Author Topic: HP 3585B calibration error message  (Read 274 times)

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Offline gimble88

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HP 3585B calibration error message
« on: May 04, 2021, 12:06:54 am »
My HP 3585B is showing the error code "calibration error 17" when first powered up. This error comes up every time the unit automatically does a calibration. However, after it's been on for a while, the error stops occurring and calibrations go as normal. Once the unit stops throwing the error it never show up again until it's been off for a while.

The length time it has to be on before the error stops occurring varies with how much it has recently been used.
It can take anywhere from a few minutes to a few hours.

The manual is very vague about this error, saying it is on one of two circuit boards. These boards are large. I am using a GPS disciplined crystal oscillator for the frequency ref so I know it's not an issue with the oven controlled internal oscillator.

My wild ass guess is that it could be an electrolytic cap. My reasoning (ha!) is that very few parts get better over time and then don't cause any trouble until the device is powered down for some period. This seems like the behavior of an electrolytic cap that has failed and is being reformed when voltage is applied.  I'm leaning away from a PS problem since the device works perfectly in all respects, all the time, except for the calibration after startup.

There are of course a ton of resistors, caps, discreet devices and IC's. In my experience resistors don't heal, nor do discreet semiconductors. I aware that IC's can do weird things but the fact that after the device has been on for a period and stops showing the error, it never occurs again no matter how long it remains on makes me doubt that an IC is the problem. I know it's a common trouble shooting
technique to apply freeze spray to individual components to see if that will show the failing component. But, I don't have any extender cards for these circuit boards and though I may have to make some,
the connectors aren't easy to source. It's a 1980s machine.

So I'm thinking of shotgunning all the PS decoupling caps on the two boards as a start. My experience with trouble shooting is mostly in analog circuits and mostly under
200kHz, though I do dabble in sub GHz RF.

I love this machine and it perfectly suits my needs. So I'm wondering what ideas anyone might have.

Thanks,
Spence

 

Offline gimble88

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Re: HP 3585B calibration error message
« Reply #1 on: June 06, 2021, 05:18:14 pm »
I thought I would bump this up one more time in hopes that someone might have some insight into this failure mode. Thanks.
 

Offline gimble88

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  • Country: us
Re: HP 3585B calibration error message
« Reply #2 on: June 16, 2021, 08:21:02 pm »
I am posting this so that some information will be available if someone searches a similar problem. I have cured this calibration error problem with an end run. First I looked at the three IF cards and they have only a couple of electrolytic caps each. I checked them with my LCR meter and they were on spec with low ESR. So probably not a cap issue. In addition there are about a hundred teeny tantalum caps on each of the cards which I would be loath to test and replace and it's my understanding that the failure mode for tantalum caps doesn't match my symptoms. My next suspect was going to be the IF crystals, two to each board. But now I won't have to go there

The solution: I happen to have an HP 3585A version that I set aside when I found this 3585B that is acting up. Since I believe the only changes are in the digital realm (like more memory registers more flexible and complete peak finding etc.) I realized the IF cards from the A version could be swapped in. They have the same part numbers and, in fact, after swapping them in the problem is totally gone and the 3585B is working perfectly. I can't even find a reason to mess with calibration. Looking at some spectra with the original cards and the A cards the differences are less than 0.5dB.

This means if cards from the analog sections of one of these are faulty it will be much easier to source replacements. As near as I can tell the installed base of the A version is probably about 5 times that of the B version.
 


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