Capacitor plague? Inside an HP 8620C sweep oscillator and HP 86245A RF plugin


A teardown of the HP 8620C and HP 86245A by Kerry Wong:

I just picked up an HP 8620C sweep oscillator with an HP 86245A 5.9 GHz to 12.4 GHz RF plugin on eBay. This time around though, the unit does not work. While it was advertised as a working unit I could not get it powered on and there was no sign of life whatsoever. So before I start troubleshooting and repairing the unit, I thought I would do a quick teardown to see what’s inside and if I could spot anything obvious that was out of the ordinary.

More details on his blog here.

Check out the video after the break.

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1 Comment

  1. I think no plague. Both failed capacitors are on the same side. Look at the backplane, it’s likely the failed caps were on the left side, next to what looks like the power supply section. For old equipment, there is usually a big-ass transformer somewhere there. The temps were probably fine for say a 5 year design life, but even very good caps may fail say by 10 years. These are old axial caps, the seals will harden and some leakage or evaporation of electrolyte will occur. Not surprisingly we then have wire corrosion leading to failure. I think the parts are fine, it’s just they are well past their design lifetime (which is dependent on temperature etc).

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