S A T I O N LEVER /
DE C O R A T O R RIN G
EYE P IE C E- BL I ND L EVER
DET E NT PLATE
UP P E R BR A S S BU S H I N G
Figure 24
FRO NT - DE C O R A T O R PLA TE v
Figure 26
MO D E S E L EC T O R
LON G T O P - C O V E R SC R E W S I
mmo
Figure
TO P -C O V E R SC R E W
-----
MO D E S W I T C H IN M M O D E
A M O D E
Figure 29
TAB ON RESIS TOR RING
SPRING ON EXPOSUR E-CO MPENSATION LEVER
Ne xt seat th e upper brass bushing. Fig.
25. Two tabs on the underside of the up per bra ss bushin g fit into the two slots of the lower brass bushing. Fig. 29. Also,
the ends of the spring attached to the expos ure -comp ens ation lever, Fig. 29, must come against t he outer cir cum
ference of the upper brass bushing.
Finally, seat the film -speed dial wi th its
slot over the tab on the film-speed brush.
Fig. 30. Replace the b lack pla te (the plate with the compensation calibrations) so that the film-speed window is over the film-speed cali brat ions. Then rota te the
black pla te u nti l you feel its tab drop into
one of t he slot s in the upper brass
bushing .
CHECKING THE FILM-SPEED
RESISTOR
With the top cover removed, you can
see the parts of the film-speed resistor.
Fig. 31. If you know you're going to remove the front-plate/m irr o r-cage assembly, lift out the f ilm-speed lock, the lower brass bush ing, and the film-speed brush. How ever, if you're trouble shootin g or adjusting the camera, reassemble the film-speed dial.
Why? With the film-speed dial remov ed, the film-speed brush doesn' t make firm contact with the resistor rin g, Fig.
31. T he camera then exhibits the symp toms of an open film-speed resistor:
Figure 31
- only the overrange LED turns on
- the diaphragm always stop s down fully in the S mode
-th e shutter de livers only th e
mechanical speed ( 1/1000 second) in either automatic mode.
Even wit h the film -speed dial reas sembled, there's a trick to setting t he film speed. With the top cover removed,
neithe r t he film-speed lock no r the exposure-compensation lever keys t o anything. You must s et both part s in their
pro per positions before th e film-speed
setting is valid.
A detent spring on t he bottom of the resistor ri ng prov ides the click stops for the compensation settings. The detent spring catches one of five detent slots in the rewind-shaft suppor t plate. Fig. 31. First turn the exposure-compensa tion lever until the deten t spring seats in the center slot; that's the "no rmal" position. The two slots on each side of the "no rmal" position provide the intentional overexposure and undere xposure setting s.
Next rotate the film-sp eed lock to align the "0" com pensation calibra tion with the index on the compensa tion lever. As lon g as the "0 " calibration remains a lign-
ed, you can believe the film-speed set
ting. Naturally, Minolta has a spe cial top cover whic h holds the film-spe ed dial in position for test s and adju stmen ts (ASA
100, 0 co mpensation). But, without the special top cover, you'll have to make sure the parts don't shift out of position.
Fig. 32 illustrates the ope ration o f the film-spe ed resistor. Se tting the film speed moves t he film-speed brush along the resistance band; chan ging the com pensa tio n setting ro tates the resistor ring. In
either case, you're changing the resis
tance be tween th e blue wire and t he gray
wi re to program the operational amplifier
inside IC1.
If you measure the resistance between
the purpl e wire and th e gray wire, Fig. 32, you should read the value of the entire
resistance b and — arou nd 28K. Betwe en
the b lue wir e and the gray wire, you should see the resistance smoothly decrease as you set slower film speeds; the resistanc e sh ould g o from arou nd 28K to around 847 ohms . Here are the re sistance values measured from a repre sentat ive camera for differen t compe nsa tion settings at ASA 100:
tact at the left-hand side of the brush.
Fig. 33, causes the overrange LED to re main on. Also, the shutter delivers only its mech anical speed. Poor contact at the right-ha nd side causes the shutter to hang open at all modes.
Later models of the camera have a sup port arm above the mode switch; the sup port arm maintains firm brush contact .
FILM-SPEED BR USH
^V W V W W V A
Figure 32
But, in earlier models, the mode switch should be on e of your first suspects . You can pinpoin t a problem to the mode switch by using volt age tests . However, you m ight first repla ce the speed knob and the win d lever. You’ll the n be able to
troubleshoot most of the electronics in
the camera — even though you can't as yet reach all of the actua l components.
PURPLE
BLUE
GRAY
+ 1
0
-1
5.84K
9.06K
12.55K
CHE CKING THE MODE SWITCH
Bef ore replacing the speed knob, you
might take a look at th e speed selector and the mode switc h at the win d-lever end of the camera. Fig. 33. At the "A ” se tting, the nut on the mo de s witch
comes against the mask lever. The nut
then pushes the mask lever in a clockwise direc tion. In tu rn, the mask lever pulls the
mask over the windo w for the shutter- speed indication. Remember, the shutter- speed s etting has no meaning in the "A" mode.
The spring-lo aded scale to the front of the pentaprism provides the shutter- speed indic ation. Fig. 34. A tun gsten wire couples the shut ter-speed scale to the speed selector. T urnin g the speed selec tor in a counterclockwise direction draws the tungsten wire from l eft to right in Fig.
34. The tungsten wire then pulls the shutte r-sp eed scale to th e faster- speed cali brat ions. Not ice that you can rotate the wire-hooking nut. Fig. 33, to precisely ali gn the shutter-speed calibrations through the finder.
Certain malfunctions in the electro nic operation might lead you to suspect a
pro blem with the mode switch. For exam ple, suppose that there 's poor brush con
tact or dirty contact surfaces. Poor con
Figure 33
Figure 34
OPE RATION OF THE METERING SYSTEM
From the l op of the camera, Fig. 34, you can see only one of the three IC's — IC1. The other two IC's moun t to the flex circuit at the side of the mir ror cage. IC2, as mentioned earlier, controls the viewfinder LEDs. A hybrid IC — H-IC — contai ns the tran sistor swi tching system that links together the various camera funct ions.
But IC1 does just about eve ryth ing else in the camera. For one thing, it contains the o p amp for the single silicon photo diode (SPD) , Fig. 35. Pushing the release button part way c loses the metering switch to supply power to the circuit ; you
should then measure +3V at pin 1 of IC1,
Fig. 34. Also, the circuit forward biases the silicon photodiode.
Figure 35
SP EED
A AND S MODES
Figure 36
Curren t through the S PD determines the gate bias of an FET (field-effect tran sistor), Fig. 36. You can't as yet see the FET in the camera; i t mou nts t o the underside o f the flex circu it. The FET then changes the linear current changes through the SPD to li near voltage
changes at the amplifier input.
The voltage at the output of the op
amp . Fig. 36, now goes more positive as
the light intensity increases. This voltage
output feeds two circuits — th e memory system through IC1 and the LED display through IC2. Besides seeing the output of the op amp, IC2 receives an input from the diaphragm resistor, Fig. 36. Conse quentl y, all three exposure variables —
the light level, the fi lm speed, and the f/stop — contrib ute t o the LED readout. At the "S " mode, the m inimum-aperture
COMPARATORS FOR LEDS
DIA PH RAG M RESISTOR
— V ^ A A
(0
uj O t o »
ir uj
= UiW
z a uj
to tone
MEMORY SWITCH
MEMORY CAPA CITOR
information also goes to IC2.
IC1 uses the op amp output to charge the memory capacitor , Fig. 35. A s the output of the op amp g oes more pos itive, the voltage measured across the memory capacitor increases. So, if you connect a voltmeter across the memory capa citor, you shou ld get a higher reading as you in crease the light level or set a faster film speed. Ju st push the release button part
way to charge the memory capacitor.
The charge acro ss the memory ca pa ci tor can continu e changing as long as the memory switch. Fig. 36, rem ains clos ed. Fig. 33 points out the memory swit ch in the camera. Just before the mirror
starts to rise, the insulated lever shown in
Fig. 33 drives open the m emory swi tch. Opening the memory swit ch locks in the memory-capacitor charge .
However, you' ll notice in Fig. 36 that the memory-capacitor charge doesn't change with differ ent diaphragm open ings. The diaphragm resistor affects only the meter readout; it has nothing to say ab out the actu al expo sure time. Yet the expos ure -co ntrol circuit m ust k no w the diaphragm s etting in order to program th e proper shut ter speed.
Unl ike most systems, th e XD-11 selects the automatic shutter speed by reading the light through a stopped -dow n ap er ture. With the diaphragm fully open, the SPD sees the maximum amount of light. The indication c ircuit for the LED readout mu st know the selected diap hragm open ing in o rde r to display the p roper shut ter speed at the " A " mo de.
Then, when you push the release but ton the rest of the way, the di aphr agm sta rts closing. As a result, the SPD sees less and less light. Now the volt age out put of the op amp decreases (goes less positive) in proportion to the actua l dia phragm opening.
The vo ltage ac ross the memory capacitor also decreases as the d ia phragm s tops down. Once th e diaphragm reaches the prop er aperture size, the me mor y switch opens. Consequently, the charge remains locked in the memory capacito r. The mem ory-capa cito r voltage, modified by the decreasing ou t put of the op amp, re flects all of the ex posure variables — the light level, the film-speed se ttin g, and the diaphragm opening.
After the memo ry switch opens, the mi rror starts mo ving to the takin g posi tion. The output of the op amp then drops even more. Bu t the actual metering voltag e no longer matters — the m emory capacitor has already memoriz ed the
reference voltage.
The unique metering action can help in tro ubleshooting. Since the indication cir-
cuit takes its l ight reading thro ugh th e
largest ap erture — and the exposure-
control circuit takes its ligh t reading
through the stoppe d-d own aper ture — the two systems can disagree. For example,
suppose there’s a problem wit h the
diaphragm resistor. Al though the LED in dication would then be incorrect, the shut ter would still provid e the proper exposure.
You can get a better idea of the two
separate actions if you operate the
camera on "A " with the lens rem oved. Try rotat ing the diaph ragm-metering ring
un til the LED display indicates a slow
shutt er speed. Then release the shutter.
You'll find that th e shutter delivers an ex
posure time that's much faster than the
readout indicates. Why? You tricked the
readout int o thinking you'd set a small ape rture. But the exposure-control circ uit
knew better.
At the manually calibra ted settings, the meter readout still tells yo u the proper shutt er speed for the light conditio ns. However, the shutte r-speed setting — rather than the op amp — controls t he voltage across th e memory capacitor. As you set faster shutter speeds, the v oltage across the memory capacitor increases.
Earlier, we mentioned the symptom when there's poor contact at one side of
the m ode switch — the s hut ter hangs
open at all functions. You can see why in Fig. 36. If the mode switch fails to make good contact, the me mor y capacitor
ycan't charge. Then, since the shut ter
thinks you' re shooting in total darkn ess, it hangs open.
A d efective memory capacitor or poor cont ac t in the m em ory switch, Fig. 36, results in the same malfu nction. In fact,
any condition whi ch prevents a reference
volt age causes the shutter to hang open.
The block diagram of the shutter-speed
control circuit, Fig. 37, may make the reason appare nt.
The me morized voltage across the memory capacitor provi des the base bias for the current-control transis tor, Fig. 37.
Cur rent t hrough the t ransistor cha rges
the timing capacitor. With a larger (more
positive) base volt age, the transis tor con ducts harder; it then charges the timing capacito r more quickly.
Howev er, if there's no voltage ac ross the m emory c apacitor, th e transistor won't conduct at all. As a resu lt, t he tim ing cap aci tor never reaches the voltage which shuts off the electrom agnet cur rent. And the shutter stays ope n.
Fig. 37 also sh ows the elec tromagnet current path. Consider that you' ve just completed the release-button stroke to release the shutter. As you' ve seen, switch S7 remains closed until the mirror- release combination magnet M2 repels its
armature. Wi th S7 closed, the sw itching transisto r. Fig. 37, turns off; the base of the tr ansisto r connec ts to grou nd.
With the swit ching transisto r turned off, OV appears at each lead of the elec tromagnet. Then , when th e mir ror re leases, S7 opens and applies a positive voltage to the transistor base. The swit ch ing transis tor now turns on, connec tin g the red electromagnet lead to + 3V.
The holdi ng current flows from the electromag net current source, Fig. 37, through the coil, and through the tran
sistor to the positive side of the supply.
Now the energized electromagnet holds the closing blade to keep the shutter open. The current source continues
feeding cur rent to the electromagnet until the timing capacito r charges.
Figure 37
Figure 38
But the timing capacito r can t start charging until the trig ger swit ch (ti ming switch) open s. Fig. 37. As long as the trigge r switch r em ains closed, th e cu rrent-control transistor won't condu ct. The trigger switch c loses whe n you cock the shutter. Then, when the opening-
blade assembly st arts to move, it opens
the trigger switc h.
Now the expansion circuit feeds cu r
rent to the em itter of the current-control tra nsistor. Fig. 37. And the tr ansistor turns on, conducting t he current that charges the timing capacitor. The higher the memorized reference voltage, the mo re quickly the timing capacitor reaches the vo ltage which shuts off the elec
tromagnet current source.
Fig. 38 shows the voltage measured
3V
acros s the t iming ca pacitor. When you
push the release button far e nough to close the metering switch, a slight voltage appears across the timing capacitor. However, the timing capacitor can't charge any further until the trigger swit ch open s. Openi ng the trigger switc h then all ow s the timing capacitor to charge as shown in Fig. 38. When the timing capacitor reaches around 0.5V, it s huts off the current thr ough t he electromagnet to end the exposure.
You can 't as yet reach mo st of th e
components shown in Fig. 36 and Fig. 37.
But you can often pinpoin t the problem from t he top of the camera. So, before covering the complete electro nic opera tion, let's run through the techniques you
can use to check the switches and the elect romagnet without disassembly.
CHECKING THE ELEC TROMAGNET
An o pen electromagn et coil causes the shut ter to deliver only its m echanical speed (1/1000 second o r faster). Al though you'll have to re move the Seiko shutter to replace t he electromagnet, you can c heck the c oil without fu rther dis assembly. Remove the small section o f in sulating tape at the top of the f lex ci rcuit. You can now see the bro wn wire and the
red wire coming from th e electroma gnet.
Check the con tinu ity of the coil by
measuring the resistance between the red
wire and the bro wn wire. You should
measure aro und 300 ohms. Alternately,
you can perf orm a quick sh orting t est to
determine if the electromagnet is good. Try sh orting between the brown wire and ground as you release the shutter. If the
coil is good , the shutter wi ll hang ope n for as long as you maintain the short.
With most electronic shutters, you can check coil continu ity by measuring the voltage a t each electromagnet lead. If you
Figure 39
measu re a volta ge at one lead but not a t the other, the coil must be open. However, y ou've seen that the transistor in series with the XD-11 electromag net re mains off until you release the shutter. So, at the red electromag net lead, you'll measure 0V — not the full battery voltage as you would with most other circuits. You'll also measure 0V at the brown lead.
When you release the shutter, the tran sistor turns on and co nnects the red elec tromagnet lead to positive b attery, Fig.
38. So, with the sh utt er open, you should
measure 3V at the red wire, Fig. 39. But you sho uld still measure 0V at th e brown wi re. The brown wire now con nects to 0V, keeping a 3V pote ntial d ifferen ce
acros s the electroma gnet.
The volta ge at the brown wire s witches high to end the exp osure. If you leave the positiv e voltm eter lead on the brown wire, you can see the voltage switch high. You should see a voltage indication at the end of th e exposure. But the voltage only appears brie fly. When t he mirror returns, switch S7, Fig. 38, once again opens to sh ut off t he transistor. Both elec tromagnet leads then return to 0V.
A poor ground c onnection in t he circuit may also cause the shutter to deliver only its f astest speed. Suspect a poor ground connection if you measure a voltage at the red el ect romag net lead whe n you par tially depress the release button. If you
measure around 2.5V, try retouching the sold er connections to the black ground
wire, Fig . 39. How ever, you may have to
remove the f ront-plate/m irror-cage asse mbly to correct the ground contact. A scre w on the section of flex circuit that mounts to th e mir ror cage makes the ground connection through the camera body.
If you measure the full 3V to the red wire
and the brown wire, the switching tran
sistor may be shorted. Fig. 38. A 3V reading could also indic ate a problem with the elec trom agne t current source. Both components are inside H-IC, the hybri d IC on the side of the mirror cage. You'll have to remove the front-p late/mirror-cage
assembly to replace the IC.
CHE CKING THE METERING SWITC H AND THE RELEASE SWITCH
Both the metering switc h and the release switch are a t the back of the front- plate as sembly. A s yet, you can 't reach
the switches. But yo u can reach the switch connections for troubleshooting.
The mete ring switch c onnect s to the green wire, and the release switch con nects to the oran ge wire, Fig. 39.
Fig. 40 s hows the portion of the schematic t hat includ es th e two switches. As you st art pushin g the release button, the m eter ing swit ch S5 closes. The
metering swit ch t urns on transistor T1,
applying the positive battery volta ge to
pin 1 o f IC1 and to pin 2 of IC2.
Pushing the release button the rest o f
the way closes th e release switch S3. The release switch now tells the elect ro magnetic release circuit to release the mir ror. Also, the power-holding circuit —
trans istor T11 in Fig. 40 — turns on. T11
now keeps transistor T1 conducting. So, even if y ou allow the release button to return, the circu it con tinues to operate.
Tra nsistors T1 and T11 are both inside
H-IC on the side of the mirror cage. Diode D2, a transis tor conn ected as a d iode. Fig. 40, is also inside the hybrid IC. You might sus pect a prob lem in this por tion of the circu it if th e camera draws pow er constantly — even though you haven’t depressed the release button.
What if the metering switch S5 fails to
make contac t? Obviously, the LEDs will not turn on when you partia lly depress the release butto n. Yet, thanks to the power-
holding circuit, the LEDs will turn on when you fully depress the release button. With a defective release switch S3, the shutter won't release at the electronically co n trolled settings.
To check the metering switch , measure the vo ltage at the green wire, Fig. 39. You should measure around 2.5V. Wh en you depress the release b ut to n part way, you should measu re 0V at the green wir e. If the voltage doesn't drop to 0V (ground), the me tering sw itch isn't making good contact.
Alternately, you can check th e metering switc h by connecting an ohmmeter be tween the green wire and gr ound ; you should measure direc t conti nuity when you push the release button part way . Or you can simp ly sho rt the green wire to ground. C onnecting the green wire directly
Loading...
+ 39 hidden pages
Buy Points How it Works FAQ Contact Us Questions and Suggestions Privacy Policy Cookie Policy Terms of Use