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8595E repair

Question asked by kada1 on Sep 6, 2015
Latest reply on Sep 8, 2015 by PA0ALV
I bought a nonworking 8595E analyzer. The analyzer did not turn on. I was able to repair the power supply. When I inserted the repaired PSU to analyzer the -15V LED turns off and -15V disappear.

The problem was in the burned shorted tantalum capacitor located on the Narrow Band IF Board which was replaced: IMG 2048

After it I can power on the analyzer but other problems were revealed:

1. Very slow reaction to controls and display refresh - need to wait 10-15 seconds after each key presses. And spectrum refreshes once every ~30 seconds. Empirically I found out that if disconnect the A25 Counter Lock board the problem is resolved. The board is defective?

2. No response of analyzer to 300 MHz calibration signal. The calibration signal level and frequency was checked using frequency meter and millivoltmeter. It corresponds to 300 MHz -20 dBm. If I try to do FREQ CAL the error will appear: CAL SOURCE NOT FOUND.

I measured the signal with millivoltmeter at the point A (after Attenuator -> YTF -> LPF) in the band 0 and it seems good. So I guess the problem may be in the Dual mixer or Second converter. But I have not instrument to check the high frequency signal after mixer.

How I can to localize the defective part? I have not RF generator or other analyzer. I have only 15 MHz generator and 100 MHz DSO.

Analyzer screen after power on (A25 Counter Lock board connected): IMG 2050

After 10 seconds: IMG 2052

Thank you all who responded.  

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