Sony tc654 reel repair. Only one channel works.

  • Thread starter Thread starter Steenamaroo
  • Start date Start date
Steenamaroo

Steenamaroo

...
Hi all.

I have been given a sony tc-654 to repair for a family member.
The unit works, except it does not give normal output on the right channel.

This applies to tape playback, mic input and line input.
None are audible.

The same problem is noted through line outs and headphone out.

To be truthful, i can hear the slightest trace of signal through the 'non working' output, but it's so faint that it could well just be crosstalk.

i know very little about this sort of gear, but my guess is there's a final output stage that processes audio, whether it comes from the tape, the line in or the mic in?

If this is true, i know what section of the board i'm looking at but i'm a little stuck as to what to do next.
I've put red arrows on the attached image to show where the playback heads connect to the board (one is visually obscured.)

I guess the problem is to the right of where the heads arrive at the board.

Images are at.
www.steenaudio.com/close.jpg
www.steenaudio.com/far.jpg


My first thought was the check all caps in case one is shorting to ground, but i haven't found anything yet.

Can anyone recommend a procedure for testing or speculate as to what the fault could be?


I've tested the wires that pass through the play mechanism. They are fine.
I've also checked the little I/O circuit board. I bypassed it by checking output at the wires/terminals.

Many thanks in advance,
 
I did point to point tracing with some old crappy headphones and a sine wave input.
I can trace the working channel the whole way across the board, but cannot get output from the other channel Anywhere on the board.

Perhaps this suggests a fault on one of the two 'daughter' boards? I guessed that they were for power.

I then checked the voltages at the preamplifier chips on the main board. They all check out the same.

I found a schematic. www.steenaudio.com/sony.pdf

S501 is the speed selector. Audio is getting in and out fine on both channels.
The tape/source monitor switches are fine too.


Any help would go a long way here if someone has some time.

Thanks.
 
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Maybe there was a dirty or marginal connection somewhere? Just the action of pulling the gear down was sufficient to correct it?
 
I figured out what it was.
Two resistors that are meant to be connected at one end. The connection wasn't 100%; It came and went.

Little bit of solder made it perfect! :)
 
I love it when you nail something like that! I had an intermittent problem in a Presonus BlueMax compressor that I use live. I tracked it down to a cold solder on a terminal block. Sometimes you can pinpoint these things by gently rocking the component and feeling for movement directly opposite on the solder side. Quick solder re-flow and good to go!

Paul
 
True that!

I wish it was that simple with my Akai MG.

I'm tryin to track down a fault with tape speed and not really getting too far! :(
 
Cool. I have a TC458 that worked awesome until just recently needing some TLC. It's on the list
 
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