Akai GX-635D sound issues

[Soundbyte]

Hello all,

My Akai GX-635D has been in its box since about 1993 along with a bunch of other great stuff like my Kenwood Eleven GX. I pulled everything out and set it all up, but was so disappointed to find that the right channel on the 635D reel to reel was dead. I've been doing alot of reading and hoping to see if I can narrow down the problem and what the cost would be to repair it.

*Left Channel working, Right channel has no sound and no meter movement.

*Took leads from head block to amplifer board and switch them - still no sound to right channel but sound was backwards in the left.

*Held back tension arms and removed reels. Pushed play - both channels sounded the same, no sound at low volume and white noise as volume increased.

*Attached RCA leads from my cassette desk to the back input and pushed Tape/Souce button. Same thing, sound in the left channel but right channel is dead.

[HeadGap]

I just joined TH this morning and I have a Teac A-4300 R2R that I had to fix a dead channel problem with and as I recoll it was a bad capacitor. Caps are kinda like batteries and are as likely if not more likely to go bad just sitting on the shelf or box being ignored and hardly ever getting charged.
Mine was I think a Mylar coupling cap that sends the sound signal from one part of a circuit to another.
Your problem nay be something entirely different but I would definitely suspect a cap or switch. Switches are probably what I half to overhaul the most, especially in 2 head cassette decks as they share the same head for record & play and therefore a lot of switching of circuitry happens between the 2 functions. Your 3 head R2R shouldn’t have that many switches. The nice thing is you have one good working channel to compare against the bad one and even without a schematic diagram it’s not to hard to follow the signal path for each channel. I used an oscilloscope for this, but I’m thinking if you have or bought/borrowed a fairly good DMM (Digital (I know, bad word) Multimeter that could read AC voltage in the Millivolt range you could maybe follow the signal from a tape you know has sound on both channels in play mode and compare what you have on each channel and see where the signal stops in the bad channel and continues on the good channel. The black or negative lead of the meter can just be clipped to chassis ground. If you have a good deck to play tapes on you might do a recording on the bad deck and play it on the good deck to see if the record function is working OK.
Sorry, this is pretty long but it may help some, just always be aware that there is 115 volts AC around that power supply and I’ve gotten across that stuff before and it’s no fun so always be aware if the deck is plugged in end turned on or not. The big AC should all be around the power supply area and off on switch and you shouldn’t have to worry about any of that in the amp circuits, shouldn’t be to tough with a big ol R2R unit, lots of room to work.

Hope this helps

[Soundbyte]

Yep, I have been doing alot of reading and I figured it was the caps. I rememeber in the early 80's having some work done when I was in Omaha. I think I still have the part they replaced in a bag somewhere. I've got a good voltage meter, I just have to make time for it. Not too good with solder on the board level. Might have to find someone in the KC area. Any idea what it will cost?

[HeadGap]

I really don't have a clue what shops charge for something like that. I wouldn't think it would take an expierenced tech long to find the problem so I would think maybe 75 dollars or so.
A friend of mine has/had maybe a 630 or something and I got a chance to use it years ago and I thought it was such a cool machine.
Good luck with yours, I hope you get it fixed.

[studeb]

Hi,

So from what you have said there is no sound from the heads in the left channel, and there is no sound out from the input at the back. Swapping the head leads gave sound out the right, so the head is likely okay

The playback amp has two sections, one does the initial gain and eq, then a second for the output and meters. The problem is at a minimum un the second amp section, as the tape input is amplified there. There is a 2sc458 (Tr9) in that amp, and they are known to fail. You could replace that with a 2sc2240 to see if that fixes the problem. i would replace the other 2sc458 in the amp sections as well all the caps in the amp and the power supply at the same time.
If you do not want to do it, a shop can do all that. Could be $200, i really don't know, i do my work myself.

At any rate, its not terminal, good luck

[Soundbyte]

Ouch, sounds like a lot for labor. "My dad's a TV repair man and has an awesome set of tools... I can fix it." (Great movie line that just seems to fit here). Actually, I do have a pretty nice Weller solder station so I just may have to check ebay out for the caps. Thanks for the info!

[toddbailey]

Ouch, sounds like a lot for labor. "My dad's a TV repair man and has an awesome set of tools... I can fix it." (Great movie line that just seems to fit here). Actually, I do have a pretty nice Weller solder station so I just may have to check ebay out for the caps. Thanks for the info!


Don't buy caps off ebay go to allied, digi-key, mousser, parts express or any other parts distributor.