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Another Akai GX-635D thread!

djtchort

djtchort

New Member
Hello everyone,

I’ve read every GX-635D thread here already and attempted some things.

So I have a GX-635D with barely any output. I have to turn it all the way up and get my amp all the way up just to hear anything. Same with headphones out. So, I went ahead and replaced all 20 2SC458’s on the amp board with KSC1945FTA, but there is no improvement. So, I guess I need to replace some caps now?

Here is weird part. While testing, I decided to hookup a tape deck and see if input working. Nope, same barely audible sound, HOWEVER, when Tape deck OUT connected to GX-635D OUT and headphones are plugged into Akai, I hear output of the tape deck in headphones and not only hear, I can control volume on the Akai and even VU meters on Akai move. Barely noticeable, but they move! Volume is pretty nice and loud. And if I press Monitor/Source button on the Akai, Volume works as well, but it’s loudest in the middle and all the way up its quiet.

What is going on here??? Is something shorted?
 
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I am confused by the "Testing" you detailed-but feeding signal into the output would yield weird results, I would think.

Have you confirmed the tape plays on another deck?
Have you cleaned the heads thoroughly?
Have you cleaned and exercised the source\monitor switch thoroughly?
Same for the output level pot-clean and exercise thoroughly.
I can't recall what the deck uses to switch record and play signals-it's either relays, or a slider switch actuated by a solenoid. Contacts in these can also impede signal. Confirm that the tape is good, and clean, before you try to deal with rec\play relays or switches.
 
These are good decks but famous for having lots of “**** house” transistors that should be replaced.

REPAIRING THE DREADED AKAI GX-635D TRANSISTOR ISSUE....

Ok guys, I finally got around to fixing one of my Akai GX-635D reel to reels. It had NO playback at all on either channel. A friend of mine gave me transistors at least a year ago... he was gonna try and fix his 635D, but was hesitant to even to try......I told him I'd fix his after I figured...
audiokarma.org

Also the slider switch that activates the signal when reversing direction often needs some cleaning.
 
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Yep. Did all that replaced 20 transistors, removed both slider switched cleaned them put them back, checked every single solder joint
 
djtchort, did you ever figure out what your issue was? Just curious really. I have a 635D that's playing wonderfully at the moment. My last winter project was a total re-cap of all boards and let me tell you, that was NOT easy! Very time consuming too..took me most of the winter working on it off and on. There's a TON of caps and transistors in that unit. A couple of years ago, mine was going in and out on one channel and wouldn't record on one, so I replaced all the 2SC458's on the operating board and those problems were fixed.
 
I'm sure you've already done it but I would triple check the polarity of the transistors you replaced - and then check again. Good luck.
 
Hi all,
Since this is the latest Akai GX-635D thread, I thought I might post a couple of resources that may be useful.
There is a great video on youtube (
) on restoring and calibration (excellent!)
Part 1 - Akai 635D Restoration (
) - not as detailed as the above video
Akai GX-635D Repair - Won't Do Tape Recording (
) (excellent - use of schematics to trace problems!)
There are others too - youtube could be a resource (taken with a pinch of salt!!!)
Also, for those who don't have the Service Manual (or Owner's manual), I'd be happy to upload them to the AK Database (Unfortunately, the AK Database jumps over the GX635 - has the GX-630 and GX-636) - see https://akdatabase.org/AKview/thumbnails.php?album=57&page=3
Sincerely,
John Graham.
 
murugan19 said:
Hi all,
Since this is the latest Akai GX-635D thread, I thought I might post a couple of resources that may be useful.
There is a great video on youtube (
) on restoring and calibration (excellent!)
Part 1 - Akai 635D Restoration (
) - not as detailed as the above video
Akai GX-635D Repair - Won't Do Tape Recording (
) (excellent - use of schematics to trace problems!)
There are others too - youtube could be a resource (taken with a pinch of salt!!!)
Also, for those who don't have the Service Manual (or Owner's manual), I'd be happy to upload them to the AK Database (Unfortunately, the AK Database jumps over the GX635 - has the GX-630 and GX-636) - see https://akdatabase.org/AKview/thumbnails.php?album=57&page=3
Sincerely,
John Graham.
Click to expand...
Did you have an opportunity to upload the GX-635D service manual? I don't see it in the files. Thanks!
 
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