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Revox A77 takeup Reel torque

H

hsingh

New Member
Hi ! I need some help regarding Revox A77. Most three direct drive motor reel to reel Taperecorders have resistances to control voltage to the takeup motor and supply motor but in Revox A77 I'm talking about has same torque in takeup reel in fast forward and playback mode. High torque in fast forward is understandable but in playback mode this torque should be less. I don't know whether this model is meant to operate like this or there is something wrong with it. Kindly advise.
 
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Hi,
I would say that it is faulty. Revox machines usually drop the voltage to the motors with transformer tappings and not resistances. Sounds like there is some relay problems there.

GPS16
 
I have an A77, almost positive it does not have same torque in play as FF, Don't have time today but I can look at mine this week. I don't have a schematic I'll check HiFiEng
 
+1 on the relays. Or the spark-supress caps that are connected to the relays. Those have a 99% failure rate and should be replaced anyway.
 
Hi ! Thanks everyone for your kind help for giving me tips in finding out torque problem in takeup spool on Revox A77. I started off by removing one leg of each capacitor on relay board. The torque on takeup motor became absolutely normal as soon as I removed a round capacitor's leg on the left hand side of relays. I have not yet replaced it.
 
Hi ! I would like to share my experience with Revox A77. As far as its performance is concerned everything is fine but what I did not like was a Bearing on the left hand side of tape transportation in Head area and a bush on the right hand side after capstan. What happens is in rewind mode it puts too much strain on this bush which makes the rewind quite slow. I replaced that bush with a bearing and since then it's rewind & forward has become much smoother than ever before. I don't understand the logic of having bearing on one side and bush on the other. One can notice this thing on most Akai Taperecorders also. I don't think having a bearing after capstan will have any negative effect on sound quality. I recently bought Revox C278 which also has the same concept of using bush after capstan. I came across a post in some Forum where a person was complaining of slow rewind/ffdd on this advanced Revox machine. The problem is not there in motors provided the torque is correct but it's the bush which does not let the tape run smoothly. All professional Reel to Reel use bearings on both sides which of course causes less friction on Tapes and improves machine's performance.
 
I have repaired 100+ Revox 77 series decks and I can assure you that the stationary guide on the right does not cause slow rewind. 100% positive. There are many possible causes of slow rewind:

-defective, sticky tape (sticky shed syndrome)
-tape deposits in tape guides
-wrong or missing washers in right or left tape guides (causing the guide to be too narrow)
-low/wrong motor torques
-dragging brakes

Yes, in theory, putting a roller in the right guide may increases FF and REW speeds, but it would only be a very small increase.. Something you would have to measure to notice.
 
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