Revox G36 Motor caps advice please

[DMcMahon]

Just realised from post # 3 that the photos above are most likely showing the spooling motors capacitors where as you say 0.5uF has been added in parallel to the 3.0uF to make 3.5uF

Still leaves a question of whether you have the 0.5uF C70b connected to one end of the capstan motor 2uF C70a.

[jascha]

Thanks for your reply. I can say that the photos above that I attached a few days ago are of the spooling motor caps and not the capstan motor one.
The spooling motor cans have a 0.5uf strapped in parallel to them so that is I guess understood that the total capacitance for those motors is 3.5uf and as a result I have bought a new set that are 2 pin caps.

I just checked again the capstan cap and I confirm that pin 3 is N/C. There is no measurement whatsoever to the other pins...completely open. I measured the capacitance across pin 1 & 2 and it's measuring just 1.7uf so it's time to replace those caps i think.
I think the schematic you referred to is of a series 3 and my machine is a series 2. I attach a section of the schematic where some machines just use a 2uf cap.

Hope this is making some sense?

Thanks

[DMcMahon]

Yes makes full sense now. I was incorrectly thinking it was a Mk.3/Series 3, you had a few posts earlier confirmed it was Mk. 2

[jascha]

That’s no problem at all and thanks you for all your time and effort to help. Much appreciated

[Welsh Anorak]

You mention it's a high speed version, likely done by Revox. I have an HS version as well and I was wondering what the 7.5/15 ips lettering is like - mine has stickers over the original standard speed lettering, and I wondered if this is original or a later conversion.

[jascha]

Mine has also a sticker on top of the original speed letterings of 3.75 & 7.5 ips. I believe it was done by Revox as I heard that they had made these modifications themselves. I heard from a knowledgable person that’s how I know but that’s all I know.

[Ted Kendall]

High speed G36s are a variable feast. I think the first were converted by Hammonds, who were the importers at the time. This was a simple matter of doubling the capstan diameter on the standard 6/12 pole motor, although one I briefly owned had an E36 motor with a bigger capstan fitted, an ran 1% slow...

The problem with this arrangement was that it affected the wrap on the play head and took the tape path out of the height-setting guide, making alignment very touchy. When Revox themselves made a high speed G36, the first machines had a 4/8 pole capstan motor. thus only requiring a 50% increase in capstan diameter and bringing the wrap within bounds. This was later supplanted by a large diameter capstan in a new casting which set the motor, and hence the capstan face, back about 2mm.

Factory high speed machines seem to be much rarer than Hammond conversions, in the UK at least. When I rebuilt two G36s a few decades ago, I bought new high speed deck covers from Bauch, and these had no labelling on the speed buttions - the inference being, I suppose, that a professional would know what speed he was running at. The likelihood, therefore, is that a machine with sticky labels on is a conversion. Much the same applies to A77s - anything proclaiming itself "professionelle Apparat" isn't...

[TIMTAPE]

From memory another thing about the Revox G36 was a rubber coupling between motor and flywheel/capstan. Apparently it smoothed flutter. I wonder how the compliance of that rubber coupling has stood up over many years.

A couple of years ago I was offered a G36 in very good cosmetic condition, one owner since showroom new in 1967. I think that was the year the new A77 came out. Having had no experience with them I was amazed at how difficult the G36 was to work on re the A77 which had replaced it. The design went from valves and tag strips on the G36 to silicon transistors on mostly separate plug-in PCB's on the A77. Also the A77's capstan motor changed to an electronically controlled AC type with great immunity to mains irregularities and with the possibility at least of electronic varispeed, exploited on later B77's. The rubber coupling was no longer necessary.

This G36 while cared for cosmetically had had a lot of tape through it. The heads were quite worn and the capstan shaft had a tape sized wear groove in it, reducing its diameter and therefore the tape speed. Unlike an electronically controlled design, no adjustment of motor speed to correct this was possible. It was at that point that I decided to pass the machine on...