Products > Test Equipment
HP 8595E spectrum analyzer repair
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MarkL:
I think the ripple looks ok.  It's never going to be perfect.  The +12V could be a little quieter, but it's not the cause of your problem.  I'd move on.  It's just good to check for anything that's wildly out of spec or oscillating.

And I'd recommend going through the procedure to backup your calibration constants (chapter 3 of the Assembly Level Repair manual), so you don't accidentally lose them while servicing.  It takes 10 minutes to write all the numbers in a chart.
kada:
Thanks all for suggestions.

I built a simple RF diode detector circuit and connect it to oscilloscope to detect RF-signals up to 10 GHz. It works perfect, I tested it with 2.4 GHz radio modules.

I decided to remove the YTO and test it RF output. And I did not see any signal. I tried to change SPAN to 0 Hz, FREQUENCY, but I did not see any signal. Also I checked +5 and +15V rail going to YTO and it is OK. Also I checked current flowing through Main coil - it was 100 mA at zero SPAN and 3.25 GHz center frequency. The FM coil current is zero.
So I guess YTO is dead. Model: HP 5086-7903. Is it any chance to repair it?
KJDS:
I rather suspect that you'll need wire bonding kit to repair the YIG, and possibly more.
AF6LJ:
Good luck, they turn up on E-Bay on ocasion.
MarkL:
I agree - it sounds like your YTO is in trouble.

Besides +5V and +15V, my schematic shows there should also be -15V on pin J3-1.  Check that too.  Check all the supply voltages at the header connector right at the YTO.  It's rare, but I've seen broken wires and bad IDC crimps on ribbon cables.

Before declaring a dead YIG, inside the can there should be a small circuit board with some individual components you could check.  Unfortunately I couldn't track down a schematic for it, but perhaps someone else has one.  I've attached a picture of it from a current ebay listing.

The 1826-1048 chip is an opamp.  You could reverse engineer the circuit a little to figure out the inputs and output enough to determine if it's working.  (Based on a very loose cross-reference search, it's possibly an OP-07).

There's also a 4-pin MOSFET and some diodes, caps, etc. to check.
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