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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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4th Apr 2020, 2:01 pm | #1 |
Diode
Join Date: Apr 2020
Location: Istanbul, Turkey.
Posts: 2
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Revox B77 MK II slowing problem
Thanks so much to get me in the community. I wish all of you and the human being overcoming the struggle against the corona virus. I'm a medical doctor (Cardiovascular surgeon) in Istanbul. Recently I've begun in interesting with vintage reel to reel tape recordings and bought some of them from second hand sellers. My problem is, one of my devices (Revox B77 MK II) slows down both while recording and playback when exceeding the half of the reel band. Is there anyone experiencing such a problem and can help me. Thank you.
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4th Apr 2020, 6:17 pm | #2 |
Moderator
Join Date: Feb 2006
Location: Wembley, Middlesex
Posts: 7,225
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Re: Revox B77 MK II slowing problem
What tape are you using, if its old stock from say the 80's and 90's then it could be suffering from Sticky Shed Syndrome.
What size spools are you using, if 10½" ones, try pressing the reel size selector to the small spool position. If the tape speeds up then the problem is due to the tape. If you were to rewind the tape and start again, is the speed correct? If it is then again it points to SSS. |
5th Apr 2020, 12:55 am | #3 |
Octode
Join Date: May 2007
Location: Liss, Hampshire, UK.
Posts: 1,875
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Re: Revox B77 MK II slowing problem
I'd agree with Michael - sticky shed is the most common reason for tape slowing down part way through the reel. It is vitally important to thoroughly clean the machine after any tape that has shed as any sticky remains of the tape could cause other tapes to slow down.
However, it is also important to set the tape tension switch to the correct reel size. If you try to play a reel with a very small hub on the large hub setting it will probably slow down towards the end of the reel. |
5th Apr 2020, 3:18 pm | #4 | |
Octode
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,969
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Re: Revox B77 MK II slowing problem
Quote:
The problem in my experience is normally pinch roller pressure too low, pinch roller rubber gone hard, or the capstan shaft rough finish has been polished smooth. It is often a combination of all three. The pinch roller pressure can be adjusted but a hard pinch roller needs to be replaced and the smooth capstan shaft needs to have the finish roughened by an expert. Also the B77 is not designed for reels smaller than 7" diameter. A 5" or smaller reel on the left side will probably slow down the tape travel even if everything else is correct. The inside diameter of the reel which must be no smaller than 2 3/8", which is a standard 7" reel. Hope this helps. Tim |
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5th Apr 2020, 10:59 pm | #5 | |
Octode
Join Date: May 2007
Location: Liss, Hampshire, UK.
Posts: 1,875
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Re: Revox B77 MK II slowing problem
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6th Apr 2020, 12:27 am | #6 |
Octode
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,969
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Re: Revox B77 MK II slowing problem
Yes we might get away without speed issues with a 5" reel or even smaller when played right to the end if it's switched to "small", and the machine is in top mechanical condition.
But the Revox specs (for the 3.75/7.5 IPS models) state: "Reel size: Up to 10.5" diameter (minimum hub diameter 2.36 inches). Tape tension switchable for small hub diameters." (B77 MkII Service Instructions) A standard 7" reel has a hub diameter of about 2.36". That's all the performance the machine is guaranteed for. The 7.5/15IPS model seems to have more leeway in my experience probably because the capstan shaft being of larger diameter presents a larger surface area to grip the tape. Also in these types of machines, the pinch roller does not drive the tape. It only presses the tape onto the capstan shaft. Whereas in a machine like an Otari MX5050, the pinch roller being much wider than the tape, is itself driven by the shaft and so assists in driving the tape. But on smaller diameter capstan shafts this can damage the tape, hence the pinch roller only touches the tape, not the shaft. Last edited by TIMTAPE; 6th Apr 2020 at 12:42 am. |
7th Apr 2020, 12:32 am | #7 |
Octode
Join Date: May 2007
Location: Liss, Hampshire, UK.
Posts: 1,875
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Re: Revox B77 MK II slowing problem
That would explain it as my experience is with the high speed version. Single masters occasionally come in on 5" reels.
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7th Apr 2020, 1:13 am | #8 | |
Octode
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,969
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Re: Revox B77 MK II slowing problem
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