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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 20th Jan 2023, 7:45 pm   #1
xbsa666
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Default Revox B77.

Hi, I'm new here. And have an issue with the Revox B77 and just want to ask your thought about the issue I have, I've been searching forums and had found no answer yet. So the issue is with Recording on B77 I must keep my finger on the play button (after pushing record and play at the same time). If I remove my finger the record lights go off and the machine stops spinning. everything else works great playing and even recording levels and voltages are fine. Im a mechanical engineer and restore those machines as a hobby, this one put my dead in a track it is fully restored and cleaned most of Capacitors are replaced i got a kit from revox-online .com I did one last year worked without a problems. All calibrations are done and like i said performs flawlessly just that issue with recording, i suspect the Oscillator card or even audio integration board a specially REC LED's. thanks for input.
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Old 20th Jan 2023, 8:10 pm   #2
Ted Kendall
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Default Re: Revox B77.

Welcome aboard! First thing to check is that the autostop is working properly - put a piece of paper in front of the IR sensor and see if the machine runs in record. It may be that the additional load in Record is affecting the autostop's trigger threshold.
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Old 20th Jan 2023, 10:41 pm   #3
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Default Re: Revox B77.

Does this only happen in record or does it happen in playback too?
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Old 21st Jan 2023, 12:29 am   #4
Michael Maurice
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Default Re: Revox B77.

I would suspect one or both of the 2200uF 40V capacitors on the power supply board.

In record, the machine draws a bit more current which can bring the voltages down just enough to not work correctly.

I had this once before only in my case, none of the functions worked correctly. A check on the 24V unregulated line showed it to be 23V which dipped to 19V when any function was selected.
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Old 22nd Jan 2023, 1:56 am   #5
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Default Re: Revox B77.

Thanks for your thoughts, I recapped power supply board completely I will check 2200 caps they can be faulty.
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Old 22nd Jan 2023, 1:57 am   #6
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Default Re: Revox B77.

Quote:
Originally Posted by jamesperrett View Post
Does this only happen in record or does it happen in playback too?
Yes it happens only in record mode it plays fine.
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Old 22nd Jan 2023, 1:58 am   #7
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Default Re: Revox B77.

Quote:
Originally Posted by Ted Kendall View Post
Welcome aboard! First thing to check is that the autostop is working properly - put a piece of paper in front of the IR sensor and see if the machine runs in record. It may be that the additional load in Record is affecting the autostop's trigger threshold.
IR works fine I checked it already.
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Old 22nd Jan 2023, 2:00 am   #8
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Default Re: Revox B77.

Quote:
Originally Posted by Michael Maurice View Post
I would suspect one or both of the 2200uF 40V capacitors on the power supply board.

In record, the machine draws a bit more current which can bring the voltages down just enough to not work correctly.

I had this once before only in my case, none of the functions worked correctly. A check on the 24V unregulated line showed it to be 23V which dipped to 19V when any function was selected.
I recapped the power supply recently with new caps, one or both can be faulty, voltage actually drops to about 21V when i press record and play
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Old 22nd Jan 2023, 3:07 pm   #9
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Default Re: Revox B77.

Maybe a daft question, but is the remote control plug( with appropriate wire links) present?
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Old 22nd Jan 2023, 5:39 pm   #10
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Default Re: Revox B77.

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Maybe a daft question, but is the remote control plug( with appropriate wire links) present?
The remote control blanking plug doesn't need to be present on the B77. It should work fine with nothing plugged into the connector.
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Old 22nd Jan 2023, 6:09 pm   #11
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Default Re: Revox B77.

Quote:
Originally Posted by xbsa666 View Post
I recapped the power supply recently with new caps, one or both can be faulty, voltage actually drops to about 21V when i press record and play
That is where your problem lies
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Old 22nd Jan 2023, 11:14 pm   #12
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Default Re: Revox B77.

Quote:
Originally Posted by Tim View Post
Maybe a daft question, but is the remote control plug( with appropriate wire links) present?
no there is no plug here. and it worked before recapping
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Old 22nd Jan 2023, 11:20 pm   #13
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Default Re: Revox B77.

Quote:
Originally Posted by Michael Maurice View Post
Quote:
Originally Posted by xbsa666 View Post
I recapped the power supply recently with new caps, one or both can be faulty, voltage actually drops to about 21V when I press record and play
That is where your problem lies
Thanks, ordered new Hichicon 2200uF 60V caps, one cap I installed is faulty testing shows shorted. I got a cap kit from Revox on line, one I guess was a dud. Did not test them before installation. will replace both with Gold audio quality will see the results.
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Old 23rd Jan 2023, 6:06 pm   #14
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Default Re: Revox B77.

Quote:
Originally Posted by Michael Maurice View Post
Quote:
Originally Posted by xbsa666 View Post
I recapped the power supply recently with new caps, one or both can be faulty, voltage actually drops to about 21V when I press record and play
That is where your problem lies
Caps replaced, still same problem as soon I release play button LED's go off and recording stops voltage is 24.09V This is MYSTERIOUS?!?!?
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Old 24th Jan 2023, 12:40 am   #15
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Default Re: Revox B77.

What is the voltage of the 24V unregulated supply off load? it should be around 28V and around 24V when a function is selected.
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