Adjusting Revox B77 Tape Transport Question

Archived from groups: rec.audio.tech (More info?)

In article <82a975ca.0410190321.777b0e66@posting.google.com>,
Eric <e.sisi@noos.fr> wrote:
>Hi, I have a nice Revox B77 giving me some trouble. At 3 1/4 with 7"

This is probably described in the maintenance manual, which any number
of people will be happy to sell you on eBay. I haven't worked on a
B77, but the A77 had brakes which applied drag to the feed reel and
replacing or adjusting these was a common maintenance issue.

There were specs on the adjustment, and if this is out of whack then
other things are probably due for adjustment, so I don't think you
can avoid getting the maintenance manual.

I used a few B77's, and liked them better than the A77, especially with
modern (for 1977) tape formulations.

Mike Squires
--

Mike Squires (mikes at cs.indiana.edu) 317 233 9456 (w) 812 333 6564 (h)
mikes at siralan.org 546 N Park Ridge Rd., Bloomington, IN 47408

Archived from groups: rec.audio.tech (More info?)

In <82a975ca.0410190321.777b0e66@posting.google.com>, on 10/19/04
at 04:21 AM, e.sisi@noos.fr (Eric) said:

>Hi, I have a nice Revox B77 giving me some trouble. At 3 1/4 with 7"
>spools, when I press PLAY, the tape gets quite loose on the left side,
>bounces a bit until it stabilises. I notice that when I put a bit of
>pressure on the left spool when pressing play, the tapes does not
>bounce, obviously, but never gets to be in proper contact with the
>head. Tape seem to be a bit far off and I hear the opposite track in
>the background 9very fainth). If I leave it to its own device, the
>tape gets into proper contact. I guess this is just a matter of a
>simple adjustment. Any ideas?
>Thanks,

The back tension is too low.

If you remove the tape, defeat the end of tape sensor, and press play,
both reels should spin, but with low torque. This torque keeps tension
on the tape and takes up the tape spilled out from the pressure roller.
I suspect that there is a problem with the low power routed to the
supply reel motor (during play). If the unit rewinds, then the supply
reel motor is probably OK.

Another poster suggested that this is a brake problem. This is not the
case because the brake bands are released during play or wind. The
brakes are engaged only when the machine is in stop mode. I suggest
that you do not mess with the brakes. I've seen lots of trouble created
by well meaning "servicers" who adjust the brakes. If there is a
problem with the brakes, the machine will have touble stopping or, for
machines stored poorly for a long time, the brake bands may stick to
the drums. (This was much more of a problem on early A77's -- the
orange brake band liners used on the B77's are less likely to stick)

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Archived from groups: rec.audio.tech (More info?)

Detector195@yahoo.com (Detector195) wrote in message news:<6213f73a.0410191617.50acc782@posting.google.com>...
> e.sisi@noos.fr (Eric) wrote in message news:<82a975ca.0410190321.777b0e66@posting.google.com>...
> > Hi, I have a nice Revox B77 giving me some trouble. At 3 1/4 with 7"
> > spools, when I press PLAY, the tape gets quite loose on the left side,
> > bounces a bit until it stabilises. I notice that when I put a bit of
> > pressure on the left spool when pressing play, the tapes does not
> > bounce, obviously, but never gets to be in proper contact with the
> > head. Tape seem to be a bit far off and I hear the opposite track in
> > the background 9very fainth). If I leave it to its own device, the
> > tape gets into proper contact. I guess this is just a matter of a
> > simple adjustment. Any ideas?
> > Thanks,
> >
> > Eric
>
> IIRC the tension on both reels is supplied by running the reel motors
> in a low torque mode. The brakes are only for stopping the transport.
> There is a capacitor to supply the psuedo 3 phase signal to the motor.
> Something might be wrong with that capacitor. I am digging this up
> from my memory of having owned a B77 long ago. For better or worse, I
> sold it after buying a MiniDisc recorder. The B77 was wonderful, but I
> rarely used it because the tapes were so expensive and the whole thing
> was so heavy.
>
> In this case, it is definitely worthwhile trying to dig up a service
> manual.

Guys, thanks for the advice. This ispointing me in the right
direction. I'll keep this post updated.

Thanks again

Eric