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Realistic STA-2070 no display or FM

C

CouchPotato

New Member
Hello everyone, I picked up a new receiver in great cosmetic shape but not very functional.
What works: speaker controls, bass, midrange, and treble controls, stereo expander and its display are OK. Aux/TV input is working and I was able to stream some audio. The volume control, balance, power button all work fine. AM has static like it is between stations but FM has no output just a slight hum. Phono make a slight ground hum. I've taken a look at the two fuses and they are OK.

The entire Memory tuning section doesn't work so I can't really test if AM is really working or not. The whole display on the front except for the output power LEDs is out. I haven't tested the Tape functions.

I downloaded the service manual and tried to make heads or tails of this but I'm pretty new at this. Could anyone help me through some troubleshooting steps to try and get this receiver repaired?
STA-2070 outside.jpgSTA-2070 inside.jpg
Thank you,
Couchpotato.
 
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If you have the service manual, I would start by checking the power supply voltages for the parts that aren't working. The voltages should be listed in the service manual. It can be tedious to figure out where to measure these voltages, going from a schematic to the real printed circuit board, but with time and patience, you should be able to identify appropriate points. (Start with some that you know are working properly. That should help you get the hang of things.) I use mini grabbers, or a probe that I have fitted with heat shrink on all but the tiniest bit of the tip. This helps ensure you dont accidentally short something, and that you get contact with exactly the component/point you are intending to get, and ONLY the component/point you are intending to get.

If all the power supplies check out, come back and I'm sure folks will weigh in. The next step would probably be signal tracing. The service manual may or may not include a block diagram of the signal path. Again, it takes some time and patience to understand how the block diagram translates to the actual boards, but it can usually be done.

Good luck!
 
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