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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 1st Mar 2018, 6:52 pm   #1
Rohit123
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Location: Bangalore, India
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Default Akai GX4000D - Left Channel Repair

Hello Everyone,

I just purchased a second hand Akai GX4000D tape deck. Unfortunately the left channel is not working. It only works on the playback mode with pre-recorded tapes.

When I engage the Monitor to SOURCE and send an input signal, I get the output from the right channel. However if I crank up the signal from my computer/cassette player, I get a very inaudible sound from the left channel. When I use MIC as an input, the left channel shows the same symptoms.

When I engage the SOS function with MONITOR on TAPE, I get output from both channels.

A little background, I have used deoxit d5 on all pots and switches with no result. The tape path is super clean. The cables used are all working. Have changed all the fuses. The tape used is brand new. But till no luck.

This brings me to my question.

What should I do? Where should I begin. Is it the transistors? If yes, which ones could they be? And, what are the replacements? here is the service manual -

https://www.hifiengine.com/manual_li...gx-4000d.shtml

I don't really know how to read the circuit diagram and learning to do so.

Has anyone faced a similar problem?

Any little help will mean a lot to me as am doing this for my mother. Am from India and any guidance regarding vintage machines is very hard to come by.

Looking forward to bringing this beautiful machine to life. Coz there is no school like old school. \m/

Warm Regards,
Rohit
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Old 8th Mar 2018, 8:56 am   #2
Michael Maurice
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Default Re: Akai GX4000D - Left Channel Repair

Hello Rohit,

I've only just noticed this because it was posted in the wrong section. Its been moved now.

Do you have a multimeter and test meter? If so I would start taking voltage measurements around TR3 and TR4.

Please let us know how you get on.
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Old 10th Mar 2018, 3:13 am   #3
WreckTangle
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Join Date: May 2014
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Default Re: Akai GX4000D - Left Channel Repair

A common cause of problems in these Akai decks is failure of the 2sc458 transistors. Look carefully for telltale black oxidisation on their legs. Even better if you are able to reconcile ones that have this oxidisation with their position in the left input channel on your circuit diagram.

You may find all the transistors have evidence of black leg syndrome. They only fail when the black rust gets into the can.

I used 2SC2240 as a replacement when I got my Akai out of storage and both channels had failed. I found it was just about possible to replace them without removing the circuit board, which I think is quite involved.
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