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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 17th Jan 2023, 6:39 pm   #1
IanNVJ35
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Default Sony Microcassette M330 overheating

I am having a go at fixing this little machine for an older lady who wishes to play her old micro-cassette collection.

I somehow feel it's a bit beyond me as it's all surface mount and no manual but I have the fault of seemingly no operation, so I tried on my bench PSU. I see that the Voltage (3) is dragged down to around 2 at 500mA limit with the power amp IC getting hot.

Nothing operates nor does the motor turn.

It's this one. https://www.nisshinbo-microdevices.c.../NJM2073_E.pdf

I checked if it was short internally - it isn't. I checked if the output was shorted - again, it isn't. There was some heavy brown flux on the trace side of the PCB around many of the solder joints which I cleaned off leaving an odd remnant of white gummy stains. I'm wondering if components may have been damaged by this.

Thanks for any ideas. If I can't fix it I will just return to her but I want to try.
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Old 21st Jan 2023, 12:42 am   #2
ben
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Default Re: Sony Microcassette M330 overheating

The problem is likely very near the power input. Short in a dc socket? Probably simpler to pick up another one online, they're cheap enough.
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Old 21st Jan 2023, 12:02 pm   #3
knobtwiddler
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Default Re: Sony Microcassette M330 overheating

Does it contain tants or types of caps that can fail short circuit?

MLCCs, especially SMT types, can fail this way.
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Old 21st Jan 2023, 12:26 pm   #4
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Default Re: Sony Microcassette M330 overheating

I have the paper service manual for this model that I could scan and email to you. If it's of any help PM me with your email and I'll get it scanned in the next couple of days.

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Old 21st Jan 2023, 1:10 pm   #5
IanNVJ35
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Default Re: Sony Microcassette M330 overheating

Thanks for the input. I checked for tants but only a few electrolytic ones which read OK.

I'm actually running from the battery supply with flying leads. This evening I will lift the DC input leg on the amp - see if that helps.

Dave, the service manual would be appreciated. I'll pm you.

Yes I thought straight away of suggesting a working replacement but I'd at least like to try. I'm interested in what could be wrong.
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