Electronics > Repair
Anritsu MS2651A repair (need service manual)
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jkf1000:
Thanks for checking that for me. exactly the signals I expected to see if measured from pin 13 and 14. ( On a working machine ) Time for me to order a new chip as I have no regular pulses on my unit so no timing control for later stages. The other possibility with mine is corrupted data from the CPU or bad 3 state transceivers between the CPU and the ACRTC chip. I am flying a little blind on this without data so its a process of elimination based on best guess and logical signal paths. I will report back with any progress but it may take a while to source the parts.

I just hope that if or when I restore my display there are no further issues with my machine lol.

Did you check your backup battery and run a full calibration sequence with your machine as I suggested earlier? It may give you more of a direction to go in if it does not resolve your level problem. If I can return the favour with measurements from my unit let me know and report back with any findings and progress you make. Karl.
jkf1000:
I will check the IF for you but it wont be until tomorrow evening at the earliest. Please bear in mind also that until my display issue is resolved I cannot determine that my machine is working 100% Karl
jimon:
Self cal doesn't do much, either mixers are completely dead or either something is really strange.

Basically my current situation is just crazy:
- Did "All Cal", it went fine. And actually I've checked what happens if you just remove cal input from main attenuator - the device doesn't care, there is simply no "calibration failed" errors (or I was not able to trigger them any way possible)  |O
- Did preset -> All, and I'm getting straight line over 0 dBm on whole spectrum
- Device reports >+4 dBm (sometimes +300 dBm) over all spectrum
- If I provide some input signal, spectrum around this signal jumps down to ~-50 dBm
- Noise level (can you really even say +4 dBm is a noise level???) jumps between different levels when I switch between different RBW.
- Backup battery is doing fine, minor level of oxidation is present though.

Not having tools to properly test 1st and 2nd mixers (I don't even understand wiring of them) makes me sad :palm: For now I just want to know what works and what doesn't.
jkf1000:
Study and try and understand the block diagrams in the manual. They are our only source of information at the moment. Assuming that my unit is functioning 100% as far as the RF stages is concerned, between both our units we should be able to resolve both units as both appear to have completely unrelated faults. Karl
jkf1000:
One other thing you can try is to hold in the Preset button for 5 to 10 seconds while powering up which boots the unit into a default condition according to the manual. Karl.
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