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Akai GX-625 runs slow at end of tape

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Hi,

I recently acquired an Akai GX-625 reel to reel deck. This is my first foray into open reel machines so I really don't know anything about how they function. The machine seemed to function ok when the seller demonstrated the machine. Now that I have it home I've discovered that the tape slows down considerably as the tape gets near the end of the reel. When I first heard it at the seller's place we didn't play the tape to the end and I never thought to fast forward the reel. The machine appears to be in good condition and seems to works well but for slowing down of the reels. If I give the supply reel the slightest assistance in spinning tape off the reel the speed picks right up. The same result also occurs if I slightly spin the roller to the left of the head housing.

Does anyone have any insight into what the problem may be? I'm prepared to find a tech to fix the problem. I'm just wondering if this will be an expensive proposition or just a tune-up, so to speak.

Thanks in advance.

John H.

Follow Ups:

RE: Akai GX-625 runs slow at end of tape - steerpike_jhb 10:58:09 07/01/07 (3)
I'd say you've got a worn-out pinch roller. When they get old, they get hard and lose their 'rubberyness', then there is not enough traction when the supply hub gets small (towards the end of tape) and the back tension increases.
Pinch roller replacement is very simple - IF you can find a suitable one. Lots of cheap generic ones around, that may work well enough, although not as good as the original brand.
- Pinch Roller - John H 20:19:40 07/02/07 (2)
  Hi,
  
  Thanks for the reply. The pinch roller seems to have a fair amount of life left in it. Although it does seem less flexible in the center of the roller than at the edges where the tape doesn't contact the roller.
  
  How flexible should it be?
  
  Thanks.
  - RE: Pinch Roller - Steerpike_jhb 08:38:20 07/03/07 (1)
    As i understand things, the pinch roller should be compressable enough that the edges of the roller 'outside' the borders of the tape actually come in contact with the capstan. I.e., the central band of the roller's rubber should be able to be pushed in the thicness of the tape.
    In this way, the capstan doesn't drive the tape so much as the capstan turns the pinch-roller which then drives the tape.
    
    It could be your tape is past its 'best-before' date. Some brands are terrible, some age very well (and how it was stored ha a big effect). The tape should feel absoluely smooth when run between your fingers - no hint of tackiness. Since all models of machine have different tape paths, guide posts etc, the problem may be worse on some models.
    
    In my own cases, I've had more problems winding & rewinding old grungy tape than actually playing & recording it.
    Does your tape rewind fast & smoothly?
    - RE: Pinch Roller - John H 10:43:59 07/03/07 (0)
      The tapes do rewind fast and smoothly.
      
      I'll have to check further to see whether the pinch roller compresses more easily at the edges. I'm at the office now. My recollection is that the roller is softer at the edges.
      
      There is a significant buildup of (iron oxide?) on the roller where the tape makes contact with the roller--the roller winds up with a brown stripe in the center. I've cleaned this a couple of times but it bulds up fairly quickly after it's been cleaned.
      
      The tapes did squeal quite bit when I first tried using them, however the squeal has disappeared for the most part.
RE: Akai GX-625 runs slow at end of tape - X-2000R 18:47:47 06/28/07 (1)
Two possibilities:
One is that the TAPE is what's bad, and not the deck. Tapes that are in early stages of Sticky Shed will gum up the tape path as it plays. But it's not yet so bad as to cause an actual stoppage or create the squealing. By the time most of the length has passed, enough oxide has built up on the idler wheels, guide pins, etc to create enough drag to cause the slowdown you mention. Try checking this out. Clean if necessary, try different tapes and see if that doesn't help.
The other possibility I see is that the decks tension is off. That is either the takeup reel is not applying enough torque to keep up the travel. Although this would more likely manifest itself in the form of tape spill under the headstack and/or pinch roller-which would usually result in partial or complete drop out of the program. But check it anyway. The other side of this same coin is that the supply reel is applying TOO much counter torque and is causing the slowdown. Despite what many of you may think, in forward play, the supply reel is NOT spinning "in neutral" so to speak. A counter tension is being applied to maintain steady tape flow. This is why at the end of the tape, the empty supply reel will suddenly begin spinning backwards just before the end of tape drops the idler wheels and shuts down the deck.
On Teac "X" series decks, this is a relatively simple fix, requiring only a couple turns of a flathead screwdriver on the tension pots. Unfortunately, I have no idea how this works on an Akai deck. But chances are, there is inside the deck, some kind of variable pot that adjusts the tension. Chances are. But again, I could be wrong. But if it does, it should likewise be an easy fix.
Before scouring the Web for a qualified repair shop and dragging the deck down. And spending upwards of a couple of hundred dollars, see if you can't locate (on Ebay or elsewhere) a service manual that will almost certainly cover the topic in question.
Good luck.

Edits: 06/28/07 06/28/07
- Follow-up - John H 19:47:18 07/02/07 (0)
  Hi,
  
  Thanks for the response. I managed to get hold of an older Akai 4000DS which has allowed me to do some experimenting.
  
  Basically, what I started to find with the GX-625 was that pitch variations were occurring on and off throughout the entirety of the tape which became worse and mostly continuous near the end of the tape. I also seemed to notice that the tape played back slower than the CD I was recording from.
  
  First I recorded a CD to the 4000DS at 7.5 ips. The playback on the 4000DS seemed to be fine--no pitch variations, same speed as the CD. When I transferred the tape I made on the 4000DS to the GX-625 the GX-625 played the tape back at a much slower speed than the 4000DS and with about the same amount of pitch variation (present on and off throughout the tape but worse and mostly continuous at the end of the tape).
  
  Secondly I recorded a CD on the GX-625. As I said above, the playback seems slower than the CD playback speed (this seems odd to me as I am assuming, perhaps incorrectly, that the reels travel at the same rate of speed whether in record or playback mode). When I transfer the tape recorded on the GX-625 to the 4000DS the playback seemed to be a bit faster but the pitch was more constant throughout the tape but eventually got worse at the end of tape (though not as bad as when played back on the GX-625.
  
  Based on the foregoing it would appear that the reels on the GX-625 are running slow and at irregular speeds. I've cleaned the heads and rollers on the GX-625 and they seem to remain clean. I believe the tape is circa 1973--so it's pretty old. Could the tape be more of a problem on the GX-625 than on the 4000DS?
  
  I was thinking of ordering some new tape to see how that fares on the GX-625. I'll also find a copy of the service manual in the meantime.
  
  Any thoughts?
  
  Thanks

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