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Service Addendum 15
OV Will Not Fire Troubleshooting
Figure 3-6. OV Will Not Fire Troubleshooting
"OV Will Not Fire"
Start
Turn off supply and remove top cover. Turn on
and check secondary bias and reference
voltages. (Test Points 9 through 17, Table 6-3)
Voltages OK
?
Troubleshoot the appropriate
defective circuit.
No
Program voltage and current to full scale and
OV to 1/2 full scale. Check voltage at A5 J722-
22 (TP40), A1U405 and A1U602 with respect
to common (TP9).
J722-22 approx. 2.7V
?
Replace A5 DSP boardNo
A12U602-6 approx.
5V
?
Yes
A1U405-7 approx. 0V
?
Check voltage at A1U405-5 with
respect to common (TP9)
No
Yes
A1U405-5 Negative
?
Yes
Check A1U405.
Yes
Check A1R644, R747 and C417.
Voltage at A1U603-7 should be
approx. 2V.
No
Yes
Check A5 J721-12. If not 5V,
replace A5 DSP board. If 5V
check A1U602 and DSP cable.
No
Check voltage across A1R516
A1U602-6 approx. 5V
?
Check A1Q701 and CR700.
Check A1U410, Q701
(B-E short?)
Yes
Yes
No
Yes