Products > Test Equipment
HP5385A OCXO Timebase
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Miti:
Sorry I missed all these requests for boards. I don’t have any board left.
pizzigri:
Hello Miti,
I am building the board, however there are a few things that are unclear to me in actually mounting the OCXO on the meter.
First off, the jumper you refer to are W2 and W3, correct? Meaning I remove the 0R part from W2 and solder it to W3 to switch to oven XO.
Plus, I removed the original TCXO, added the ferrite inductor and I have a 70nf ceramic disc capacitor salvaged from old equipment (forgot to order it in the Mouser BOM... crap), would that be OK?
Do I need to do other things to make the transition?
Also, I can not find replacements for the three big caps in the power section, especially the big ones as they have three leads.... any suggestions? It’s not that they don’t work, but the smaller one is suspicious and since the meter is open on the bench I thought to recap it.
Miti:
That sounds right to me. I did not recap my counter, it may not be necessary.
pizzigri:
Ok, so to update this thread with a happy ending....
I built the board and installed it. The OCXO I bought from Ebay continued drifting for almost two weeks, I actually thought it was defective. However, in the end it settled and I managed to calibrate it against the GPSDO to a couple millihertz. Extremely difficult to since the freaking OCXO can feel the heat coming off my hand when I get near to it. The Morion MV85 I have is not so critical. Mah? In any case, once done it’s over a week Miti’s board is stable and not drifts at all. I am enclosing a couple pictures, the first one is at turn on of the meter, the second one is after 20 minutes and is spot on. I am grateful for Miti for the project and help in building it and also to every one of the EEV Blog members that also helped and posted in this thread. The HP 5385A is a fantastic counter, no fancy stuff but a basic solid meter that just works and has great resolution, I mean there aren’t all that many 11 digit counters around at less than 200$, granted not on all ranges....
pizzigri:
So, since people have asked...
Miti's OCXO board is a direct replacement for Option 004 Oven Timebase, mfr 28480, code 0960-0636.
And, is therefore compatible with the following HP meters:

5384A
5385A
5386A


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