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Universal Capstan Motor
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  #1  
Old 06-12-2011, 01:43 PM
yockmyer yockmyer is offline
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Akai GX-635D woes

Greetings one and all,

I recently purchased an Akai GX-635D reel to reel player. I always wanted a R2R deck and the price was too good to walk away from. I was assured by the owner that it worked when last he used it but.......
I got it home and and deoxited and lubed the various switches and mechanisms.I did this prior to trying the deck out.
After reassembly, I set up for play. That's when I discovered the following issues: the unit plays fine when playing forward, but when I stopped the tape and hit reverse, the solenoid clicks, the tape moves a bit, then shuts off.
Rewinding and fast forwarding are very labored, slowing down to a complete stop before finishing. I tried rewinding and FF'ing directly, i.e. bypassing the transport, and the issue remains. All the threads I have looked at seem to deal with transistor issues.
If anybody has any ideas at all, I would be grateful....I'd really like to get this beauty up and running. Thank you in advance.....
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  #2  
Old 06-12-2011, 02:36 PM
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Skywavebe Skywavebe is online now
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Hi Yockmyer,
There are plenty of people that know more about this unit than I. But from what you say, you are maybe dealing with an old machine that needs some oil in the motors- try to see if there are oil tubes around. Take the brake off and see if there is a friction to the motor as there should be little. Otherwise- and you should be able to see the Capstan belt might need to be replaced as it might be stretched. Just some ideas to check out- I may have had this model for a two week period. Of course that did not last while I worked at Teac.
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Old 06-12-2011, 03:23 PM
yockmyer yockmyer is offline
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Sam..
Thank you for your reply. I took the brakes off and the motors seem to be friction free. Now comes the part where my stupidity shows. Is the capstan belt you spoke of the tiny belt up there near the motors? If so, that belt does seem loose. Thank you again for your reply!!!
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Old 06-12-2011, 03:53 PM
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macman007 macman007 is offline
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I would think the tiny belt is for the tape counter if I'm not mistaken. The main belt is usually wider and flat.
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Old 06-12-2011, 04:15 PM
yockmyer yockmyer is offline
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macman007,
Upon closer inspection, you're absolutely right. I am not certain, but I don't think there is a capstan belt, as it is a direct drive R2R. But, I most certainly could be mistaken. Thanks for your reply!
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  #6  
Old 06-13-2011, 10:53 AM
yockmyer yockmyer is offline
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Any other suggestions?????
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Old 06-13-2011, 11:40 AM
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tapetech tapetech is offline
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Verify that the brake solenoid engages (which turns brakes off) in all four modes: play, reverse play, fast forward and rewind.

Verify that your tape is not defective. Many old tapes become sticky and will adhere to heads and guides. Try the deck with a new tape or one that you know is not sticky.

Verify that the pinch roller is good: not rock hard and not soft/sticky and that it rotates freely and that the arm that moves the roller up and down moves freely. Tape the tension arms in the up position, put the deck into play without tape and verify that the pinch roller firmly engages the capstan shaft in both directions. Also verify (still without tape) that in play mode the pinch roller rotates at the same speed in both play directions.
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Old 06-13-2011, 04:02 PM
yockmyer yockmyer is offline
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Tapetech:
Thank you for your reply....the brake solenoid does indeed engage in all four modes. The tape may or may not be defective as I only have 2 used recorded tapes to work with. Will search for new unused tape. I cleaned the pinch roller and used some rubber renewer on it,,,took off the sheen and isn't sticky. And the pinch roller does indeed rotate at the same speed in both directions.
I noticed when I removed the plastic reel some scuffing from the tables. Could the tables be indented too far? I am clueless to the operation of the deck and surely appreciate the help of you and the others.
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Old 06-13-2011, 05:19 PM
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tapetech tapetech is offline
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The reels should not touch the front panel at all. Put on an empty reel on the right table, tape the tension rollers up and then hit FF. Should spin very fast. Put reel on left hub and hit REW. Should spin fast as well.

If reel tables are pushed in, loosen the set screws for the reel hubs and adjust height so that the tape runs in the center of the reel flanges.


Also make sure you deck is set to 120 volt and not 220.
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  #10  
Old 06-13-2011, 06:15 PM
yockmyer yockmyer is offline
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I did and they do. Fast spin on both tables. The empty I have is a metal reel, as opposed to the full reels which are plastic.
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  #11  
Old 06-13-2011, 08:17 PM
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Sounds like the deck is operating correctly. You may have defective tape.
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  #12  
Old 06-15-2011, 02:49 PM
dutch_frank dutch_frank is offline
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Quote:
Originally Posted by tapetech View Post
Sounds like the deck is operating correctly. You may have defective tape.
I think so too..... Try to wind or rewind without a tape threaded. I know it's difficult because in fact you need a third hand to keep the two tension arms in the 'free' position (so not locked) plus you need to press the REW or FFWD button. If the motors are powerfull and cannot easily be stopped with your hands then I think the electronics are fine and you're probably dealing with sticky tape. When you buy new tape please carefully clean the tape guides and heads with alcohol first otherwise the remains of the old sticky tape may 'infect' your new tape. And don't buy new old stock Ampex #407 and such. They may come sticky out of the box. I would suggest you try Maxell.
And, also interesting to learn is that the GX-635D does not have belts inside other than a counter belt. Both the capstan and the reel tables are direct drive.
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Old 06-15-2011, 04:14 PM
Bob Boyer Bob Boyer is offline
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Do you have any alcohol (not rubbing) or head cleaning fluid? If so, clean the heads - see if you get a bunch of gunk. If so, you've got some sticky shed tapes for sure. I'll add my voice to that chorus as it seems the machine works properly otherwise.

Don't use them anymore - I would think it's really hard on the motors.

Good luck. New RMGI tape is available from several vendors online, including FullCompass.com.
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Old 06-15-2011, 04:35 PM
yockmyer yockmyer is offline
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Thank you for your replies...
dutch_frank...the motors run strong with nothing threaded, but in opposite directions. Stupid question time, but is this normal?
Bob Boyer...I cleaned the heads as soon as I got the machine home using 99% isopropyl alcohol. Though dirty, it wasn't extremely so. I guess it must be the tapes but I have tried 6 of 15 and have the same result.
tapetech...thank you for the info provided. Will get hold of some new tape and take it from there.
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Old 06-15-2011, 07:51 PM
Bob Boyer Bob Boyer is offline
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yockmyer,

I got a number of reels of old Ampex 407 (and maybe a few early Quantegy 407s) from the campus radio station a couple of years ago when I was first getting back into the game; most of them were bad and I had to throw them out. I think 4 were okay, but I didn't record anything on them I couldn't re-record if/when they go bad as well...

It's just part of the deal these days and a primary reason that people are trying to command such high prices (or bidders are driving prices to insane levels) for Maxell NOS reels on fleabay. I prefer new tape from the folks who are still manufacturing it but it has its own issues as well, as a perusal of some threads in the Tape subforum will indicate.

Have fun with it once things get sorted out - it's a pretty machine, for sure.
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Old 06-15-2011, 11:08 PM
eleromimpex eleromimpex is offline
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Good morning!
1.Immobilize the arms tensioner in the middle position with some electrical adhesive tape(do not use other tape,it can stick permanent to Al panels!)
2.Hit REV taste. You should hear the relays and main heads switches clicking inside,then the left motor must turn clockwise and right motor counterclockwise.The torque of left motor must be so strong that it will be very hard to stop it with fingers.
3. The torque on right motor should be not so hard,you must be able to stop it with fingers and even rotate it in the clockwise sense(as it is turned when tape is used in REV mode). Do that and let me know, Regards!
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Old 06-16-2011, 03:38 AM
dutch_frank dutch_frank is offline
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Quote:
Originally Posted by yockmyer View Post
Thank you for your replies...
dutch_frank...the motors run strong with nothing threaded, but in opposite directions. Stupid question time, but is this normal?
Bob Boyer...I cleaned the heads as soon as I got the machine home using 99% isopropyl alcohol. Though dirty, it wasn't extremely so. I guess it must be the tapes but I have tried 6 of 15 and have the same result.
tapetech...thank you for the info provided. Will get hold of some new tape and take it from there.
Yup, that's normal. When you press the forward play button (>) the reel tables turn in the opposite direction but the power of the left reel motor is much weaker than the right. This is because the left reel motor gives a little so called 'backtension'. When you press the reverse play button (<) it's the other way round.
Isopropyl alcohol is the right fluid to clean the heads.
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Old 06-16-2011, 08:30 AM
eleromimpex eleromimpex is offline
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Defective tape (glued,sticky)creates the same problems regardless direction of use(forward or reverse) .Your deck works fine in forward,so..Dirty heads has nothing to do with transport problems.In order to help,I need to know if left and right motors passed the tests described in my previous message. P.S. As electronic engineer ,I am servicing myself the AKAI reel to reel collection since 1988,so it is an pleasure to provide support for other AKAI fans.
PS 2 ON AKAI GX 635-636 ,only left tensioner is active,so you do not need to keep both on active position durring tests,only the leftone

Last edited by eleromimpex; 06-16-2011 at 09:14 AM.
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  #19  
Old 06-17-2011, 01:08 PM
yockmyer yockmyer is offline
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Both motors did indeed pass the tests....I keep wondering if the tables might be recessed a bit too far.... I cannot thank you enough for all for your replies...I am truly chomping at the bit to get it up and running. With the weekend approaching, I will devote more time to it. Again, I thank you all.
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Old 06-18-2011, 05:03 AM
eleromimpex eleromimpex is offline
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Next step: without tape,keep left tensioner immobilised in middle position and press REV. The pinch roller must be pushed up against capstan motor shaft and start rotating...What is happening now?
a.the roller keep rotating till you press stop b.the roler start rotating but slow down and stop in few seconds ,but remain in active position(pressing the shaft) c. the roller stop rotating in 1 -2s,then retract to stop position itself.
An useful alternative test: load one tape,run PLAY FORWARD 5 min.to be shure that tape is not sticky,then push REV and help with right hand the right reel to rotate clockspring sense. What is the result? This will help the LH motor to collect the tape even the motor is in bad shape(on REV mode,LH motor must generate the greatest torque to ,,pull " the tape.). ?
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