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Troubleshooting - 3
29
Continued from
sheet 4
A
1U306B-2,
OV_Detect*, High?
No
U306B-7 < pin 8?
Yes
Check U306B, A2
Check R349, R351,
R356
Yes
No
A
1R438,
OV_SCR*, +0.6V?
Yes
Check R441, Q318B,
A
2, Interface Board
No
Check A1CR342,
Q318A, B & D and
associated
components
Yes
Note: OV_SCR* is
normally a pulse that
goes low for 5us to trip
the OV SCR, CR342.
Connect a DC coupled
scope across the
output and press
Protect Clear several
times while observing
the scope
Pulses high?
Go to "Troubleshooting
High Output Voltage"
(sheet 12)
Yes
No
U306B-8 3.8V?
Check OV_Prog,
Imon_Comp, C335,
R350, R354
No
Figure 3-1 Sheet 5. OV at Turn-On (continued)