Orban 8200 User Manual
OPTIMOD-FM 8200 MAINTENANCE
Section 4
Maintenance
page contents
4-2 Routine Maintenance
4-3 Getting Inside the Chassis
4-3 Front panel — open and close
4-4 Rear panel — remove and replace
4-5 Input Filter Board — remove, repla ce
4-6 D-Connector Board — remove, repla ce
4-6 Power Supply — remove, replace
4-1
4-7 In-System Testing (“Proof of Performance”)
4-8 Monophonic Performance Verification
4-9 Stereo Performance Verification
4-15 Field Audit of Performance
4-19 Field Alignment
4-20 Prepare the Unit
4-20 Test Power Supplies (optional )
4-22 Calibrate and Test Card #1 (Analo g Input /O utpu t Circuitry)
4-24 Calibrate and Test Card #2 (Ana log Stereo Baseband En cod er)
4-28 Figure 4-1: Separation Scope Trace
4-29
Return OPTIMOD-FM to Service
CAUTION
The installation and servicing instructions in this manual are for
use by qualified personnel only. To avoid electric shock do not
perform any servicing other than that contained in the Operating
Instructions unless you are qualified to do so. Refer all servicing
to qualified service personnel.
4-2
MAINTENANCE OPTIMOD-FM 8200
page
Routine Maintenance
The 8200 OPTIMOD-FM Audio Processor uses highly stable analog and digital circuitry
throughout. Recommended routine maintenance is minimal.
1. Periodically check aud i o level an d gain reduction meter read i ng s.
Become familiar with normal audio level meter readings, and with the normal performance of the G/R metering. If any meter reading is ab normal, see Section 5 for troubleshooting information.
2. Listen to the 8200’s output.
A good ear will pick up many faults. Familiarize yourself with the “sound” of the 8200
as you have set it up, and be sensitive to changes or deteriorations. But if problems arise,
please don’t jump to the conclusion that the 8200 is at fault. The troubleshooting
information in Se ctio n 5 wi ll he lp you det ermine if the pro blem i s wi th OPT IMOD-FM
or is somewhere else in the station’s equipment.
3. Periodically ch eck fo r corr osi o n.
Particularly in humid or salt-spr ay envir onments, ch eck for co rrosion at the input an d
output connectors and at those places where the 8200 chassis contacts the rack.
4. Periodically check fo r lo ss of gr ou nding.
Check for loss of grounding due to corrosion or loosening of rack mounting screws.
5. Clean the front panel w hen i t gets so i l ed.
Wash the front panel with a mild household detergent and a damp cloth. Stronger
solvents should not be used because they may damage plastic parts, paint, or the
silk-screene d lettering (99% isopropyl alcohol can be safely used).
OPTIMOD-FM 8200 MAINTENANCE
Getting Inside the Chassis
Access the AC POWER switch by opening the 8200’s front panel (see below). The
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AC POWER switch is located on the power supply module to the right of the chassis.
The VOLTAGE SELECTOR switch and the two fuses are on the 8200’s rear panel.
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Access the circuit cards by opening the 8200’s front panel.
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Most set-up and adjustment of the 8200 can be done from the front panel without
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accessing the interior of the chassis. Alignment of the 8200 requires access only
to the front and rear panels and to those interior parts of the unit behind the front
panel. Almost all servicing can be done without removing either the top or bottom
covers.
Further disassembly of the 8200 may be required for some service procedures.
For access to: See page:
4-3
Behind front panel 4-3
Behind rear panel 4-4
Input Filter Board 4-5
D-Connector Board 4-6
Power Supply 4-6
For best RFI protection, replace all screws and tighten them firmly. If screws are lost,
replace them with screws of the same length (longer screws may cause mechanical interference or inter nal short circu its). Most screw s used in the 8200 are equipped w ith integral
lockwashers fo r secure fastening. I f a pan head screw is subs tituted, use an internal-star
lockwasher. All sc rews are steel, plated with zinc.
Front panel — open and close
To open:
1) Disconnect power to the unit.
WARNING: Hazardous voltage is exposed with the fr ont pa ne l open an d
the power ON.
2) Remove the six Philips head screws at the top and bottom of the front panel with a Philips
screwdriver.
3) Grasp the edges of the panel, pull slightly forward, and, while holding the panel vertical,
guide it forward a nd downw a rd on its s up ports . The n r ota te th e top of the panel toward
you and down until it rests on its supports.
4-4
MAINTENANCE OPTIMOD-FM 8200
To close:
1) Check that the internal
AC POWER switch is set to ON (depressed).
2) Rotate the panel until it is vertical. Raise the panel while guiding it in on its supports.
3) Fasten the six screws that secure it in place with a Philips screwdriver.
Rear panel — remove and replace
To remove:
1) Disconnect the 8200 and remove it from the rack.
It is not practical to remove the rear panel when the 8200 is mounted in a
rack.
2) Set the unit upright on a padded surface with the rear panel facing you.
3) Remove the four screws holding the power supply.
4) Remove the sixteen screws that hold the rear panel to the chassis.
Leave about six inches (15c m) between the re ar panel and the edge of your
work surfac e.
5) Very carefully pull the rear panel about 3⁄4-inch (2cm) toward you until the internal
connectors become unplugged.
The internal connec tors are de licate and easily damaged. Be sure to pull th e
panel directly and straight away from the chassis.
Take care to n ot damage th e conne ctor pins on the Motherbo ard while the y
are expose d.
6) Tilt the top of the panel slightly downward and disconnect the cables that plug into the
Motherboard.
To replace:
1) Tilt the rear panel up until it is nearly vertical and plug the two or three cables (depending
on your unit’s Model #) into the Motherboard.
2) Very carefully line up the three connectors on the input Filter Board and the two or three
connectors on the D-Connector Board with their mating connectors on the Motherboard.
Be sure that all six connectors are properly engaged and push the rear panel in to seat the
connectors.
The connectors are de licate and easily damaged. Do no t force them.
Take care that no wires are pinched between the pane l and the ch assis.
If you encounter difficulty, you may remove the top cover to gain visual
access to the connectors. When replacing the top, be sure that the circuit
cards and the card guide s ar e aligned.
3) Replac e all twenty screws previously removed.
Do not tighten any screws until they are all loosely in place.
OPTIMOD-FM 8200
4) Return the 8200 to its rack, connect and ground unit.
MAINTENANCE
Input Filter Board — remove, replace
To remove Input Filter Boa rd:
1) Remove the rear panel.
See page 4-4.
2) Remove the hex nuts f rom the SCA input, composite 1 outpu t, and compo site 2 output
BNC connectors.
3) Remove the 4-40 machine screw between the left input and output XLR connectors.
4) Using a small screwdriver, unlock each XLR connector insert.
The lock is accessible through a small hole in the face of the connector.
Turn the lock
5) Remove the Input Filter Board by gently pulling the board away from the panel.
To replace Input Fil ter Boa rd:
1
⁄4 turn counter-cloc kwise to re lease.
4-5
1) Place the board in position over the panel and insert the XLR and BNC connectors into
the panel.
Be sure that the washers on the BNC connectors are in place.
2) Lock the XLR connectors
Turn the lock 1⁄4 turn clockwi se .
3) Replace th e screw between the left inpu t and output XLR connectors and re place the
BNC connector hex nuts.
4) Replace the rear panel.
See page 4-4.
4-6
MAINTENANCE OPTIMOD-FM 8200
D-Connector Board — remove, replace
To remove:
1) Remove the rear panel.
See page 4-4.
2) Remove the six hex nut jackscrews holding the D-connectors to the rear panel.
3) Remove the one 4-40 screw holding the D-Conn ec tor Board to the rear pane l.
To replace:
1) Position the boa rd with th e D-c onnecto rs thro ugh the rear pane l. Replac e the o ne 4-4 0
screw and the six jackscrews.
Do not tighten any screws until all screws are loosely in plac e.
2) Replace the rear panel.
See page 4-4.
Power Supply — remove, replace
To remove:
1) Disconnect the line cord.
2) Remove the four screws holding the power supply to the rear panel.
3) Open the f ront panel.
See page 4-3.
4) Grasp the power supply module (located at the far right of the chassis) by its handle and
pull it forward u ntil it un-mates from its connector. Then slide the module out of the
chassis to free it.
To replace:
1) Align the power supply module with its guide rails and push it back until it mates firmly
with its connector on the Motherboard.
2) Replac e and tighten the four screws that mount the power supply to the rear panel.
3) Close the 8200’s front panel.
See page 4-3.
Be sure that the internal
4) Re-connect the line cord.
AC POWER switch is set to ON (depressed).
OPTIMOD-FM 8200 MAINTENANCE
In-System Testing (“Proof of Performance”)
The FCC (Federal Communications Commission — U.S.A.) no longer requires periodic
Proof of Performance measurements for FM stations. However, many stations will still wish
to make periodic e quipment performan ce measurements to ensure tha t their transmission
system is working correctly and that they comply with all government regulations. The text
below provide s the gene ral info rmation that is ne eded to per form measu remen ts verifyin g
the performanc e of a transmission sy stem including the 8200. I nstructions for bench -top
verification of 820 0 performance outside of the tra nsmission system are found be low in
Field Audit of Performance starting on page 4-15.
These instruction s are written w ith the assumption that the analog inputs and outputs are
used. If the optional digital I/O is used instead, follow the procedures below by analogy —
you will have to supply digitized test tones.
The NAB Broadcast and Audio System Test CD provides a good source of digitally-
generated te st ton es o n co mpa ct dis c. N o te, h ow e ve r, that thes e ton es are at a 44.1kH z
sampling rate. They cannot be directly applied to the 8200’s optional 8200D/32
AES/EBU digital input, which only accepts audio d igitized at a 32kHz sample rate. They
can be applied to the 8200’ s AES/EBU inp ut if you are u sing the 820 0D/SRC in terface
card. This test CD is available from:
4-7
NAB Services
1771 N Street N.W.
Washington, D.C. 2003 6, U.S.A.
order: (1) (8 00) 368-5644
Required Equipment:
Ultra-low distortion sine-wave oscillator/THD analyzer/audio voltmeter
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(With verified residual distortion below 0.01%. Sound Tec hnology 1710B;
Audio Precision System One, or similar hig h-pe rf or manc e syste m. )
(The NAB Broadcast and Audio System Test CD is an excellent source
of test signals when used with a high-q ua lity CD pla ye r. )
Precision FM modulation monitor or demodulator
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(Belar FMM-2; TFT 844, or similar.)
Precision stereo monitor or demodulator
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(Belar FMS-2; TFT 844, or similar.)
optionally, baseband spectrum analyzer, 0-100kHz
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(Tektronix 5L4 N plug-in with 5 111 bistable stora ge mainfram e or similar.)
4-8
MAINTENANCE OPTIMOD-FM 8200
Monophonic Performance V erifi cation
Monophonic performance verification is straightforward. Put the 8200 in MONOL Mode,
recall the test preset BY BYPASS, and drive the left OPTIMOD-FM input with the test
signal. Suff icient head room is av ailable to modula te well beyo nd 100% at all f requencies
from 50 to 15,000Hz.
1. Prepare the unit.
A From the IDLE screen, press SYSTEM SETUP button, then press I/O CALIB to
access the
B Scroll to the MODULATION TYPE parameter and set to MONOL.
C Press ESC to return to the IDLE sc re en.
D From the IDLE screen, press RECALL PRESET button to access the RECALL
PRESET screen.
E Scroll to BY BYPASS.
I/O CALIB screen.
F Press RECALL& MODIFY button to put BY BYPASS on the air and access its
screen controls.
This test tone defeats all compression, limiting, and c lipping, but le aves the
15kHz low-pass filter in the signal path.
G Set the controls, as follows:
BYPASS GAIN dB +6
30Hz HPF OFF
This scales the gain through the 8200 so that a 50Hz tone applied to the
analog input at 6dB below the A-I CLIP LVL dBu that you preset (in the
I/O CALIB screen) produces the following output levels:
a) at the left and right analog outputs: the level in dBu that you preset a s
the A-O MAX LVL dBu (in the
screen);
b) at the optional AES/EBU digital output: 2.76dB below the maximum
digital word on both left and right channels (8200D/32 Card) or the
level that you preset as the D-O 100% LVL dB (in th e
I/O CALIB CONTROL
I/O CALIB
CONTROL screen), if you’re using the 8200D/SRC I/O Card; and
c) at the output of the optional stereo encoder (analog or digital): 100%
monophonic modulation.
Please note that OPTIMOD-FM’s fr equency re sponse drops o ff extre mely
rapidly above 15kHz. If the test oscillator is mis-calibrated, OPTIMODFM may appear not to mee t its fre quency respo nse sp ecific ation at 15kHz .
Before blaming OPTIMOD-FM, measure the output frequency of the test
oscillator with an accurate counter to make sure th at it is actually producing
15kHz, and not some slightly high er fre qu en cy .
H Press ESC to return to the IDLE screen.
OPTIMOD-FM 8200
MAINTENANCE
Stereo Performance Verification
Many stations may wish to verify that they meet the requirements of the old part 73.322 of
the FCC Rules (which was deleted in 1983 , and which referred to st ereo performan ce). Part
73.322 referred to the performance of the transmitter only (starting with stereo encoder input
terminals), and measurements may be made by connecting the test oscillator directly to the
OPTIMOD-FM main aud io inputs. Fol lowing is a n outline o f the appropr iate measurem ents
and how to perform them.
1. Prepare the unit.
A From the IDLE screen, press SYSTEM SETUP button, then press I/O CALIB to
access the
B Scroll to the MODULATION TYPE parameter and set to STEREO.
C Press ESC to return to the IDLE screen.
D From the IDLE screen, press RECALL PRESET button to access the RECALL
PRESET screen.
I/O CALIB screen.
4-9
E Scroll to BY BYPASS.
F Press RECALL& MODIFY button to put BY BYPASS on the air and access its
screen controls.
This test tone defeats all compression, limiting, and c lipping, but le aves the
15kHz low-pass filter in the signal path.
G Set the controls, as follows:
BYPASS GAIN dB +6
30Hz HPF OFF
This scales the gain through the 8200 so that a 50Hz tone applied to the
analog input at 6dB below the A-I CLIP LVL dBu that you preset (in the
I/O CALIB screen) produces the following output levels:
a) at the left and right analog outputs: the level in dBu that you preset a s
the A-O MAX LVL dBu (in the
screen);
b) at the optional AES/EBU digital output: 3dB below the maximum
digital word on both left and right channels; and
c) at the output of the optional stereo encoder (analog or digital): 100%
monophonic modulation
d) at the output of the optional stereo encoder (analog or digital): 100%
modulation including pilot tone.
[NOTE: Because of the “interleaving” effect in the pilot tone stereo
system, the peak modulation of the com posite baseban d sign al is appr oximately equal to the higher of the peak modulations that would have been
caused by a given channel’s (left or right) driving the system alone. This
is an analog OR f un ctio n; there is no summa tion . The relatio nship i s exact
when the pilot tone is not present; however, when the pilot tone is present
the peak composite modulation increases about 2.8% when first one, and
I/O CALIB CONTROL
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