Hi everyone,
recently I decided to change all RIFA caps in my HP 3478A multimeter (I have two) as I had recently one of these caps blown up during power up.
Mistake #1: My soldering iron has tip grounded to Earth. Calibration gone. It's going to cost me $$, but I learned my lesson hard way.
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You don't have to...
Mistake #2: I wanted to clean it properly, with soft keys at front as well. The problem is when I took the front bazel off, some gold spongy boi dropped on floor. Does anyone knows what proper orientation of this gold plated sponge is? Photo would be nice.
As I wanted to send it over for calibration anyway I cleaned it and reassembled it. When I was checking voltage levels, to make sure I will sent it in mint operational condition, I noticed that -15V rail is out of spec. Like really, out of spec.
+15V rail: reading OK, +15.1V
+5V rail: reading OK, +4.99V
-15V rail: reading -24.89V
In attachment you can see where I placed probes (right on regulator leads). Is it me being dumb as shoe or is it really having issue? Does anyone else had it before?
In addition I can hear quiet clicking / buzzing noise next to rear part of mainboard and I can't pinpoint it. Any suggestions?
Regards,
No.Mad