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Hi guys !!
Suddenly I have this problem on the test set, what could it be?
I'm not going to spend a lot of money on it, can it be used with sufficient accuracy, or is it very seriously ill?
Greetings
Alessio IZ5RGO

Dear Alessio,

?? That looks like you have a bad mmic amp on the control board inside your input module. These amps supply RF to the counter. Check U4, 5 and 6. These are MSA0786 amps. Likely one is bad. Measure the voltage on them. You should see 4VDC on the output and 1.6VDC on the input.? An alternative is to just replace all 3 amps.? rick

Hi Rick,
Thank you so much again, I have check the mmic one of them U5 have some strange voltage, like 6 volts on output and 2.5 volt on the imput, MSA0786 as you know is obsolete, in a big italian supplier specilized in rf components i found a minicircuit MAR-7SM+ as exact replacement for the msa (only a noise figure is way better), if this component is good for this application, i think to change all of this amps, this chip cost only 2,30€.

I shoulda say MAR 7SM+ instead of MAR 2SM+

Hi Alessio,

? Thank YOU for the information on the MAR-2SM+ being a replacement for the MSA0786 used in the 8920 / 8924 input module counter circuit. We have a stock of the "0786" but should be using the replacement. Good luck to you ! Rick

Hi Rick,

Note that it is the MAR-7SM that is the correct replacement, not the MAR2SM.

https://www.minicircuits.com/pdfs/MAR-7SM+.pdf