Sencore TC154 Service Manual

TC

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MIGHTY MITE

TUBE CHECKE R

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SENCORE SERVICE

426 S. WESTGATE DRIVE, ADDISON, ILLINOI S 60101

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M a n u a l .

SAFETY’ P RECA UTION S

When test ing e lectronic equipme nt, there i s alw ays a danger present. Unexpect ed
high vo lta ges can be pres ent a t unusual lo cations in de fective equipment. The t ec h
nic i an should bec ome familiar with the device that he i s wo rking on and observe the
follow ing pre cautions.

1. An isolation transformer should always be used on equipment hav ing the chassis
tied to one sid e of the AC po wer l in e.

2. When ma king test lead connections to h igh vo ltage point s, remove the power, i f
this cann ot be d one, b e sur e to av oid contact with other equ i pment or metal ob 
jects. Place o ne hand in yo ur poc ket as a safety pre cauti on and stand on an in
sulated floor to reduce the possibil ity of s hoc k.

3. Disc ha rge filter cap acit ors b efore connec ting tes t l eads to the m. Capacitors c an
stor e a charge that co uld be dangerous to the tec hnician.

4. Be su re your equipment is in good order. Broken or frayed test leads can be
ext re m el y d angerous and can e xpo se the t echnician to dangerous potentia ls.

5. Remov e the test leads i mmediately after the test has be en completed to reduce

the po ss ibil ity o f shock.

6. Do not work alone when w orki ng on hazardous circuits. A l ways have another
perso n close by in case of ac cident. Remem be r, even a minor shock ca n be the
cau se o f a m ore seri ous ac cident, suc h as falling against the equipment , or comin g
in contact with higher voltages.

TABLE OF CONTENTS PAGE

SAFETY PRECAUTIONS....................................................................................................

DESCRIPTION......................................................................................................................

SPECIFICA TIO NS

Tests the Mighty M i te will make

OPERATION..........................................................................................................................

Acqu aintin g yourself with the Mighty M ite

Operating the Mi ghty M ite .....................................................................................

Add i tional Tes ts and Func tions of the M i g h ty M i te

Setting up the Might y Mite for new tubes

Exa mple o f s etting up the Mi ghty M ite...............................................................

MAINTEN ANCE...................................................................................................................

Disassembl y In structi on s

Emissi on Calibrat ion................................................................................................

Circ uit d escript ion

Tr oub l e chaxt...............................................................................................................

Parts L ist......................................................................................................................

Ser vice and Warranty................................................................................................

FIGURES

Fi g. 1 - 9QL T ube bas i n g .....................................................................................

Fig . 2 - Cal Mod ule Schematic..............................................................................

Fi g. 3 - P. C. Board la y out

Fig. 4 - Schemati c d ia gram .................................................................................

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INSTR UCTIO N MANUAL FOR THE SENC ORE TC154

MIGHTY MITE VI TUBE TE STER.

DES CRIPTION

The new Senco re Might y Mite VI r eprese nts a unique brea kthrough in tube testers .
The M ighty Mite VI is compl etely solid state using the FET in a balanced b rid ge for
an i nstant on checker. This new outs tanding fe ature means that no time is wasted
wa i t ing f or the checker to warm up and stabil iz e before accurate testing c an begi n.
The new Migh ty Mite is ready as s oon as itis turnedon. A full load cat hod e cur rent
ch eck, high se nsitivi ty grid leakage check, and the famo us Se ncore Stethoscopi c
shorts test ma ke this the ideal check er for service work and the man o n the go.
Check the fe atures of the Mighty Mi t e below :

* Full load cathode current ch eck to pick out the weak tubes othe r checkers miss.
* 100 megohm grid leakag e sensitiv ity to find the tough dog tubes f ast.
* Steth osc opi c sh or ts test of 300K to pic k out true shorts in the tube.
* Burnout pro of meter , ev en if a shorted tube is tested backwa rds.
* FET bal anced bridge c ircui tr y for instant on action and greater accura cy .
* All steel c ase f or ma xim um pr otectio n and g ood looks for the life o f the checker.

SPECIFICATIO NS

Cathode Emission Test : Fu ll load curren t draw n throug h tube up to 120 mA . Max
applied voltage, 40 VAC RMS.

Grid Leakage Test: Good a rea, in finity to 200 megohm s, ? ar ea , 200 to 100 megohm s

and the Bad area 100 megohm s o r l e ss.

Shor ts Test: 300,000 oh ms or less will caus e s horts li ght to come on. Maxim um

applied voltage, 40 VAC RMS.
Power: 105 to 12 5 VAC, 50/ 60 Hertz at 32 watts maximum.

TESTS THE M I GHTY MITE WILL MAK E

Cathode Emission: The Mi g hty M i te tests all tubes at near their full ra ted cathode
curr ent level for the best emi ssion c heck. Th is is very import ant as many te ster s

do not test at this high lev el of cu rren t and c an pass many tubes as g ood that wil l not

work satisfactor ily in the ci rc uit. Thi s test is ver y important o n high power tubes
such a s rect if ier s, horizont al and sound output tubes.
Grid Le akage T est: Gr id lea kage or grid emi ssion in a tube can upset many c ircuits,
incl udin g the AGC, Chrom a, Video , Sy nc, ando th er s. Grid cur rents as low as one
microam pc an change the bias in th ese circui ts causing many headaches. TheM igh ty
Mite det ec ts grid cu rren t as low a s one-half a mic roamp or 1 00 megohms to pi ck out
these tr ouble making tu bes that ar e ofte n m issed by oth er tube checker s. As soon
as the tube is warm en o ugh to indicate ca thode emissi on, the gri d leaka ge test can
be pref ormed.

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Shorts Test: T h e Sencore "S teth oscopic " shorts test pic ks out t rue sh orts betw een
el eme nt s in the tube of 300,000 oh ms or les s. Above this val ue, the sho rt s light may
flicker indicat ing a high re sis tance s ho rt in the tube. The a ppl ied v oltage is kept be
low the 50 volt maximum to pre ve nt damage to frame gri d tubes andnuv istors . Th is
prevents the Migh t y Mite from damaging tubes and introdu cing a sh or t in the tube that
was not there befor e.

OPERATION

ACQUAINTING YOURSELF WITH THE MIGHTY MITE
The Mighty Mite is compose d of four setup control s and four push button switc hes.

The four controls marked A - FILAME NT, B - LOAD, C - SETUP, and D - SETUP
are s et accor ding to the in for ma tion in the setup chart. The tube is inserted into
on e of the thi rte en soc kets num bered fr om on e to thirte en as ind ica ted in the setup
chart. Th e Grid Cap lead, located in the low er c or ne r of the fr ont panel, is pla ced
on tubes ha ving a gri d or pla te cap. The d esired function is selecte d by depres sing

the button corre sponding with t he test de sired , Emission, Short s, or Gr id Leakage.

The tests can be made in any orde r witho ut damag e to the che cker, even i f th e tube

under tes t is s horted.

OPERATING THE MIGHTY MITE

1. Plug the AC lin e c ord into a 105 to 125 VAC, 50 to 60 He rtz rec eptacle.

2. Locate the tube in the s etup chart in the cov er. The tub es are listed numerically
and alphab etical ly. L ookin g to the r ight of th e tube number, note the s etup in
formation for the cont ro ls A, B, C, D, and socket n umber. Some tubes have
more than one li sting indicating the tube has more than one section to be tested.
Each s ecti on of a m ult iple section tube is tes ted separ ately.

3. Set the controls A, B, C, and D as i ndicated in the se tup chart and inse rt the
tube in t o the socke t listed. W h ere more than one setti ng is listed, make the tests
on each setting . The shorts test need be mad e only once on most tubes.

4. Depress the SHORTS button and check the METER ZERO adj ust for aO indication

on the meter. Th en rotate the "D" swit ch through all its positi ons noting the
SHORTS light. The light will glow if a sh or t of 300,00 0 oh ms or less is present .
If th e ligh t does glow , be sur e it glows on both elem ents. In some tubes, short s
e xist that do not a ffect the operatio n of the tube are marked with an asterisk (*) in
the tube chart. If the SHORTS lightglows on the m arked points o f the "D" swi tch,
then no shorts that will affect the tube operation are present. If the SHORTS light
gl ows on a poin t other than that m arked in the setup book , then a short is presen t.
Some tubes may show a short on on ly one pin of the tube. Th is is because the
suppressor grid is tie d to the cathode of the tube in ternal ly and may indicate a
short on only one positio n of the ”D" s witch. If the short is p resent on two or
more po sitions, than a shortd oes e xist. The tube should be rej ec ted for sho rts,
except if they are indicated in the se tup book. NOTE: A few tubes marked with
an aster is k i n the setup book and ind ica ting a s havin g a nor ma l short m ay not
show any shorts on the M i ghty Mite. This is because some tube manu factu rers
use the s pa re base pins f or extra inter nal connect ions, whereas other man ufa c
turer s of the same tube may not.

5. If th e tube passes the SHORTS test, depress the EMISSION button and read the
em iss ion qua l ity o f the tube on the top scale of the meter . A tube indi cat ing in
the quest ionab le ar ea of the meter may or m ay not b e reject ed depe nding upon
you and your cus tomer .

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