Fluttery Revox B710

[SaSi]

I have a Revox 710 that I need to repair in order to keep. Well, I can keep it unrepaired, but no fun there...

The problem is that PB speed is unstable and somewhat slow. W&F is terrible - speed is drifting up and down severely, actually.

I have cleaned the pinch rollers and lubricated the shafts, checked the pinch pressure with the solenoid, and did some experiments removing pressure from either rollers and reducing / increasing pressure on both in increments.

End result is that removing the left pinch roller reduces this instability considerably but not below being audible. Removing the right one, increases that, and also reduces PB speed to a creeping level - almost.

I have also checked the capstan shafts and lubricated them carefuly and sparingly. No change.

Furthermore, it appears that the problem is increasing as I play the deck more. If it runs for 20min or so, it becomes unbearable. If I leave it cool down for a couple of hours and start again, for the first couple of minutes it plays perfectly.

I have gone through the SM and beyond several adjustments, no mention of troubleshooting such problems.

Any ideas out there?


ADDED:
I have no clue if that is related, but I notice that really quickly, the pinch solenoid becomes hot. It is almost so hot that I can barely touch it with a finger. Is that normal?

[vincedog3]

If memory serves me well, this deck was a direct drive capstan drive. A 3 motor affair. Wow, trying to remember, that is hard. Sounds like if had been any other cassette deck the capstan drive belt is failing and needs to be replaced. I think the B710 was direct drive so no belts, but you may have a motor problem, or a problem with the servo that maintains the speed if applicable, or a problem that is logic concerned that controls the speed of the capstan motor. Just my 2 cents, hope it helps. Great deck, and I hope you get it fixed. Love Revox gear.

[SaSi]

Vince - thanks for the reply.

I worked on it a little more after I posted.

Firstly, it is a 4 (no less) motor deck. Two servo motors for the capstans and two direct drive motors for the reels. BTW, the whole construction appears to be very similar to the R2R decks by Revox, only smaller - and not in every part of the deck.

I have also noticed another problem that is generated by heating up. The REW reel motor becomes sticky - makes noise / vibration rather than turn. Cooling of fixes everything again.

I tried disconnecting the REW motor and running the deck without it. Speed and w&f are now perfect, however back tension is missing and playback is bad.

I also switched pinch rollers (LHS <--> RHS) and found out that one of the rollers is bad, causing wow. (Actually the deck isn't fluttery, it's wowy...).

So, I guess I am after rollers and a general dismantling to reach the LHS spool motor, open it up and find what's wrong.