Studer A807 duff rewind - UK Vintage Radio Repair and Restoration Discussion Forum

Ted Kendall · 31st Aug 2020, 9:02 am

Here's a funny one.

Play and Fast Forward normal.

Rewiind usually OK on first operation of the day. Then develops a fault as follows:

Rewind sequence begins normally, but after a couple of seconds the tension arm deflects upwards by about 10mm because the back tension from the take-up motor increases. Naturally enough, the tape eventually slows to a stop. The rewind tension trim pot has no effect at this point but works OK when the fault is not present.

R35, the main set-up pot on the spooling board, is set up as per manual, likewise the two pots on the tension sensor.

Two suspect components replaced, neither of which had any effect - C2 on the spooling board, which is on one of the inputs which are summed to give a tension reading, and the 4520 on the command board which derives the 1/16th tacho frequency used in parts of fast-wind. I guessed that the fault conicided with the software gear change between the two tacho signals. Anyway, it's time for some serious poking. As control of the transport is shared by the command and spooling boards, I may swap out the former and see if I can exonerate some of the system.

jascha · 9th Sep 2020, 9:05 am

Hi Ted,
Any luck with your Studer? I recently had a lot of help from a guy on the TH forum who is based in the USA and he could help you out with it. Mine was more to do with defective Eproms though, which perhaps might be the case?
Hope you find the fault . Good luck.

TIMTAPE · 9th Sep 2020, 10:07 am

Maybe an intermittent connection, perhaps in a multiplug connector. I did have a similar fault on the take up tension PCB of my A700. I think the problem was an electro.

I'm always wary of pcb's which on the upwards facing side have been exposed to dust and corrosion over a long period. Lost count of the number of corroded through PCB tracks I've had to laboriously bridge. I recently removed the main PCB from a customer's B67 just to clean off all the accumulated dirt even though there was nothing at fault. Just long term preventative stuff.

31st Aug 2020, 9:02 am	#1
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,674	Studer A807 duff rewind Here's a funny one. Play and Fast Forward normal. Rewiind usually OK on first operation of the day. Then develops a fault as follows: Rewind sequence begins normally, but after a couple of seconds the tension arm deflects upwards by about 10mm because the back tension from the take-up motor increases. Naturally enough, the tape eventually slows to a stop. The rewind tension trim pot has no effect at this point but works OK when the fault is not present. R35, the main set-up pot on the spooling board, is set up as per manual, likewise the two pots on the tension sensor. Two suspect components replaced, neither of which had any effect - C2 on the spooling board, which is on one of the inputs which are summed to give a tension reading, and the 4520 on the command board which derives the 1/16th tacho frequency used in parts of fast-wind. I guessed that the fault conicided with the software gear change between the two tacho signals. Anyway, it's time for some serious poking. As control of the transport is shared by the command and spooling boards, I may swap out the former and see if I can exonerate some of the system.

9th Sep 2020, 9:05 am	#2
jascha Hexode Join Date: Nov 2005 Location: Kent, UK. Posts: 332	Re: Studer A807 duff rewind Hi Ted, Any luck with your Studer? I recently had a lot of help from a guy on the TH forum who is based in the USA and he could help you out with it. Mine was more to do with defective Eproms though, which perhaps might be the case? Hope you find the fault . Good luck.

9th Sep 2020, 10:07 am	#3
TIMTAPE Octode Join Date: Jul 2006 Location: Perth, Western Australia Posts: 1,969	Re: Studer A807 duff rewind Maybe an intermittent connection, perhaps in a multiplug connector. I did have a similar fault on the take up tension PCB of my A700. I think the problem was an electro. I'm always wary of pcb's which on the upwards facing side have been exposed to dust and corrosion over a long period. Lost count of the number of corroded through PCB tracks I've had to laboriously bridge. I recently removed the main PCB from a customer's B67 just to clean off all the accumulated dirt even though there was nothing at fault. Just long term preventative stuff.