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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 14th Nov 2019, 11:00 pm   #1
carbotec
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Default Revox A77 Recording Fault

Hi everyone I am a new member and would like some advice on this question. When recording from the Aux input on both channels is loud and clear but when you play the recording the left channel is very low.
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Old 15th Nov 2019, 1:27 am   #2
Ted Kendall
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Default Re: Revox A77 Recording Fault

First port of call is the heads - make sure they are clean. Has the machine worked properly up to now, or have you recently acquired it?
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Old 15th Nov 2019, 7:16 am   #3
TIMTAPE
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Default Re: Revox A77 Recording Fault

The A77 heads are hard to view .A dentists mirror really helps. It can take some time and patience to fully clean heads. These are well made decks
but are now old. There may be other issues...
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Old 15th Nov 2019, 9:57 am   #4
carbotec
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Default Re: Revox A77 Recording Fault

I have just acquired this machine and have purchased some Maxell 10.5" tapes. The tapes have recordings on them which play great. The recorder was serviced 1/11/19 and whilst using it the left meter stopped working so I paid a lower price as the seller didn't want to spend any more on it.When I bought this A77 with the right vu meter non functional I swapped the left meter to the right to see if it worked and it did, I then reinstalled it back to the left side and bought a replacement which is on its way. Then to record I set the left meter to achieve the required level then set the right adjuster to the same level. When switching from input to NAB right sound level dropped slightly but the left level was only just audible.
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Old 15th Nov 2019, 9:51 pm   #5
theoldtrout
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Default Re: Revox A77 Recording Fault

The service manual for these machines is freely available and will help fault finding. Check the PCBs at the bottom of machine where they plug into sockets, re-seating may cure your fault. There are separate boards for each channel so you could do a swap of channels to establish if the fault moves with a board.
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Old 15th Nov 2019, 11:36 pm   #6
Michael Maurice
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Default Re: Revox A77 Recording Fault

I wonder if the tapes are suffering from SSS Sticky Shed Syndrome. You may find its deposited the oxide on the heads, maybe a little more on the record head which has given rise to the fault you described.

Thoroughly clean the heads with cotton buds and Isopropyl alcohol. The only use new tape such as RTM, Zonal and BASF.

One other thing, the calibration pots can fall to pieces, so these may require looking at.
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Old 17th Nov 2019, 12:50 am   #7
jamesperrett
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Default Re: Revox A77 Recording Fault

Quote:
Originally Posted by Michael Maurice View Post
I wonder if the tapes are suffering from SSS Sticky Shed Syndrome. You may find its deposited the oxide on the heads, maybe a little more on the record head which has given rise to the fault you described.
I've yet to see that happen with genuine Maxell tapes although who knows whether some other make of tape has been wound onto Maxell reels. One clue is to check the leader tape as Maxell tapes have distinctive leaders with timing marks on them.

Incidentally Tim, Studer must have thought about the inaccessibility of the heads on the B77 as mine came with a cleaning kit that included a small dentist's style mirror.
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Old 17th Nov 2019, 1:32 am   #8
Michael Maurice
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Default Re: Revox A77 Recording Fault

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Originally Posted by jamesperrett View Post

Incidentally Tim, Studer must have thought about the inaccessibility of the heads on the B77 as mine came with a cleaning kit that included a small dentist's style mirror.

I do wonder why the B77 was designed like that as at the time all semi-pro decks and most if not all Japanese machines had a flat cover with good access to the heads and tape path..
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Old 17th Nov 2019, 12:19 pm   #9
TIMTAPE
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Default Re: Revox A77 Recording Fault

James I think I have somewhere a similar mirror. The PR99 of course rectified this access problem. On my B77 I got so tired of the problem that I modded it. Raised the deck plate to be flush with the swinging alum door. It also meant a small mod to the rh reel movement sensor mounting. The mod didn't do anything for the machine's looks but for my tape transfers, function tends to trump looks.
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