Re: 8590B low sensitivity problem...
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I probably don't know what I'm talking about, but...? I had similar
symptoms with my Tektronix 494AP, where it would not complete the sorta
self calibrate.? Turned out the sensitivity was about 20 dB
low.? I tracked this down to one of the input attenuators being
stuck.? Cleaning the linkage cleared the problem and he now works
fine.
I don't know the architecture of the 8590 series of analyzers, but I think my first test would be to by pass the input step attenuator and see how the sensitivity is going in after the attenuator; at least to rule that out as a possible problem. Burt, K6OQK 8590B low sensitivity problem From: Martin Whybrow Date: Fri, 04 Dec 2020 07:30:46 PST Having repaired the PSU and overcome my issue with corrupt NVRAM, I'm now trying to run the self calibration routines. The frequency routines run OK, but the amplitude routines fail very quickly. Testing the analyser with a variety of sources shows that it's very insensitive, unable to discriminate a signal below about 10MHz, improving very slightly as the frequency inceases to 200MHz, but still 70dB too low. I'm having to use the 8590E manual for the fault finding process as I'm unable to locate the service manual for the B; I do have the CLIP for the B version, although there do seem to be differences on my unit, e.g. the backup battery is on the main board and is AA rather than the A123 battery on the memory board indicated in the CLIP. The service manual calls for the HP IF Test Module which isn't something I can lay my hands on, making it rather tricky to fault find signal level issues, especially as the CLIP doesn't have signal levels marked in many places. Does anyone have the correct service manual for the 8590B or can tell me what signal levels to expect at various locations?
Burt I. Weiner Associates |
Burt K6OQK