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SYMPTOM
Amplifier causes power line fuse to
blow. Power line
fuse blows again
with VII & V12 out of their sockets.
Amplifier causes power line fuse to
blow. Power line fuse
does not blow
again with VII &
V12 out of their
sockets.
Any or all tube filaments not lit.
Output tube bias too high (result-
ing in distorted output waveform).
DC voltage at Vl1, V12 cathodes
(pin 3) is incorrect as specified
below.
a) No
voltage.
b) High voltage.
c) Low voltage.
Excessive hum on mag. phono tape
head or mic.
Excessive noise on mag. phono
tape head or mic.
Sustained oscillations.
Sustained microphonicson mag.
phono, tape head or mi c.
Hum on all inputs.
TROUBLE-
SHOOTING CHART
CAUSE
REMEDY
Line cord, J16, primary or high voltage
Replace or repair.
secondary windings of T1 shorted internally
or externally (wiring).
VII, V12, C39)' V7, va, V9,
VI0, or T2
T3 primary shorted internally or
exter-
nally.
Open tube fil ament.
Open lead from 6. 3V winding of T1.
6 3 V winding of T1 open.
Open
R56, R57.
Defective VII or V12.
C39 shorted internally or externally.
Connection from C39 to pin 3 of VII
& V12 broken.
Connection to center tap of h. v. second-
ary winding of T1 open.
Output tubes V7, VS,
V9, VI0 over-
biased or not drawing current. May re-
sult from open
R56 or R57.
Excessive current drain in amplifier.
Defective VII, V12.
VI or V2 defective.
FiI.
leads dressed toa close to grid
lead.
Tube shield not making electrical con-
tact to base or base not
making elec-
trical contact to chassis.
Shielding and grounding of wiring to
input jacks not exactly as instructed
and shown in drawings.
VI and V2 and contacts dirty.
Poor dress of output transformer T2 or
T3 leads.
VI or V2 defective.
V3 or V4 defective, not properly
shielded, or dirty sockets and contacts.
Dress of power transformer T1 leads.
Replace or repair.
Replace or repair.
Replace or repair.
Replace
Replace or repair.
Repair
Repair
Replace, repair, or see trouble-
shooting typical tube stage.
See trouble-shooting typical tube
stage.
Replace
Replace
Dress fit. leads
away from grid lead.
Check and correct.
Correct
Clean throughly with carbon
tetrachloride.
Dress all input leads and T3 leads
away from each other. Keep T3
leads away from input jacks.
Replace
Replace, correct
, or clean.
Correct
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Troubleshooting
