| Electronics > Repair |
| Anritsu MS2651A repair (need service manual) |
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| jkf1000:
I have ordered a new chip for the video circuit, unfortunately none available locally so will take a few days from the USA. I no longer trust the HongKong/China marketplace for anything branded, I have had too many fakes in recent months. In the meantime I will pull the old chip and just fit a PLCC socket to make life easier. There is still the possibility that it may be one or both of the octal transceivers between the CPU and video chip so may change those as a matter of course while waiting. Jimon, I will update with any progress. and let me know if you need anything from me as far as measurements. the 12Mhz was found by scoping the back of the X2 multi connector not at the X2 coaxial connector, sorry if that caused any confusion. Karl |
| jimon:
Ok good news, AGC is f**cked after CAL procedure, so full reset (by holding preset button on power up) helps a lot! Basically SA is unusable after CAL. Some bad news, something somewhere is f**cked as well, by default I get a peak in 48 MHz when nothing is connected :/ And when I provide 100 MHz on input - I get peak at 148 MHz ... well at least mixing works somewhat, so what is it? YIG or VCO out of tune? :-BROKE |
| jkf1000:
I have no idea about the 48Mhz, I can only guess that it is a mixing product but dont have the block diagram to hand to look at the frequencies involved. It may be you have a failed filter or similar. I will look into the block diagrams and see if I can work it out for you but it does look as if you are heading in the right direction with what you have learned so far, Karl |
| khach:
--- Quote from: jimon on June 13, 2016, 09:01:03 pm ---3) This is the closest thing between YiG and input ... but is it really 1st the mixer? It sure doesn't look like one :/ --- End quote --- Yes, thats is a star mixer. IF input of mixer is RF input of analyzer. |
| jimon:
Got delivery today ... jeez I would say having the right tools for the job is a number one requirement everywhere ... so looks like X4 output (top of RF module) is coupled directly to ... I don't even know what to .. looks like unfiltered output of second mixer or something, and good news are my new epic EIP 545a is able to pick it up! Bad news are: - the screw on pic is a fine tune for resonant frequency of VCO ... I'm getting range a bit around 3.95 - 4.08 GHz - I have no idea which frequency should be there, I guess either 4110.695 MHz as specified (but the screw doesn't go that far), or 3999.995 if it's direct VCO output (4110.695 - 110.7). UPD: from X4 there is 1 strong signal around 4.0xx GHz and another one around 8.0xx GHz UPD: managed to get readings from X2 in zero span mode: cf 3ghz = 6985.03 MHz cf 100mhz = 4166.53 MHz cf 0hz = 4070.67 MHz cf -100mhz = 4008.9 MHz Sounds correct regarding the diagram (4.1 - 6.6? GHz), but I don't know if margins are ok, 6985.03 - 3000.0 = 3985.03 MHz on first IF when there is a filter for 4110.695 ... :/ |
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