Fostex R8 speed fluctuation-revised, with pics.

[Mr Fruit]

Yes, there is a service manual for the R8, I recieved a message from Sweetbeats the other day, saying thast he had a copy.

There is space for a circlip, but it doesnt have one on, so thats another item on the shopping list, once my roller and belt have arrived from Japan.

strange that they should change the design of the roller and the capstan, they seem to be the other way round on yours.

 

[carlholland]

Following on from this thread:

https://homerecording.com/bbs/showthread.php?t=281264

Ok Chaps, after ruling out sticky shed syndrome, the problem seems to lie with either:

1. The pinch roller
2. the drive belt
3. the motor.

Here is the pinch roller.

I have a link to buy a new roller, but its in Japan, and it may not be the cause of my problem.

Ok...the front of the machine.

In this pic, I have drawn on where the drive belt runs, behind the facia.

If you press play, the motor runs the untoothed belt, and turns the pulley with the capstan on it. the pinch roller closes on to it, which should pull the tape through, and it does, but on playback, there are massive speed and therefore pitch fluctuations.

If I hold the capstan or the motor pully, the motor slows down and struggles to speed up again. if you give the capstan a quick twist, it will speed up again. If you hold the roller so that you stop it from turning, it will not start again, until you give it a twist.

To me, in my admittedly unexperienced opinion, this seem like a weak motor.

if the motor was strong, surely, if i held the capstan, it would make the drive belt slip.

heres the motor from behind.

I reckon its the motor.

Anyone else have an opinion?

Are these motors still available?

Thanks in advance.

Phil.

I am working on my R-8 at this time and found the problem that you have decribed and I beleive that I have found the culprit , it looks like the belt that moves the captan the white pulley that is at the bottom was slipping on the shaft that is connected to the captan. I have taken it apart and put it back on with RTV blue silicone and in a few hous will fire it up for a test run, but I am confident that ,that was it. carlholland@att.net

 

[carlholland]

Following on from this thread:

https://homerecording.com/bbs/showthread.php?t=281264

Ok Chaps, after ruling out sticky shed syndrome, the problem seems to lie with either:

1. The pinch roller
2. the drive belt
3. the motor.

Here is the pinch roller.

I have a link to buy a new roller, but its in Japan, and it may not be the cause of my problem.

Ok...the front of the machine.

In this pic, I have drawn on where the drive belt runs, behind the facia.

If you press play, the motor runs the untoothed belt, and turns the pulley with the capstan on it. the pinch roller closes on to it, which should pull the tape through, and it does, but on playback, there are massive speed and therefore pitch fluctuations.

If I hold the capstan or the motor pully, the motor slows down and struggles to speed up again. if you give the capstan a quick twist, it will speed up again. If you hold the roller so that you stop it from turning, it will not start again, until you give it a twist.

To me, in my admittedly unexperienced opinion, this seem like a weak motor.

if the motor was strong, surely, if i held the capstan, it would make the drive belt slip.

heres the motor from behind.

I reckon its the motor.

Anyone else have an opinion?

Are these motors still available?

Thanks in advance.

Phil.

I am working on my R-8 at this time and found the problem that you have decribed and I beleive that I have found the culprit , it looks like the belt that moves the captan the white pulley that is at the top was slipping on the shaft that is connected to the motor. I have taken it apart and put it back on with RTV blue silicone and in a few hours will fire it up for a test run, but I am confident that ,that was it. carlholland@att.net

 

[jpmorris]

If I remember correctly, he found - and posted in another thread - that the root of his problem was actually the capstan pulley on the motor itself. It had cracked or something and was basically freewheeling. AFAIK he managed to fix that somehow.

 

[carlholland]

Following on from this thread:

https://homerecording.com/bbs/showthread.php?t=281264

Ok Chaps, after ruling out sticky shed syndrome, the problem seems to lie with either:

1. The pinch roller
2. the drive belt
3. the motor.

Here is the pinch roller.

I have a link to buy a new roller, but its in Japan, and it may not be the cause of my problem.

Ok...the front of the machine.

In this pic, I have drawn on where the drive belt runs, behind the facia.

If you press play, the motor runs the untoothed belt, and turns the pulley with the capstan on it. the pinch roller closes on to it, which should pull the tape through, and it does, but on playback, there are massive speed and therefore pitch fluctuations.

If I hold the capstan or the motor pully, the motor slows down and struggles to speed up again. if you give the capstan a quick twist, it will speed up again. If you hold the roller so that you stop it from turning, it will not start again, until you give it a twist.

To me, in my admittedly unexperienced opinion, this seem like a weak motor.

if the motor was strong, surely, if i held the capstan, it would make the drive belt slip.

heres the motor from behind.

I reckon its the motor.

Anyone else have an opinion?

Are these motors still available?

Thanks in advance.

Phil.

I just got thru working on my R-8 and problem solved it was the white spindle on the motor shaft that drives the capstan it was just loose enough to do everything that you describe with you issues I hope you get it worked out if you need any assistance I will be glad to help you in any way. What I did to remedy the problem was I took a thin peice of paper and cut it where it would slip in the hole and I pushed it onto the shaft be careful as you can you too much and end up shattering that white spindle. I tried the RTV silicone but it didnt work. carlholland@att.net

 

[jpmorris]

https://homerecording.com/bbs/showpost.php?p=3164980&postcount=16
...Mr Fruit used Araldite.

 

[Mr Fruit]

Yep, after slightly roughing the spindle.

 

[mishisle]

I too am having the pitch/speed fluctuations. I've attached some pics of my roller and belt. Do you think they need replacing?

 

[mishisle]

Oh and turns out my pulley wheel has a crack in it so that's probably what's causing the speed/pitch problems.