Author Topic: A hopefully not to sick HP 3585B.  (Read 475 times)

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Offline Zenwizard

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A hopefully not to sick HP 3585B.
« on: September 03, 2019, 11:43:45 pm »
I have a HP 3585B on the bench that is in immaculate condition. And from preliminary testing everything seems to be working except for one small hiccup. When I turn it on it is failing calibration 02 during warm up. And after leaving it on for a while for a weird reason the crystal oven is not powered on all the time in this one. it keeps saying error 2 if you power cycle it hot it goes in to a LO unlock state and will not lock the LO. I have hooked the oven up to a scope and I am getting a nice sign wave out. My frequency counter says the oven is off by 1 Hz in 10 Mhz. I have fixed a few scopes but a spectrum analyzer is in another league. Not sure where to start on this one.
 

Offline wn1fju

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Re: A hopefully not to sick HP 3585B.
« Reply #1 on: September 04, 2019, 01:01:31 pm »
You do have the jumper cable on the back panel from the oven ref out to the external reference in?

Download both the operation and service manual from Keysight's web page.  It's a bit tedious, but you can march through the debug procedures.

Sometimes, due to age, the internal oscillator drifts out of adjustment and can't lock to the external reference.  Tweaking the adjustments often helps.  You could try and see if this is the problem if you use a good signal generator (with 1 Hz resolution) at 10 MHz as the reference and adjust it a few Hz up or down.

 

Offline Zenwizard

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Re: A hopefully not to sick HP 3585B.
« Reply #2 on: September 19, 2019, 03:02:09 am »
Seems this was a noise issue on the input for the reference oven. The cable got pinched between the board and the top of the case. I got it moved and cleaned some slightly tarnished board pins and the LO unlocked is gone. Let the unit run for a few hours to get good and hot and it did not through a single error so it looks like all is good.
 


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