Or, just flaky relay contacts on the 2 most used channels...
I encountered similar issues in the past with HP 54100-series attenuator modules. In most cases, it was caused by dirt or dust finding its way into the relay mechanisms, accumulating over time and and hindering the actuator. Most of them were fixed by soaking in IPA (using a syringe to spray it in), actuating it while wet, rinsing with IPA, and repeating if necessary. Use a vacuum to suck out the excess IPA and let dry completely before testing. I'd guess I had 75% success rate doing this.
I am so sorry but what do you mean with "IPA" ? IsoPropyl Alcohol?
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I used Kontakt 60 applied to a tooth pick (wood) and cleaned the springs and posts with that, then washed down with Kontakt WL.
But strangely CH2 did not get any better, in fact it only became worse. Now CH2 is totally whacko. At low mV/div settings there is only a few LSB of signal appearing (while input was 2Vpp) at 5V/div this looked more like 15Vpp, in middle ranges (eg. 200mV/div) I got nothing on screen.
I pulled out the attenuator again and checked each relay contact, in both states, and it works fine! No other sign of failure.
So I put in my newly acquired spare attenuator and with this it works good, only that it reads some 10% lower voltage than it should, I guess I have to recalibrate that channel? If so how to do that?
I encountered similar issues in the past with HP 54100-series attenuator modules. In most cases, it was caused by dirt or dust finding its way into the relay mechanisms, accumulating over time and and hindering the actuator. Most of them were fixed by soaking in IPA (using a syringe to spray it in), actuating it while wet, rinsing with IPA, and repeating if necessary. Use a vacuum to suck out the excess IPA and let dry completely before testing. I'd guess I had 75% success rate doing this.
As you said you fixed this issue by soaking in IPA the relays and then actuating it while wet.
How did you activated the relays while they were wet? Did you do this with the attenuator module out of the oscilloscope (I guess) ?
Thank you very much.
Yes, with the 54100's you can remove the input module fairly easily. And the relays can be actuated manually too, all of the actuating levers are accessible with a small screwdriver.
I'm sorry, but I'm out of suggestions, Jaime. Maybe someone else has some experience with them?
Putting the magnet in the wrong place should be no problem, as once you step through all the ranges they should find their place. In my case I found that some relays were harder to move than others, thosey may stuck "inbetween" places causing unusual errors.