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81150A Repair /  DAC output network

Question asked by bonf72 on Apr 24, 2018

Hi all,

I have a 81150A function generator which was in a rack where another instrument caught fire. After cleaning it works fine, but it failed calibration due to output noise.

When I checked the signal path I found that there are components in the DAC output filter that seem to be broken. I can measure neither resistance nor capacitance, so I assume they were damaged in the heat.

81150A DAC output network

Is there any way to find out what component belongs here? When I take them out I can't measure anything, so they are <0.5pF and >100MOhm.

At least in some places there where two soldered on top of each other. The data sheet of the DAC does not help either, because they assume an AC output using BALUNs and capacitors.

Also the two outputs seem to have slightly different components - could they be matched to the DAC? Or did I accidently remove a component while cleaning?

Hope somebody can help.