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Reel To Reel All discussions pertaining to reel to reel decks. These include general usage, recording, playback, and service questions. For subjects related to tape itself, see the Open Reel subforum under this one. Obscure service subjects that don't quite fit go in the Help and Do It Yourself subforum.

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  #1  
Old 07-21-2014, 03:50 AM
Trigoner Trigoner is offline
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Revox PR-99 mk3 weird transport issue: need help

Hello everyone,
This is my first post here though I,ve been looking around here for a year: lots of valuable information.
well, I bought a year ago a Revox PR-99 mk3 with butterfly heads in almost new condition. Iīm very happy with it bit I recently discovered that it doesnt play big reels properly..
During playback of 10.5 reels , it stops after 12-14 minutes. This only happens with big reels (it plays 7" reels flawlesly) and seems to be related with the take up reel : when the take up reel is almost full, it stops after a couple of minutes only.
Any idea of what the problem is?
Thanks.
  #2  
Old 07-21-2014, 04:16 AM
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steerpike steerpike is offline
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This could be related to not enought torque on the take-up reel. If there is insufficient tension on the right hand side of the headblock, tape will slip over the counter roller, rather than turning it: this will trigger an auto-stop.

OR it may be the bearing of the counter roller is dry & giving too much friction.

When it is running, with a 10-inch reel, try to feel or judge how much take-up tension it has. Does it feel similar to the back tension on the left-hand side ?

Too little take up tension will be caused by motor capacitor problems or something not right in the power supply.
  #3  
Old 07-21-2014, 05:20 PM
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Nakdoc Nakdoc is offline
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I vote for reel motor bearings. Each motor has two. In my experience lubrication alone will not get the bearing to behave. You will find bearings sets listed by searching for Revox parts.
  #4  
Old 07-22-2014, 03:36 AM
Trigoner Trigoner is offline
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Quote:
Originally Posted by steerpike View Post
This could be related to not enought torque on the take-up reel. If there is insufficient tension on the right hand side of the headblock, tape will slip over the counter roller, rather than turning it: this will trigger an auto-stop.

OR it may be the bearing of the counter roller is dry & giving too much friction.

When it is running, with a 10-inch reel, try to feel or judge how much take-up tension it has. Does it feel similar to the back tension on the left-hand side ?

Too little take up tension will be caused by motor capacitor problems or something not right in the power supply.
Yes, it feels similar tension on both sides, I canīt see anything abnormal.. I know all the capacitors were replaced by the seller and hope this is caused by some mechanical failure becouse Iīm not very good with electronics.
I think this reel recorders have a tension arm in both sides and maybe this could need to be adjusted/replaced (I once made a mistake playing 10" reels with the small reel button selected).
Another reason could be the one suggested by Nakdoc, althouh replacing motor bearings coud exceed my limited aknowledge..
  #5  
Old 07-22-2014, 04:27 AM
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steerpike steerpike is offline
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The Pr99 (all revoxes in fact) have no adjustments for reel tension. There are just two setings, seected by changing a votage tap on the tranformer. So there os nothing to go out of adjustment.

If the tension is OK, then the fault must be in the roller to the right of the pinch roller, that is not turning freely.
Do you notice that the counter shows any accumulated error after a long period of playing (compared to a watch)?
  #6  
Old 07-22-2014, 07:19 AM
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Skywavebe Skywavebe is online now
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Like most people that work on these machines I would have to see what it is doing as a lot can be left out with the listing of a symptom. In fast wind mode do the bearings make noise? It has been my experience that quiet bearings that are worn will make themselves known in a higher speed. If they re completely quiet then I would make sure the roller on the exit side of the head is rolling. These things can need oil or in some cases where ball bearings are used they need to be replaced.
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Old 07-22-2014, 01:50 PM
Trigoner Trigoner is offline
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Well, after all , it seems the problem was related with the IR sensor..
I just put black tape on it and.. it works. Donīt know why but now my Revox PR-99 MK3 can play a 10" reels from the beginning to the end.
Anyway, I canīt explain why the recorder could play 7" reels..
  #8  
Old 07-22-2014, 02:17 PM
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Maybe the tape was such that the IR went through the tape where the 7" reel was thicker? I still indicates there is an adjustment of some kind needed. I am not sure it there is a IR sensitivity control or not.
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Past Teac/Tascam Lead Service Technician at Chicago Factory Service still doing repairs.
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  #9  
Old 07-22-2014, 03:27 PM
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A tape with bad shedding can leave a "window" of missing oxide that would trigger the IR stop.
  #10  
Old 07-23-2014, 08:27 AM
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steerpike steerpike is offline
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Some B77s had a sensitivity trimmer for the auto-stop sensor. If present, it will be a thumb-wheel trimpot on the tape-drive-control board, the horizontal one just below the take up motor.

It's unusual for a 10.5" reel to have "optically thin" tape on it, I've noticed on the extra long play 7" reels the Revoxes can become unhappy, but that is really thin tape, and best avoided.
  #11  
Old 07-23-2014, 01:25 PM
Trigoner Trigoner is offline
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In fact, the 7" reel tapes were maxell 35-90B and the 10" tapes are brand new RMG LPR 35. I think both have the same thikness (550m vs 1100m) but who knows..
Iīm happy that I could solve the problem (2 days without an issue) so easily because itīs an awesome machine with rare butterfly heads in pristine condition and it bothered me so much pressing the play button every 5 minutes.
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