Hi Stan,
It gets like a broken record, but the first place I always go when a
formerly working piece of test equipment stops working is the power
supply.
Check the power supply voltages for both value, and ripple.
Then check all of the electrolytic capacitors for ESR. It only takes
one, in a loop somewhere, that has opened up to completely hose the operation.
Tantalums are notorious for becoming short circuit... Fortunately, HP never
really endorsed the epoxy dipped tantalums, like Tektronix did. However, the
milspec axial leaded caps they did use sometimes open circuit.
The 5065 is loaded with carbon composition resistors (IIRC). They are noted
for drifting out of range... particularly the high value resistors.
The very last place to go is any adjustments!
-Chuck Harris
OBTW, I would be able to help you more, but Scott McGrath borrowed my manual
for scanning, never finished scanning the schematics, and seems to be intent
on keeping it. I hope he proves me wrong, and does the right thing.
Stan wrote:
I have a "late model" (s/n 2816A01565) 5065A that had been running fine for
quite a while in my lab at home. About two years ago I had to power it down
and store it away in climate-controlled storage during a remodeling project.
Last night I got it back out of storage and powered it up. Initially, after
the ovens had warmed up I was able to get it to lock, but by this morning it
had unlocked. I noticed that the 2nd harmonic, which last night had been
reading close to its historical value of 30 on the meter, now read 0.
Opening the loop for a few seconds and then closing it made the 2nd harmonic
reading go back up to 30 for two or three seconds and I was able to get the
continuous operating light to come on, but then the 2nd harmonic drifted
back down to 0 and the green light went out.
I have the O&S manual, but it's still in storage. Since, it's been a while
since I played with this instrument, I'm wondering if someone can tell me
what's going on, where I should start looking, and what, if anything, I can
do to correct the problem.
Thanks,
Stan
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