Fostex R8-tape reels slowing to a stop on playback.

Mr Fruit

Mr Fruit

New member
Ok , following on from my other thread, Ive come to the conclusion that the speed fluctuations i was getting on playback probably are not due to:

1:Sticky shed- no residue on anything.
2: Pinch roller- got a new one
3:main drive belt- its not toothed, but the rubber looks in good condition, and it isnt slipping. you can see the plastic wheel that is attatched to the motor shaft, and the pinch drive wheel, and there is no slipping. (see pic below)

The most worrying thing is that on playback, or recording, the tape spools and drive capstan slow down, and after 10 or so seconds slow to a halt completely. If you spin them manually they pick up a bit, but they are definately poorly.

I can only conclude that it is a main drive motor problem.

What the next step?

Any opinions?
 
Picture074.jpg


Picture066.jpg


Picture065.jpg


fostex.jpg
 
Does anyone know if new motors are availble for this machine?

Ive contacted the company, which was taken over a while ago, and they have not been able to help......:(
 
yeah, thought as much.


Unfortunately, they dont even have a contact email it seems, so I cant ask them, as they are in the states, and im not.:(
 
Found a vintage audio guy who is going to do a bit of research, says he MAY be able to fix it but its a bit modern for him......:p
 
I have an idea. I won't say it's a very good idea, in fact it's a pretty bad idea, like "Let's make a TSR-8 into a half-inch stereo deck" bad, but it's an idea nonetheless. If you're not afraid of a little metalwork and electronics hackery it may be possible.

You see, I believe that the capstan motors for the Tascam 32/34/38 are still available. AFAIK these are more-or-less self-contained, with the drive system on a daughterboard that's part of the motor assembly, so it may be possible - with a number of likely irreversable modifications - to use one of those instead. You would lose all hope of syncing the machine as a slave because direct capstan control won't be possible. It will almost certainly run at the wrong speed, though you can probably fix that with the varispeed circuit, an MRL tape and a frequency counter.

What you would need to do is figure out a way to mount it exactly where the current capstan motor is, so that you can use the current belt. This may be tricky but is almost certainly possible. You would also have to wire the control lines so that the motor is in 15ips mode and attach the varispeed line to the appropriate pot on the front of the deck. It may be arranged in a different configuration to the '32 varispeed pot so that would need some research.
Finally, you would have to make sure that it was given the right voltage. They're probably both 24v, so you may be able to feed it from the existing transport voltage on the power suppy but you'd have to check first.

This is borderline insanity, but if it's a choice between that and selling the deck for parts, it's a possible option.
 
jpmorris said:
I have an idea.
the drive system on a daughterboard that's part of the motor assembly, .
Click to expand...

Is the daughter board a device like the bit of circuitboard thats attatched to the motor in the picture above?


jpmorris said:
.
You would lose all hope of syncing the machine as a slave because direct capstan control won't be possible.
.
Click to expand...

if i could just get it to record a track, i would be 100% happier than i am now, never mind syncing it up to somthing else....



jpmorris said:
What you would need to do is figure out a way to mount it exactly where the current capstan motor is, so that you can use the current belt. This may be tricky but is almost certainly possible. .
Click to expand...


That part would be ok, im good with metalwork.



jpmorris said:
You would also have to wire the control lines so that the motor is in 15ips mode and attach the varispeed line to the appropriate pot on the front of the deck. It may be arranged in a different configuration to the '32 varispeed pot so that would need some research.
Finally, you would have to make sure that it was given the right voltage. They're probably both 24v, so you may be able to feed it from the existing transport voltage on the power suppy but you'd have to check first.
Click to expand...

Thats the bit thats a problem.

Id have to find someone who was competant to do that, as Im not an electronics guru really.

The information is much appreciated though, as at the moment, its the only viable suggestion that I have had........thanks JP:)
 
My apologies - it looks like the capstan system on the 30-series TASCAM machines is not self-contained, it's just that the capstan control board is omitted from all the schematics and unlabelled (why ?!?).

CHS are selling the '38 capstan motor for about £104 (+VAT, I suspect) but I don't know if that includes the controller as well. If not, forget it. If they do, it's still a bit of a long shot - I haven't quite been able to work out what the supply voltage is for the 30-series capstan motor either, though I suspect it's 24v. Less than 35 I think, as that's what one of the capacitors is rated at.
I might be able to find out by stripping down my '32, but that is not a prospect which thrills me.
 
jpmorris said:
that is not a prospect which thrills me.
Click to expand...


With a tiny bit of luck, that may not be necessary.

Now, I dont know whether Im being hopeful, foolish, or just plain old delerious, because Ive just stripped it all down again, and found that the white plastic wheel that is the top drive wheel of the main drive belt (the one attatched directly to the motor) is indeed, as suggested spinning like a bastard on the motor spindle!:eek:

Woohoo! :D

Is it too early to be a bit optimistic?:eek:

Im sure that shouldn't be happening, unless it works like a clutch, which I severely doubt........thats got to be the problem hasnt it?

Right im going back in......get your thinking hats on for how I can stop it spinning......


I think I may just have glimpsed the light at the end of the tunnel!!!!:)
 
Mr Fruit said:
Is it too early to be a bit optimistic?:eek:
I think I may just have glimpsed the light at the end of the tunnel!!!!:)
Click to expand...

It's a huge step forward, and demystifies the symptoms completely.

What I worry about is the ability to affix or replace the plastic pulley, but so goes it for plastic pulleys and the hallmark of Fostex quality. The main premise of Fostex was to get their narrow format machines to market by focusing on affordability, functionality and sound quality. IMO, in the turnaround they cut a lot of corners on quality. Plastic pulleys being only one example. Fostexes are overall more plastic than TEACs, and they break out similarly on serviceability.

As for myself who's followed your posts,... you've nailed the cause which is a huge step forward. The actual fix may be tenuous still at this time. Good luck!

/DA
 
A Reel Person said:
It's a huge step forward, and demystifies the symptoms completely.

What I worry about is the ability to affix or replace the plastic pulley, but so goes it for plastic pulleys and the hallmark of Fostex quality. The main premise of Fostex was to get their narrow format machines to market by focusing on affordability, functionality and sound quality. IMO, in the turnaround they cut a lot of corners on quality. Plastic pulleys being only one example. Fostexes are overall more plastic than TEACs, and they break out similarly on serviceability.

As for myself who's followed your posts,... you've nailed the cause which is a huge step forward. The actual fix may be tenuous still at this time. Good luck!

/DA
Click to expand...

Tenuous, but where theres a will........:)


Ok, heres the problem.

very shiny spindle, either chromed, but probably stainless....



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Nylon type pulley wheel, both items have quite a hard, shiny surface.

It was bound to slip at some point.

Picture186.jpg



the pulley wheel will only go on to the shaft from one side.

it has a miniscule slot, which I thoght at first may be a crack, but i think it to allow it to widen a little to accept the shaft.

it will only slide onto the shaft a a specific distance, then stops, I cant see why, but it does, which is good, because I tore it off quite quickly in my haste, and then worried about belt alignment.

So........


How to keep it on.

I think if i just superglue it, it may break the grip again, under load, as both surfaces are pretty shiny.

Im going to clean both with tape head cleaner first.

Threadlock?

Maybe a light file on the shaft/ scoring of the nylon wheel to provide adhesion?
 
Congratulations. I'm not honestly sure what the best idea is either. I'll admit, superglue was my first thought, but as you say, it's probably not the most permanent solution.

Good luck with it.
 
Also not sure but it's great that it's not the motor. Many a time it's just something simple masquerading as a more complex problem. Man, Fostex sure didn't play around cutting costs..:eek::D;)
 
I would suggest a good cleaning of both parts with iso alcohol and then using a two-part epoxy...just figure you're never going to get them apart again without breaking something. That will hold them though...obviously it was a friction-fit from the factory so the torque on that union can't be that much. You could even try something as simple as a piece of carefully placed clear tape around the shaft and see if that gives the pulley enough bite.

For less permanent you could try the threadlock but I'd use the red and not the blue.

Congrats BTW. You'll get it.

it looks like the capstan system on the 30-series TASCAM machines is not self-contained, it's just that the capstan control board is omitted from all the schematics and unlabelled (why ?!?)
Click to expand...

This is somewhat of a mystery to me too...my Tascam 58 has not parts list or PCB layout for the Capstan Servo PCB in the manual. There is a schematic though which was helpful for determining what caps were needed for it. It also is a completely spearate PCB board deep in the bowels of the 58 and why there are none of the aforementioned docs for it like every other PCB in the machine I don't know. It is interesting though that the board and components appear to be manufactured at a different location or time...maybe Teac outsourced those components? Wierd.
 
I think Im going to try roughing up the surfaces a bit, then as you say, 2 part epoxy.

If that doesnt work, ill have a word with the CAD people at work, and see if they can make another wheel with a grub screw to clamp on to the shaft.

As a matter of interest, the bottom pulley is cast aluminium.........
 
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