Revox G36 motor caps advice please

[jascha]

Hello everyone,

I’m in the middle of restoring my G36 and whilst I have the front separate from the back to carry out maintenance on the motors (clean old grease and replace bearings etc) and replace caps on the push button module with x2 type, I would like to take the opportunity to replace the motor run caps.
Taking apart a G36 is very time consuming so it’s worth doing all I can to service it.

Could I get advice please if these Kemet caps in the link below would work well on the G36? These are rated at 3.5uf 5%. I would welcome advice please and if these won’t do the job where can I get a set for my machine please? As I’m in the UK I’m trying to find stock in this country right now.

Also could I find out what type of diodes are used on the push button modules? Are they standard silicon diodes ? Would something like a 1N4001 work as a substitute?

Here is the link..
404 - File or directory not found.

Many thanks
J

 

[JonSnell Electronic]

Do you mean C70/71&72?
If so the value is of little importance and are there to give phase shift for the motor determining the direction of rotation. If they are not short circuit, I would leave them alone.
Diodes D1/2/3&4? 1n4003 would suit well if you have short circuit diodes, which I doubt.

 

[jascha]

Thanks for reply. They are fine so far as I know but was questioning if they were worth replacing once I have the machine stripped.

One other question.... I want to clean the old grease from the capstan motors and relubricate it however I can’t find the right tool to take off the 4 studs. What can one use or any tips of what the tool should look like please? It’s not easy to grip the nuts to undo them.

Thanks
J

 

[Kay Pirinha]

These appear to be standard hexagonals. So I'd try the suitable socket from my set of spanners.
Best regards!

 

[ralphfcooke]

You'll probably need a tube spanner, most sockets aren't deep enough.
A possibility is a ring spanner, but it would have to be very thin.

 

[blinker]

To remove those bolts, I modified an 8mm deep socket. The socket is too thick to fit in the recess, so you need to thin the wall. Easy if you have a lathe. If not, spin it with a drill and file down the end of the socket to make it thin enough to fit.

Be careful when you rebuild the motor and don't overtighten those bolts. They snap very easily. I had to fasion a new one from threaded rod and a couple nuts.

 

[jascha]

Thanks for the tips. I did think of thinning down a hex drive however I did not try on a lathe as I would have thought that it’s hardened steel and would be a tough job. I was lucky that I managed to ease 2 of them with flat nose pliers at the end... originally I was attempting to carefully undo them by holding them with a grip vice from the thread by applying gentle pressure but was afraid that they would snap.

After I took then off I could see that one could replicate it then with a threaded rod and a nut! I just can’t understand why it’s been manufactured in such a way to complicate matter when it comes to servicing them!

Cheers

 

[Mark Tillotson]

Run caps, unless they've failed, should be fine, they are film caps. The value _is_ important,
as the two windings need be matched for current and in the right phase relationship for good
efficiency and low vibration. Too much current due to over-valued run cap can overheat a winding and burn out the motor.

 

[jascha]

Thanks for the technical useful info. I have fitted exact replacements as even though they might last for a while, the originals are bound to fail and it’s a pain to get to them and do a proper job. I replaced them with just modern equivalents and they work just fine. I feel relieved that I did this job so I don’t have to worry about them for some time.
Cheers