Revox B77 speed problem

[bogdyy]

hello
i bought from ebay a "working " revox b77 MK1 .when i received , it doesnt hold play , the breaks were weak ,total mess..So i clean it , i replaced most of the capacitors (esspecialy on the procesor board were i replaced the tantalums also) .i have only the power suply capacitors and the motor ones in "original ". i instal new brake sprigs and now the masine works good but only if i have big reels but if i put small reels it doesns work properly:playback speed fluctuates ,it doesnt hold the play function (will play if i press more the 1 2 second the play buton , not the case with big reels) , if i rewind the right motor doesnt stop when it should , it keeps spining because ,i guess, its beend powered after i press the stop button ..also not the case with big reels were i dont have the same problems ..any ideeas were to look? what to do next?
best regards
Bogdan

[MilanMilosevic]

Re: Revox B77 speed problem

Zdravo Bogdane,

due to smaller inner diameter, small (7,5") reels have greater tape tension from takeup (left) reel. To compensate for this, B77 has reel size selector button. If after selecting small reel you still experience the same problem, that measn your left brake is not adjusted as it increases tension force. It is very easy to check if brakes are too tight: in playback, listen carefully above both reel motors if you can hear any friction.

[bogdyy]

Re: Revox B77 speed problem

hello

thank you for your answer but ..i dont think the brakes are my problem ,my problem is still there ever the reel button is pressed or not..i think is somethink electronic..but i dont know what..if i record on smaal reels , the speed is slowing after the half of the tape and the moters even stops and the starst again by itself...i think i need a frequency meter and start digging...
regards

[MilanMilosevic]

Re: Revox B77 speed problem

Bogdan,

I don't think it is the same problem. For now, I recommend you to try readjusting or completely releasing left spool brake and see what happens in playback with small reels. For the rest, I will have to look at schematics and come back later.

[MilanMilosevic]

Re: Revox B77 speed problem

One important thing to check is the condition of your pinchroller. If it has become too soft or sticky, particularly if green type, then it is most likely the culprit.

[bogdyy]

Re: Revox B77 speed problem

hello Milan
i will do that tomorow , i will record a full tape from begining to the end and i will get back with an answer.the roller is the black type , not new but is in good condinion.
thank you very much for this
Bogdan

[bogdyy]

Re: Revox B77 speed problem

hello
even with the brakes removed , i ve got the same problem after the midlle of the tape..

[MilanMilosevic]

Re: Revox B77 speed problem

I think your problem is defective pinchroller - aged and too soft to pull the tape beyond some tension force from the left spool. Try unwinding tape from left spool with finger during playback so that there is no tape tension. Otherwise, try cleaning pichroller and capstan, or borrowing a working one to try.

[tinman]

Re: Revox B77 speed problem

Are you positive that none of your tapes have sticky shed? Do ANY of your tapes leave residue on the guides and heads? A sticky tape will stop the deck.