Revox G36 faults

[matt20102]

Greetings, all!

I acquired a Revox G36 two track player from a vintage enthuisiast. At his place, the unit worked quite well but when I got it home, I noticed several annoying problems. First, it seems only to play back on one channel; I'm suspecting tube problems here. The recording is soft on one channel, but this seems to be a common problem with this unit. The most insidious problem, though, is that the transport controls won't stay engaged. I need to hold down the play, FF and RW buttons otherwise they immediately disengage.

The sound quality is exquisite otherwise and the unit seems to be in great mechanical shape. I've cracked the case open looking for obvious faults (broken mechanics, loose connections) but could not find any.

Any ideas?

[rayfutrell]

You can download the German service manual here. http://www.schori.info/b200s/smdownload.htm
Regards,
Ray

[kevinkr]

Resurrecting a dead thread... I just got an G36 MKIII half track machine in pretty good condition. Exterior is a little dirty, and some mouse apparently decided to use it as a food warehouse, but other than that it is in very good condition.

I have pulled it apart and am probably going to replace the supply electrolytics and selenium rectifiers although oddly enough they appear to be good at this point. Preliminary checks with a meter and ballast lamp seem to indicate nothing amiss.

Tubes are all good, and the machine appears to have received little use.

I will clean all of the switch contacts in addition to the planned parts replacements.

Anyone know if the motor snubber and run caps are paper PIO types and do they typically need to be replaced? Getting the right values should be easy enough, getting the right form factor might be another issue.

I'd rather not have magic smoke issues with this machine as mechanically it could last my life time if I take care of it.


Here's a link to an English language manual. (very comprehensive) and a couple of very good restoration related articles:

www.johnmcculloch.net/tapedecks.aspx

My confusion arises because although I am quite familiar with this machine the last time I worked on one was long enough ago that there generally were no concerns about supply caps, the rectifiers or the motor run and snubber caps. The parts used are long lived and apparently noted for that propensity, but now this machine is at least 41yrs old.

As an aside I do plan to reread Charlie King's Glass Audio article, and would recommend it to anyone with one of these decks.

Eventually I plan to get rid of the internal power amplifier, and probably V1/V2 of the tape amplifier as they provide gain I will not normally require.. I can tap right into the recording chain at the recording level pot.

[stevecole]

Hi Matt

Not familiar with the G36, but I can say for certain that an A77 will do just what your machine is doing if you don't have a plug fitted into the "Remote Control" socket. This "Dummy Plug" must also have a shorting link fitted. 'Fraid I don't know which pins you need to link together though!

[kevinkr]

Originally posted by stevecole
Hi Matt

Not familiar with the G36, but I can say for certain that an A77 will do just what your machine is doing if you don't have a plug fitted into the "Remote Control" socket. This "Dummy Plug" must also have a shorting link fitted. 'Fraid I don't know which pins you need to link together though!

Knew I should have started a new thread.. What I get for not taking my own advice and resurrecting an old thread. I'm going to start a new one.