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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 5th Sep 2019, 9:54 am   #1
QUADGOD
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Default Revox B77 mk2 advice on heads

Just bought a nice recorder for spares but maybe it's too good for that.
Do these heads just need a clean or am I missing something and they need replacing?
I think the brown gunk is oxide off an old tape? I tested it with a rubbish tape and it recorded and played as it should. Brakes and fast forward/ rewind also very good braking as it should with no issues. Cosmetically excellent only one owner and just domestic use. Heres a photo of heads..thanks..
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Old 5th Sep 2019, 10:05 am   #2
lesmw0sec
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Default Re: Revox B77 mk2 advice on heads

Yes, the brown stuff looks like accumulated oxide. Will clean off easily with some surgical spirit on a cotton bud, followed by a dry wipe. The heads are a little worn, but still serviceable.
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Old 5th Sep 2019, 12:33 pm   #3
QUADGOD
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Default Re: Revox B77 mk2 advice on heads

Thanks.
I've no idea how to check (if that's possible) to see if it will play my own pre recorded tapes without setting up bias allignment etc by a pro?
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Old 5th Sep 2019, 12:45 pm   #4
lesmw0sec
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Default Re: Revox B77 mk2 advice on heads

Quote:
Originally Posted by QUADGOD View Post
Thanks.
I've no idea how to check (if that's possible) to see if it will play my own pre recorded tapes without setting up bias allignment etc by a pro?
Bias is not used on replay, so you should be able to play existing tapes, even when the recording side is down. The only issue is head azimuth, which should be OK if not messed with.
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Old 5th Sep 2019, 12:47 pm   #5
SteveCG
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Default Re: Revox B77 mk2 advice on heads

You don't need any bias alignment just to replay tapes. If you have not already tried then I suggest you try one that does not have great value first, just in case there are tape transport problems that could stretch or snap the tape. Ideally you would demagnetise the heads and tape path as well just in case they have become magnetised and so would slowly wipe your tapes on repeated replaying. But first try the tape recorder out and see what, if any, problems it has.

Last edited by SteveCG; 5th Sep 2019 at 12:48 pm. Reason: crossed posting
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Old 5th Sep 2019, 1:00 pm   #6
Ted Kendall
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Default Re: Revox B77 mk2 advice on heads

I'd say those heads have plenty of life left in them. The recommended replacement point on these heads is a flat width of 4mm on the head face. In practice, largely because of the guttering above and below the tape path, the head will take a re-lap or can continue in use. I ran one rep head (being skint at the time) for as long as it sounded OK. One day the top fell away drastically on one side. At that point the flat was nearly 6mm and the gap on the bad side was visible. I'm not suggesting you do the same, but it does indicate that these heads last a long, long time, and that they retain decent performance, on replay anyway, until the pole-pieces are almost worn away.
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Old 5th Sep 2019, 7:55 pm   #7
QUADGOD
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Default Re: Revox B77 mk2 advice on heads

I also need to replace the counter belt. Is this straight forward? I've not removed any covers yet.
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Old 5th Sep 2019, 8:51 pm   #8
Ted Kendall
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Default Re: Revox B77 mk2 advice on heads

Not too bad - you have to detach one end of the RH brake band - one circlip and a spring - to get the belt over the hub. Make sure you note which hole the spring is in and don't touch the brake band surface or the drum with your fingers. If you do, it's out with the acetone to get the grease off.
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Old 8th Sep 2019, 4:51 am   #9
TIMTAPE
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Default Re: Revox B77 mk2 advice on heads

Quote:
Originally Posted by Ted Kendall View Post
I'd say those heads have plenty of life left in them. The recommended replacement point on these heads is a flat width of 4mm on the head face. In practice, largely because of the guttering above and below the tape path, the head will take a re-lap or can continue in use. I ran one rep head (being skint at the time) for as long as it sounded OK. One day the top fell away drastically on one side. At that point the flat was nearly 6mm and the gap on the bad side was visible. I'm not suggesting you do the same, but it does indicate that these heads last a long, long time, and that they retain decent performance, on replay anyway, until the pole-pieces are almost worn away.
Speaking of the guttering on these heads, on some old Revox play heads which were worn down that the guttering slots almost disappeared, I had a machinist deepen the slots. Here's the result.
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