Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old July 11th 18, 02:51 AM posted to sci.electronics.repair
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Default Realistic STA-36

I have a realistic STA-36 stereo receiver. I am trying to locate a service guide, or just a schematic. I am trying to repair the unit I have. Any help is appreciated.

Erik

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Old July 11th 18, 09:29 PM posted to sci.electronics.repair
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Default Realistic STA-36

I couldn't find a free one, maybe there's a SAMS on it.

What kind of trouble does it have ? Maybe it can be done without a schematic. Many older analog receivers are similar in design, and you can usually get the pinouts on the ICs, specs on the transistors and all that.
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Old July 21st 18, 08:31 AM posted to sci.electronics.repair
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Default Realistic STA-36

Sorry for the delay, I have a garbled sounding right audio channel, and the AM won't tune (not a huge deal)
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Old July 21st 18, 08:49 AM posted to sci.electronics.repair
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Default Realistic STA-36

I should add I know it is not the speakers I swapped the left to right and the problem followed, it is on FM, and Aux, I presume phono (dont have a player to test with) and the AM is all static, but the right channel has a low sound compared to the left.
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Old July 21st 18, 09:30 AM posted to sci.electronics.repair
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Default Realistic STA-36

What kind of equipment do you have ? Got a DVM ?


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Old July 22nd 18, 04:26 AM posted to sci.electronics.repair
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Default Realistic STA-36

I have a dvm, an analog meter, soldering iron etc.. I also have a app on my phone that can act as a signal generator, but I dont have a scope. I pretty much use it to run my ipod, or other music device through the aux, and it had been working great and sounded good until recently.

I appreciate your help by the way. Thank you.
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Old July 22nd 18, 05:04 AM posted to sci.electronics.repair
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Default Realistic STA-36

Nine times out of ten "garbled" sound in one channel when the amp doesn't fry or go into protection is because of an open driver transistor. Well maybe 8 out of 10 times.

Without a scope, the only way to test this is either static ally, which means the ohmmeter and the device not powered, or to measure the voltages in the amps while it is running, on a driver the voltage should only be a half volt or so, measuring from base to emitter. It may have forward bias (supposedly) on the base but the emitter is not there, it is more negative or positive than it should be. Except for certain circuits, like class C RF amps n ****, the emitter and base should always be within about a volt. Maybe 2, but no more. The exceptions are high speed switching transistors and that ain't what you got.

You can still get 2SC3117 and 2SC1249 at Digikey cheap and they will handle almost any amp up to about 400 WPC.

Sometimes it is the outputs, read the voltages on the bases and emitters of all of them in the output stages. Even with no signal, on3 of them is going to have more than normal voltage from B to E. Compare it with the other channel.

Anyway, try a few things and get back to us.


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