Troubleshooting - HP AM-4380/U 5261A Technical Manual

leads in place. Heat may be applied to either side of
board. A heat sink (longnose pliers, commercial heat-
sink tweezers, etc.) should be used when replacing
transistors and diodes to prevent conducting excessive
heat from the soldering iron to the component.
Trouble Symptom
No output to Counter or 50 Ω OUTPUT
jack
Low Video Amplifier gain
Output low at frequencies near 10 cps
Output Iow at frequencies above 100 kc
Output noisy
the separation from the board of the round conductor
pads against board and solder replacement component
lead to conductor pads on both sides of the board.
TABLE 5-3. Troubleshooting
DC voltages from Counter, FET A1Q1 dead,
A4Q4 shorted, P6(1) or J2 shorted
AQ1 weak, A3Q1-A3Q6 weak, A4R5 increased
value
A4C6 open, A1C1, A3R18 increased value
A2C1 changed value, high frequency trimmers
A3C4 and A3C11 not correctly adjusted
A1Q1 noisy poor ground connection at P6(3),
A3C5 ,or A3C12 changed value
5-4
d. Through-hole plating breaks are indicated by
Possible Cause
Model 5261A
Section V
Table 5-3