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Old 26th Jun 2022, 10:07 pm   #1
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Default Sony TFM-1600 Fault

My sony TFM-1600 has developed a fault where it starts to crackle after being on for a while, Kinda sounds like silver mica disease. But would have thought that it's a bit too modern to be suffering from that. Iv'e cleaned all the controls so don't think it's an issue with them.

Any ideas ?


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Old 5th Jul 2022, 6:00 pm   #2
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Default Re: Sony TFM-1600 Fault

Bump,

Anybody got a clue what the problem might be before it hits the bin ?
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Old 5th Jul 2022, 6:09 pm   #3
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Default Re: Sony TFM-1600 Fault

Could be a failing transistor, I had a similar fault on a Panasonic set of around the same age.


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Old 5th Jul 2022, 6:14 pm   #4
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Default Re: Sony TFM-1600 Fault

Quote:
Originally Posted by mark pirate View Post
Could be a failing transistor, I had a similar fault on a Panasonic set of around the same age.


Mark
Cheers for the reply mark, Yeah it could be but finding it is the problem,


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Old 5th Jul 2022, 6:25 pm   #5
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Default Re: Sony TFM-1600 Fault

I usually find freezer spray very useful with suspect transistors, especially if the fault occurs after the set has been switched on a while.

I have also found random crackling can be down to noisy resistors, but my money is on a faulty transistor.


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Old 5th Jul 2022, 6:56 pm   #6
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Default Re: Sony TFM-1600 Fault

That's what i was thinking mark, I presume the faulty component must be in the AM Section of the radio as it seems to work fine on FM, Its the most sensitive radio iv'e ever seen and when its working it sounds great so worth saving if possible.
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Old 5th Jul 2022, 8:18 pm   #7
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Default Re: Sony TFM-1600 Fault

Certainly worth the effort of tracking down the fault, the first thing is to find the circuit diagram, it will be a great help in narrowing down where the fault lies.

It obviously is somewhere in the AM circuitry, as FM is fine, it also rules out the output stage.


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Old 5th Jul 2022, 9:39 pm   #8
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Default Re: Sony TFM-1600 Fault

When the fault occurs, it might be worth gently tapping the various trimmer caps with the blunt end of a screwdriver. If any of these are breaking down then this would soon show with the crackling.
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Old 12th Jul 2022, 7:21 pm   #9
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Default Re: Sony TFM-1600 Fault

Think i might have fixed it, After probing the board i noticed i got a loud crackle every time i touched the FM portion of the band switch, Cleaned the band switch and it's been fine for the past two days.

Why bad contacts in the FM Part of the band switch were causing a loud crackle on the AM bands i'm not sure.,

But so far so good.
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Old 12th Jul 2022, 9:03 pm   #10
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Default Re: Sony TFM-1600 Fault

Wonderful. Is suppose the FM part of the switch probably switches power to the AM front end, so bad contacts would cause intermittent operation.
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Old 23rd Jul 2022, 12:58 pm   #11
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Default Re: Sony TFM-1600 Fault

Have another slight problem with this radio and that is receive drops off on MW when i go below 650 Khz, Above 650 Khz it's very lively.

I'm thinking a weak oscillator transistor, Unfortunately i don't have a schematic for the radio.
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