Tektronix Type 82 PLUG-IN Instruction Manual page 36

Maintenance—Type 82
TABLE 4-5
Trouble Isolation Procedure
Symptoms
Checks To Make
Possible Causes Area at Fault
6. No dual-trace switching; get only
one trace. If MODE switch is set to
CHOP., switching transients* appear
on the trace. As one of the VERTICAL
POSITION controls is rotated, ampli-
tude of transients appears to change.
Check D566 or D576 for short or open. Check for trouble in the
Switching Circuits. Refer to
7. No alternate-mode switching; get
only one trace. Other modes are nor-
Check for shorted D580 or open D585.
Check for trouble between pin 7 of the inter-
connecting plug and D585.
Check ALTER. SYNC SENS. adjustment.
Check Blocking Oscillator
@590 and B.O. Bias EF Q583
stages. Refer to Part Il.
8. Alternate mode operates at one of
the chopping rates (depending on set-
ting of CHOP RATE switch).
Check ALTER. SYNC. SENS. adjustment.
Check B.O. Bias EF Q583 stage.
Refer to Part Il.
9. No alternate-mode switching; get
only one trace. In chopped-mode op-
eration, get improper chopped-rate
switching. With CHOP RATE Switch
set to 100 kc, the rate is about 118 kc;
with switch set to 1MC, the rate is
Check for shorted D586.
Check for trouble in the Block-
ing Oscillator Q590 or B.O.
Bias EF @583 stages. Refer to
tion. Chopping occurs at a rate of
about 70 ke if CHOP RATE switch is
set to 100kc, and about 830kc if
Check for open D580 or shorted D585.
(D585 shorted causes a very slight decrease in
chopping rate.)
Check for trouble in the Block-
ing Oscillator Q590 or B.O.
Bias EF @583 stages. Refer to
11. Improper chopped-mode opera-
switching transients** on the traces
when they are superimposed.
Check for an open shunt diode in the diode
gate: D501, D506, D502 or D507.
Check for trouble in the diode
tion. Trace segments in affected chan-
tilted. Distortion exceeds Y%. mm in
Check for a shorted shunt diode in the diode
gate of the channel affected. For example,
D501 or D502 in channel A; D506 or D507 in
Check for trouble in the diode
13. Improper chopped - mode opera-
tion. Channels do not switch alter-
Check for shorted D581.
Check for trouble in the Block-
ing Oscillator Q590 or B. O.
Bias EF Q583 stages. Refer to
14. No chopped-mode operation when
only one trace. Inadequate Position-
appear normal except for abnormal
Check for a shorted series diode in the diode
gate of either channel: D503, D504, D508 or
Check for trouble in the diode
gate.
Check for open D586,
Check for trouble in the Block-
ing Oscillator Q590 or B.O.
Bias EF @583 stages. Refer
to Part Il.
16. Low gain, both channels. Gain
switch set to X1***.
Check for defective tubes: V524, V534, V544.
Check for leaky capacitors: C525, C526, C535,
C536, C539, C545, C546 or C549.
Check for trouble in the Out-
put Amplifier stage. Refer to
Part IB.
4-12