TEAC 32-2B Tape falling from heads during play/record

flyingace

Active member
On the supply side, the pinch roller/capstan makes a squeaking noise as the tape starts getting squirrelly and then drops down from the play/record heads. This is new since I put it in storage last year (climate controlled).

I have thoroughly cleaned the tape path (99% alcohol for heads, a cleaner from Athan on the pinch rollers (I bought new pinch roller from them for my MS-16, the pink solution they sell is good and not alcohol based), I also lubed both posts on the rollers with machine oil as spec’d in the manual. Still happening.

When I put a thumb on the supply reel it cinches back up and works just fine.

Is this simply a sign that the pinch rollers are just trashed and need to be replaced? or could it be the belt that runs inside for the capstan motor?
This unit is known as a closed-loop double capstan model and supposedly the supply side capstan runs at a slightly different speed from the take up side based on ??? This is according to the manual, but not sure.

Any advice what to look at next? I’d like to verify other options before spending the $$ on new rollers only to find it’s something else… which I know, it very well could be ANYTHING when it comes to vintage mechanical gear.

THANKS ALL!

 
Last edited:
I’ll make that video in just a little bit. I’m using ATR MDS-36. I have some Recording the Masters LPR-35 that I haven’t tried yet. Thanks for the help!
 
The video zooms in partway in. I need to see the whole tape path including supply and takeup reels.

Have you checked tensions? What’s the capstan drive mechanism? Is there one capstan motor and two drive belts?
 
The video zooms in partway in. I need to see the whole tape path including supply and takeup reels.

Have you checked tensions? What’s the capstan drive mechanism? Is there one capstan motor and two drive belts?
Sorry, I thought that angle would be best since the heads are so hidden up there, harder to see from a whole tape path view. i can do another though.
I have not checked tensions yet, I’ve never opened this unit up, but I do have the service manual.
From what I can tell, it’s one capstan motor and two belts. Most sellers only sell one belt saying that the second belt is no longer available and most people just bypass it.
It’s likely out of my wheel house to do much here but I’ll try.
Thanks, look for next vid tomorrow.
 
Single motor, single belt. There is another belt but it’s a counter belt, not capstan. If you’ve got the original belt my hunch is the belt is slipping. The takeup pulley is slightly smaller than the supply side pulley creating a mechanical constant tension system. But if the belt is slipping it will slip first on the smaller pulley. You may also need to remove the capstan shafts, and clean and lubricate the shafts and sleeve bearings. That’s where I put my money. I would also check your pinch roller pressures.

36C78A74-D583-4CB4-AD60-C9890069EDB6.png
 
Sadly I agree, but those rollers probably need to be replaced too. I got this one for $300, that’s probably about $100 in rubber plus labor. Is it worth it?
So, do I get to the belt from the back or by dismantling the front? The service manual is unclear.
The 32-2B is the same as the X-2000r.
 
The explanation of the tension, linked to from the other site seems very unscientifically worded. we have a belt around two identical pulleys, driven with a single motor, and the 'explanation' states that the section between the right pulley and the motor spindle is 'stronger' than the return to the left pulley from the spindle. because of rotational forces and friction, the tension in the return path is clearly lower than on the right hand side where tension is higher, but the belt speed is constant, and if the pulleys are the same diameter, then rotational speed will be the same - UNLESS - continuous slippage in the system takes place. I wonder if it is slippage that is causing the issue. The most likely location would be on the right hand pinch wheel. If it slips, at any point, and the left one does not, then the tape between goes slack?
 
If you put pressure on the right hand pinch wheel so it grips the tape strongly as it passes through - does the slippage happen? If it doesn;t then maybe the spring pressure is a bit lacking, or the rubber surface not as soft as it should be?
 
The explanation of the tension, linked to from the other site seems very unscientifically worded. we have a belt around two identical pulleys, driven with a single motor, and the 'explanation' states that the section between the right pulley and the motor spindle is 'stronger' than the return to the left pulley from the spindle. because of rotational forces and friction, the tension in the return path is clearly lower than on the right hand side where tension is higher, but the belt speed is constant, and if the pulleys are the same diameter, then rotational speed will be the same - UNLESS - continuous slippage in the system takes place. I wonder if it is slippage that is causing the issue. The most likely location would be on the right hand pinch wheel. If it slips, at any point, and the left one does not, then the tape between goes slack?
The thing is, any mechanical constant tension system I’ve encountered is always based on some degree of “slippage” to function. I’m surprised the pulleys are the same size, and the explanation of how it works doesn’t make sense looking at the pulley and motor configuration…the takeup capstan is at the end of the drive chain, the supply capstan is at the beginning because of the rotational direction of the motor and capstan shafts. If I had one here I’d be curious to measure the diameter of the capstan pulleys with a dial caliper. I don’t see how it works unless there is a slight difference in the diameter of the pulleys, though I also acknowledge on an auto-reverse consumer model that wouldn’t work because then the pulleys would have to change size. We know that’s not the case. They other way this works is if there is some slight variation in the pinch roller pressure, slightly greater at the takeup side, that would cause more wrap of the tape on the takeup capstan and create that constant tension. So maybe that’s how it works. But, unfortunately, at least as far as the X-10/X-10R service manual goes (I have nothing on the 32-2 in my library), it’s a poor service manual because it covers no theory of operation information, which IMO is essential for understanding a machine and being able to troubleshoot. @flyingace does your 32-2 service manual include any operational theory information?

There is some fairly critical information in the X-10/X-10R service manual about setting pinch roller stroke and pressure, and it says if the pressures are out of spec you have to replace the whole assembly as it is not adjustable…! :eek: This is the epitome of a consumer-grade machine if I can be a little snooty…so if the 32-2 is essentially a Tascam-badged X-10 series machine I’d call it one notch below “pro-sumer”. @flyingace does your 32-2 service manual include this information about checking pinch roller stroke and pressure?

With all this discussion my hypothesis is reinforced: you need to replace the drive belt, clean and lubricate the capstan shafts and bearings, check pinch roller stroke and pressure for each side…basically execute some standard maintenance procedures and go through the setup in the manual and see where things are at. I think it may be a combination of issues with all of those points.

As a related aside the term “closed loop” is being used. I don’t know if Teac used that term or not, or whether that’s used on the interwebs…I don’t typically see that term used regarding a dual capstan drive, it’s usually associated with the geometry of the tape path…most audio tape machines are open loop, where the loop beginning is at the supply reel, and the loop end is at the takeup reel, vs a “closed-loop” tape path where there is a second loop inside that greater loop. I think this started in the instrumentation field. The 3M M23/56/64/79 machines are a good example of a closed-loop machine…here is my M64:

D981946A-EC89-43E8-919A-EDC35D164572.jpeg

3M’s Mincom Division adapted their instrumentation transport for audio in the early 1960s with the M23. They monikered the tape path their “isoloop” design based on the isolated closed-loop design, closed-loop because of the geometry, and “isolated” because of the mechanical constant-tension design…the top black circle in the center is the capstan shaft. It’s about 2” in diameter. Tape enters the path through a set of fixed guides at the top left of the loop and then pass over the capstan shaft, then across the erase and record heads, around the reversing idler at the bottom, then over the playback head, and then again over the capstan shaft and out the exit guides. On the 1/4” machine the capstan shaft surface is comprised of a series of a flat plateau with flat valleys on either side, like a really shallow square wave. On the wider format machines there are multiple plateau and valley sets. There are pinch rollers on the left and right of the capstan shaft, but they are different. The left roller presses the tape against the valleys, and the right roller presses the tape against the plateau, so effectively the tape is being pressed against a slightly greater diameter shaft on the right. This creates a constant tension over the heads and reversing idler, and isolates tape in the closed loop from the supply side holdback tension and takeup side takeup tension as well as any mechanical noise or scrape flutter before or after the isolated loop. It works…and works well…it’s genius. Here are closeup views of the capstan shaft surface and the dissimilar pinch rollers:

FE9832C0-F791-4417-8964-765CE8DF8107.jpeg

CA18D46B-AD21-4014-9F8F-C9B981371710.jpeg

My point is that the “closed-loop” term isn’t related to the dual capstan contact, it has to do with the geometry of the tape path. The dual capstan contact creates an isolated loop or section of tape. So the Teac X-10 series and Tascam 32-2, if my understanding is correct, are open-loop, but they *do* have an isolated tape path section through the headblock assembly because of the dual capstan.
 
Last edited:
I've been sideways thinking - to 16mm projectors I used run, and these often had more than one powered sprocket and just an idler that ensured the film was taut. With audio machines that can run both ways, there surely must always be scope for the tape between the driving points to have different tensions - so as this isn't a common problem, we can assume the system worked, until like now it doesn't. Something is slipping - and it's almost certainly the right hand drive - so something is adrift. I suppose it does do it on all tapes, and does it with full left or right spools in case it's take up torque not helping? Could it even be tape based? As in tape that is less 'grippy'. I guess it's out of our hands really.
 
Fascinating. Some threads I just read. Got nothing to contribute, but lots of info to absorb.
 
If takeup reel tension is ever “helping” pre-capstan tape tension, it means there is a problem with the capstan drive…in other words a properly operating capstan, and I’m talking about the kind we’re talking about here, a small diameter capstan shaft with a pinch roller, isolates the tensions that come before and after it. Takeup tension in a typical tape path like this is there to keep a loop from developing between the capstan and takeup spool, and supply holdback tension is there to mitigate surging and to ensure proper tape-to-head contact. The capstan is moving the tape. That’s in a single capstan system. In a dual capstan system like flyingace’s 32-2, the dual capstan array provides the tension for proper tape-to-head contact, and holdback tension is still there to mitigate surging, and keep the pre-capstan tape and components under tension.

@rob aylestone I think your suggestion is really good regarding applying some pressure to the takeup side pinch roller, to see if that eliminates the loop in the headblock. That would affirm we have something to address with the capstan drive array, either a gummed up capstan shaft, slipping belt, improper pinch roller stroke, pressure, of some combination or some or all of the above.
 
Are those tension arms supposed to be fully up all the time? It looks very wrong to me because on most machines they should be roughly at half travel in normal operation. I'd be checking the reel motor control system to see why the motors seem to be at full tension all the time.
 
Back
Top