Precision II Operation and Maintenance Manual C
5-8
996-0255 rev. b
time you press the RB601 FIRE button. If no signal is
present, repair CU601C.
6) Look for PU FIRE signal - On rear of PU use BNC “T” to
measure the signal going from PU J5 to CB J5. The signal
should go from 24 to 0Vdc each time the RB601 FIRE
button is pressed. If the signal is there:
a. replace lamps in laser head
b. repair suspect CB
If signal is not present, repair PU.
B. Q-switch troubleshooting
The following is an electrical test procedure that allows for determination
of defective Q-switching electrical elements. Those elements are:
• CU601C
• Marx board
• 750 power board.
Equipment needed:
• oscilloscope
• standard scope probe
• DVM
• long (~15' ) BNC
• BNC “T”
• pot “tweaker”
1) External trigger your scope on the 24 Vdc to 0V signal
coming from the “J4” BNC connector (use BNC “T”)
located on back of oscillator capacitor bank. This 24 V to
0V signal occurs at start of flashlamp firing.
2) On your oscilloscope set the following:
Termination - 1 MΩ
Time base - 100 µs/div
Vertical amp - 5 V/div
Trig - external and negative going.
Scope trace should be placed near top of screen.
3) Place the standard scope probe between the two connec-
tor pins extending from the top of the Pockels cell. The
probe should lean against the two contact pins but MUST
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