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I have wanted a spectrum analyser for years and then I find one in the skip
Its an Aeroflex IFR A7550 spectrum analyser with tracking generator. Specs here. It seems to be in decent condition and all controls still feel good so I’m hoping its just the power supply that has died.
It powers up for a split second then proceeds with a nasty squealing sound. This is an intermittent fault and will power up successfully most of the time. I suspect either leaky caps on the PSU output or one of the modules is drawing too much power.
If someone knows how i can get hold of a service manual, please get in touch.
Update (13/12/12): Ok, it seems the power supply cannot deal with the initial inrush of current to power the display. I can now use this fine by connecting my bench supply when I turn it on. The bench supply can then be removed and the internal PSU continues to power the whole thing no problem.
Update (17/11/12): Just got hold of a few original diagrams for the A7550 PSU circuit and assembly. Enjoy it here: A7550 PSU circuit diagram
Update (4/08/12): The squealing fault progressively got worse and now will not power up. This makes me think it could be a leaky capacitor in the power supply (hopefully). If anyone has experience with servicing these or can help me fault-find the SMPSU then gimmie a shout!
I’ve wanted one of these for years and then i find one in the skip! This thing is really well made and very heavy. This must have cost a fortune in the 80s
Very tightly packed. A nightmare to get to the bits in the middle
The first thing i checked was the power supply. All seemed to be ok. No leaky caps or dead diodes like i suspected there would be. Edit (4/08/2012): i’m not convinced all the caps are healthy! i’m gonna dive back in soon.
Open power supply
yesss! this has the 10.7Mhz receiver module in. Great stuff, i should be able to listen to radio broadcasts through the built in speaker
I went a little deeper. Its Sunday after all
CRT and RF modules out
I hate this high voltage stuff but i was drawn towards this strange looking, half melted component with 6 legs (see below). What is this?
This is on the CRT board which is a Computron 115DMX. I was convinced for a while that this may be causing a short but after testing it, it seemed fine… by fine i mean no shorts, which was kind of what i was looking for at this point
Computron 115DMX CRT board
So after hours of desoldering/soldering, checking suspicious looking diodes and caps i get it to turn on for the first time!
Brilliant. This looks great compared to my Chinese Atten spectrum analyser although its probably due for calibration but i’ll leave that for another Sunday. I gave it a whirl and was pleasantly surprised to hear demodulated FM coming out the internal speaker. Its a great feature. I made a video of it here