Preregulator Troubleshooting - HP 6269B Operator’s, Organizational, Direct Support And General Support Maintenance Manua L

STEP ACTION
2 Connect oscilloscope be-
tween TP85 (+) and TP103
(-).
1
Connect oscilloscope be-
tween TP80 (+) and TP103
3
(-).
Connect oscilloscope be-
tween TP82 (+) and TP103
4
( - ) .
5 Connect oscilloscope be-
tween TP81 (+) and TP103
(-) .
5-62 DISASSEMBLY PROCEDURES
5-63 The following seven paragraphs describe
procedures for removing and disassembling the
five subassemblies in this supply (A1 main circuit
board, A2 RFI assembly, A3 interconnection circuit
board, A4 heat sink, and A5 front panel). These
procedures are referenced throughout the manual
wherever necessary. For example, in the instruc-
tions for converting the supply to 115Vac opera-
tion, reference is made to the RFI assembly remov-
al procedure in order to allow access to the bias
transformer (A3T2) primary connections.
5-64 Main C ircult Board (Al) Removal. To remove
the main printed circuit board, proceed as follows:
a. Unplug unit and remove top cover of
supply.
b. Remove six hold-down screws visible on
component side of main circuit board (arrowed "A"
through "F" in Figure 7-1 O).
c. Unplug board from receptacle mounted on
interconnection circuit board by gently pulling on
finger hole in opposite end of circuit board. Only
finger hole should be used to remove board; do
not pull on beard-mounted components to aid re-
moval. Care must be taken that rear barrier strip
clears opening in rear panel.
5-65 Front Panel (A5) Removal. To remove the
front panel, proceed as follows:
a. Unplug unit, turn supply upside down,
and remove four screws holding handlers to front
panel.
Table 5-7. Preregulator Troubleshooting (Continued)
a. Normal waveform.
b. Little or no voltage.
I
a. Amplitude incorrect.
b. Period incorrect.
a. Amplitude, dc reference or
period incorrect.
a. Amplitude, dc reference or
period incorrect.
RESPONSE
b. Front panel may now be swung outward,
hinging on wires to LINE circuit breaker. Access
is provided to all panel-mounted components.
5-66 Main Filter Capacitor Bank Removal. To re-
move the main filter capacitors (Cl 01 through
C104), proceed as follows:
a. Unplug unit, remove top and bottom cov-
ers of supply.
b. Remove one long screw and hold-down
bracket on top of supply (arrowed "A" in Figure
7-3), and one long screw and hold-down bracket
on bottom of supply (arrowed "A" in Figure
7-4).
c. Sufficient lead length is provided to al-
low capacitors to be lifted partially out of instru-
ment.
5-67 RFI Assembly (A2) Removal. To remove the
RFI assembly, proceed as follows:
a. Unplug unit, turn supply upside down,
and remove bottom cover.
b. Remove four screws holding RFI heat
sink to mounting brackets (arrowed "A" through
"D" in Figure 7-5).
sible through holes in chassis flanges.
. Lift out RFI assembly and turn over.
C
d. Remove four screws holding cover to heat
sink (screw holes are arrowed "A" through " D" in
Figure 7-1). This allows access to A2R1, A2C1,
and A2L1A/A2L1B with its jumpers for 115/230 volt
operation.
. Remove four screws holding A2L1A/A2LlB
mounting bracket to heat sink. (Two of the screws
5-15
TM 11-6625-2958-14&P
PROBABLE CAUSE
a. Defective T70.
b. Defective Q72, Q73,
CR76, or C71. pro-
ceed to Step 3.
a. Defective Q71, C70,
C72, CR74, CR75,
R82, R75, or R78.
b. CR78 defective. Pro-
ceed to Step 4.
a. Defective CR82,
CR84, CR79, CR80,
CR77, CR78. Check
R87.
a. Defective CR81,
CR83, R86, R83,
C73.
,
Two of the screws are acces -