Studer B67 - BOTH reels spinning! Please help. - UK Vintage Radio Repair and Restoration Discussion Forum

david craig · 2nd Mar 2011, 12:10 pm

My Studer B67 MKII has the ‘spinning reels’ problem. I have read all the related threads (here and elsewhere) but my fault seems a bit different. On my recorder BOTH supply and take up reels are spinning!

The recorder was working fine until, having played a tape, I left it powered up but stopped. First thing I noticed was a slight ‘electrical’ burning smell (but NO smoke). Playback (at all speeds) still worked but it wouldn’t wind forwards or backwards. Having powered off, removed the tape and powered back on the supply reel started spinning clockwise and the take up reel anticlockwise - at high speed. Only way to stop them is to power off.

I have had a look (and a smell) inside but there is nothing obvious. The 0.47 uf capacitors on the reel motor boards look intact.

Please can someone advise me.

Thanks very much.

David

SteveCG · 2nd Mar 2011, 1:12 pm

David,

I don't have the circuit diagram for a Studer B67 - perhaps you do or you could get it (its most likely included in the service manual) off the Studer website. Check to see whether the motors are controlled by Triacs. You mentioned looking at other threads and I've just had to replace one Triac (out of 4 in the B77), with the tape-recorder exhibiting a similar fault.

Michael Maurice · 2nd Mar 2011, 1:33 pm

The motors are NOT controlled by Triacs but by power transistors. it is rather odd that both motors are spinning. The motors are controlled from the large logic board, you need a manual before you do any work on it. They are complicated beasts.

david craig · 2nd Mar 2011, 1:43 pm

Thanks both. I have a manual (and a multimeter) but I am not an electronics engineer by training. Do you have any suggestions as to how to narrow this down? Thanks

David

backstreets · 2nd Mar 2011, 3:11 pm

Hi!

I'll try to contribute with something even though I'm still trying to figure out my own B67 Mk2... the other thread right next to this one

To start with you probably want to disconnect "pin 8" from the following PCB boards:

Spooling Motor Ctrl/Supply M1 (1.167.764)
Spooling Motor Ctrl//Take Up M2 (1.167.768)

Look at the schematics in the manual for details. You see on the schematic that "pin 8" is marked that it comes from the Tape Transport Control PCB. Unplug that pin 8 crimp connector removes the Tape Transport Control PCB from the equation (the board that lies horizontally to which play, ff, stop etc. buttons/switches are fastened to).

1. If the motors stop then the problem is likely on the Transport Board.

2. If the motors continue the problem is elsewhere. The 0.47uF caps on the Spooling boards, the power transistors, something on the PSU board etc.

But at least you'll know wheter it's the control board with all the logics on it or not. If they stop when pin 8's are disconnected, I think your problem might be more advanced and located on the Transport board. If they still you might have a quite simple fix for it... maybe

That's about what I can say with my knowledge, I'm still quite a newbie when it comes to repairing these things

Michael Maurice · 2nd Mar 2011, 6:28 pm

I've spoken to David and he has arranged to bring the machine to me to look at.

With these machines ALL the 0.47uf capacitors must be replaced with AC types, I use class X, normal 0.47 capacitors will NOT be ok.

Looking at the diagram, me thinks the -12V supply may have failed.

Ted Kendall · 3rd Mar 2011, 11:12 am

This sounds awfully like what happened with my A700s at one point. Both spooling motors took off in opposite directions with the brakes on as soon as the machine was powered. Eventually, I found some tracking on the control buttons on the transport board. With this cleaned off, normal operation was restored. That said, the absence of any of the three rails from the transport board (they are all fused) can produce similar results.

Michael Maurice · 3rd Mar 2011, 11:26 pm

Fortunately these machines use a standard op amp and not the TCA561 found in the A700.

That said, these op amps run from +12V & -12V if the -12V supply was missing then the outputs from these op amps would rise and turn on the motors.

All will be revealed when David brings the machine up to me.

Ted Kendall · 4th Mar 2011, 10:22 pm

Not too sure about that - if memory serves, the Mk1 used 561s, but the Mk2 didn't - very late A700s had the later pattern of transport board as well...

david craig · 11th Mar 2011, 10:14 am

First, many thanks to everyone who responded to my query - particularly Michael. I'm really impressed by your knowledge and helpfulness!

This is just to say that having replaced all the 0.47 caps on the motor boards the problem is now fixed. There were clear signs of burning/splitting on at least one of the caps on both supply and take up motor boards.

Best wishes

David

2nd Mar 2011, 12:10 pm	#1
david craig Triode Join Date: Mar 2011 Location: Battle, East Sussex Posts: 25	Studer B67 - BOTH reels spinning! Please help. My Studer B67 MKII has the ‘spinning reels’ problem. I have read all the related threads (here and elsewhere) but my fault seems a bit different. On my recorder BOTH supply and take up reels are spinning! The recorder was working fine until, having played a tape, I left it powered up but stopped. First thing I noticed was a slight ‘electrical’ burning smell (but NO smoke). Playback (at all speeds) still worked but it wouldn’t wind forwards or backwards. Having powered off, removed the tape and powered back on the supply reel started spinning clockwise and the take up reel anticlockwise - at high speed. Only way to stop them is to power off. I have had a look (and a smell) inside but there is nothing obvious. The 0.47 uf capacitors on the reel motor boards look intact. Please can someone advise me. Thanks very much. David

2nd Mar 2011, 1:12 pm	#2
SteveCG Nonode Join Date: Jun 2009 Location: Herefordshire, UK. Posts: 2,495	Re: Studer B67 - BOTH reels spinning! Please help. David, I don't have the circuit diagram for a Studer B67 - perhaps you do or you could get it (its most likely included in the service manual) off the Studer website. Check to see whether the motors are controlled by Triacs. You mentioned looking at other threads and I've just had to replace one Triac (out of 4 in the B77), with the tape-recorder exhibiting a similar fault.

2nd Mar 2011, 1:33 pm	#3
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,225	Re: Studer B67 - BOTH reels spinning! Please help. The motors are NOT controlled by Triacs but by power transistors. it is rather odd that both motors are spinning. The motors are controlled from the large logic board, you need a manual before you do any work on it. They are complicated beasts.

2nd Mar 2011, 1:43 pm	#4
david craig Triode Join Date: Mar 2011 Location: Battle, East Sussex Posts: 25	Re: Studer B67 - BOTH reels spinning! Please help. Thanks both. I have a manual (and a multimeter) but I am not an electronics engineer by training. Do you have any suggestions as to how to narrow this down? Thanks David

2nd Mar 2011, 3:11 pm	#5
backstreets Retired Dormant Member Join Date: Feb 2011 Location: Helsinki, Finland Posts: 22	Re: Studer B67 - BOTH reels spinning! Please help. Hi! I'll try to contribute with something even though I'm still trying to figure out my own B67 Mk2... the other thread right next to this one To start with you probably want to disconnect "pin 8" from the following PCB boards: Spooling Motor Ctrl/Supply M1 (1.167.764) Spooling Motor Ctrl//Take Up M2 (1.167.768) Look at the schematics in the manual for details. You see on the schematic that "pin 8" is marked that it comes from the Tape Transport Control PCB. Unplug that pin 8 crimp connector removes the Tape Transport Control PCB from the equation (the board that lies horizontally to which play, ff, stop etc. buttons/switches are fastened to). 1. If the motors stop then the problem is likely on the Transport Board. 2. If the motors continue the problem is elsewhere. The 0.47uF caps on the Spooling boards, the power transistors, something on the PSU board etc. But at least you'll know wheter it's the control board with all the logics on it or not. If they stop when pin 8's are disconnected, I think your problem might be more advanced and located on the Transport board. If they still you might have a quite simple fix for it... maybe That's about what I can say with my knowledge, I'm still quite a newbie when it comes to repairing these things

2nd Mar 2011, 6:28 pm	#6
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,225	Re: Studer B67 - BOTH reels spinning! Please help. I've spoken to David and he has arranged to bring the machine to me to look at. With these machines ALL the 0.47uf capacitors must be replaced with AC types, I use class X, normal 0.47 capacitors will NOT be ok. Looking at the diagram, me thinks the -12V supply may have failed.

3rd Mar 2011, 11:12 am	#7
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,675	Re: Studer B67 - BOTH reels spinning! Please help. This sounds awfully like what happened with my A700s at one point. Both spooling motors took off in opposite directions with the brakes on as soon as the machine was powered. Eventually, I found some tracking on the control buttons on the transport board. With this cleaned off, normal operation was restored. That said, the absence of any of the three rails from the transport board (they are all fused) can produce similar results.

3rd Mar 2011, 11:26 pm	#8
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,225	Re: Studer B67 - BOTH reels spinning! Please help. Fortunately these machines use a standard op amp and not the TCA561 found in the A700. That said, these op amps run from +12V & -12V if the -12V supply was missing then the outputs from these op amps would rise and turn on the motors. All will be revealed when David brings the machine up to me.

4th Mar 2011, 10:22 pm	#9
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,675	Re: Studer B67 - BOTH reels spinning! Please help. Not too sure about that - if memory serves, the Mk1 used 561s, but the Mk2 didn't - very late A700s had the later pattern of transport board as well...

11th Mar 2011, 10:14 am	#10
david craig Triode Join Date: Mar 2011 Location: Battle, East Sussex Posts: 25	Re: Studer B67 - BOTH reels spinning! Please help. First, many thanks to everyone who responded to my query - particularly Michael. I'm really impressed by your knowledge and helpfulness! This is just to say that having replaced all the 0.47 caps on the motor boards the problem is now fixed. There were clear signs of burning/splitting on at least one of the caps on both supply and take up motor boards. Best wishes David