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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 23rd Nov 2023, 10:20 pm   #1
EdGizzard
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Default Revox A700 Capstan not spinning

Hi All,

Capstan Motor not spinning on my A700. Have checked the fuses. All seems fine.

Was going to check the power transistor tomorrow. Will also test motor.

Any thoughts much appreciated. Thanks all.

Service manual link:

https://drive.google.com/file/d/1LqW...ew?usp=sharing
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Old 24th Nov 2023, 12:02 am   #2
TIMTAPE
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Default Re: Revox A700 Capstan not spinning

Hi Ed, has the machine been in recent use? If not I'd test the electrolytic caps on the motor PCB. Silly question: is one of the three speed buttons selected?
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Old 24th Nov 2023, 10:13 am   #3
EdGizzard
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Default Re: Revox A700 Capstan not spinning

Thanks Tim,

Yes 7 1/2 pressed in

Yes been using it recently. Switched it on yesterday but capstan not moving.

Just checked the motor and it seems OK also power transistors seem fine. Will move onto to the PCB. Thank for you help.
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Old 24th Nov 2023, 1:35 pm   #4
EdGizzard
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Default Re: Revox A700 Capstan not spinning

Find attached Capstan Control CD.

I've tested everything on here and all seems good. The AC cap and power transistor that are connected to it are also fine.

I guess I should check the power supply? All other functions on the machine appear in working order.

Any advise on where to start here?

Thanks everyone.

Full Service manual here:

https://drive.google.com/file/d/1LqW...ew?usp=sharing
Attached Files
File Type: pdf Capstan Control.pdf (85.7 KB, 22 views)
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Old 24th Nov 2023, 2:27 pm   #5
EdGizzard
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Default Re: Revox A700 Capstan not spinning

I've tested everything on the Capstan Control board and everything connected to it. 135v AC is coming in.

I guess I should move on to the Capstan speed control board?

Any thoughts much appreciated.

Thanks all
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Old 24th Nov 2023, 3:12 pm   #6
DMcMahon
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Default Re: Revox A700 Capstan not spinning

I note that you above have tested the Control Board but just to mention the capacitor C1 on that board is listed as 0.47uF 150V MP (Metalized Paper).

This is the same description as the capacitors on the Revox A77 Tape Drive board, which generally are Rifa capacitors, on the A77 they sometimes fail/go up in smoke.

David
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Old 24th Nov 2023, 5:13 pm   #7
EdGizzard
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Default Re: Revox A700 Capstan not spinning

Thanks David. I checked that cap. Seems ok.

After putting it all back together it started working!!

Well at least i know a little more about it now. Lets see how we go.

Thanks for your help
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Old 24th Nov 2023, 6:46 pm   #8
Radio Wrangler
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Default Re: Revox A700 Capstan not spinning

Sounds like a dry joint. Might be worth checking for others.

David
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Old 24th Nov 2023, 11:53 pm   #9
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Default Re: Revox A700 Capstan not spinning

Quote:
Originally Posted by DMcMahon View Post
I note that you above have tested the Control Board but just to mention the capacitor C1 on that board is listed as 0.47uF 150V MP (Metalized Paper).

This is the same description as the capacitors on the Revox A77 Tape Drive board, which generally are Rifa capacitors, on the A77 they sometimes fail/go up in smoke.

David
They recently went on my A77 relay board, interestingly the machine kept on working until you unthreaded the tape and then I found that the reel motors were still powered with the machine in STOP. I replaced them all.
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Old 25th Nov 2023, 8:31 pm   #10
Michael Maurice
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Default Re: Revox A700 Capstan not spinning

You MUST replace all the RIFA's on the A700, failure of them can cause serious problems especially in the system control module.

Please do not use the machine until you have done so.
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