Electronics > Repair
Anritsu MS2651A repair (need service manual)
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jimon:
So finally took time to make photos of RF module, unfortunately the very first part between input (X1) and 1st LO is hidden behind a board and really hard (desoldering) to get to.

1) Photo of top of RF module
2) Close in on 1st LO-ish part
3) This is the closest thing between YiG and input ... but is it really 1st the mixer? It sure doesn't look like one :/
jimon:
4) Bottom of the RF module, looks like 2st LO is there!
5) What this thing might be ??? It was even pressed firmly by a cover, and looks like after I removed the cover (or poked into something else) I started to get 0dbm+ peak on 45 MHz instead of 0 Hz (stupid me  :palm:)
6) PLL, wonder where control frequency comes from, maybe I should poke that
7) Output board, 100 MOhm resistor O_o, but looks like it outputs 10-20 MHz signal (based on manual for MS2601A)

PS. So where the infamous mixer diodes are?
jkf1000:
Hello again Jimon, have you looked at the block diagrams in the version 1 operators manual? Have a look from around page 201 to 211 and it gives you quite a good idea of the signals you should be looking for. As a side note all the high frequency appears to be only in the 3Ghz unit, all the IF and mixer frequencies look to be a lot lower which you should be able to sniff out with a scope if you can go upto around the 100Mhz range.

If you want a simple and cheap higher frequency sniffer have you tried one of the cheap SDR dongles as a wide frequency receiver? The one I use can cover from 24Mhz to over 1.5Ghz and can make a simple spectrum analyzer with software such as SDR# but the resolution is only around 3.5Mhz bandwidth but still makes a useful tool. Karl
jkf1000:
Jimon, (or any one else that may have the same spectrum analyzer) Considering the fact that I am not able to see any information on my LCD screen, can you list in sequence the button press order to enable the composite PAL output at the rear of the analzer in the menu settings? I have read through the manual but it assumes that you can follow the onscreen prompts.  ::) Many thanks, Karl
jimon:
jfk1000, please find a video here (with instruction in the video description) :)
Not sure if this what you need, because looks like my analyzer doesn't have TV-out option (this is what it prints when I try to enable it), though it does have "composite out" on back panel. If I plug oscilloscope to "composite out" channel I'll get some signal by default without doing/pressing anything. On a board itself it marked as "Y output", and X and Z are not populated.
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