Hi!, i dont know if here is the right place to post, but any help would be very appreciated. I got a Technics SA-GX190 "Control Stereo Receiver" all in one with dual stereo amp, a friend gave me to fix it, aestethically is looking pretty good, functionally...well... sometimes works and sometimes doesnt, i managed to get everything working again, found bad relays, many cold solders..etc, except the receiver part... when you turn on sometimes you don't get any station on all bands FM/AM/MW but when you turn off it few times again i can get it working back.
Here are the symptoms in a more detailed view:
- noise after dialing stations when it was working, sometimes no sound at all
- noise after disconnecting and putting back the antenna
- silence after putting my hand close to the circuit board, probably because of interference
- the noise sometimes varies on volume, and after some time the stations
come back with a fading effect
The receiver circuit is a modular board
My guess is a faulty PLL, it uses a synthetizer chip for dialing the stations commanded by a microcontroller on the front panel, because sometimes the stations are innacurate/wrong despite what shows on the front panel
fortunatelly i found a schematic of the SA-GX170 model which is identical i'll post here
any help would be really appreciated since my friend will pay me good if i get it fully working 😀... thanks in advance
Here are the symptoms in a more detailed view:
- noise after dialing stations when it was working, sometimes no sound at all
- noise after disconnecting and putting back the antenna
- silence after putting my hand close to the circuit board, probably because of interference
- the noise sometimes varies on volume, and after some time the stations
come back with a fading effect
The receiver circuit is a modular board
My guess is a faulty PLL, it uses a synthetizer chip for dialing the stations commanded by a microcontroller on the front panel, because sometimes the stations are innacurate/wrong despite what shows on the front panel
fortunatelly i found a schematic of the SA-GX170 model which is identical i'll post here
any help would be really appreciated since my friend will pay me good if i get it fully working 😀... thanks in advance
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Troubleshoot the power supply first - noting voltages against the schematic.
Make sure any and all regulators are within voltage ranges.
In the tuner block, and on that board, determine if any capacitors are suspect.
I'd likely find the issue if it was on my service bench, but across the world is a different story.
I'm "old school", I don't like to speculate like others seem to do.
Make sure any and all regulators are within voltage ranges.
In the tuner block, and on that board, determine if any capacitors are suspect.
I'd likely find the issue if it was on my service bench, but across the world is a different story.
I'm "old school", I don't like to speculate like others seem to do.
hello, thank you for the reply.. i found the issue, it was a bad solder i forgot, on the connector of the receiver board, due to the symptoms i thought it was something complex but fortunatelly it wasnt