Hi Charlie,
Congratulations on your purchase of the high speed Revox G36. I have two G36's, both normal speed. I also overhauled an F36 which I have given to a friend. The same friend and I also have one high-speed B77 each. The B77 is a smoother machine in both operation and sound, but the 36 series machines have a very dynamic and lifelike sound. We suspect it's the valve electronics.
It's very important to determine that you have an original high-speed G36 and not a modification, as a modification, made by changing the capstan shaft only, results in an incorrect tape path. The correct way to make a modification was to change both the capstan shaft and motor, but back in the days when both parts weer available the combined cost was more than the secondhand value of the whole deck so nobody bothered, they just changed the shaft which got the speed right and ignored the change in the tape path geometry.
All original high-speed G36's were Series III machines, so they should have a photoelectric tape end switch, not the mechanical switches of the earlier Series I and Series II machines. A mechanical tape end switch would mean it's a modification. Also, look at the speed selection pushbutton markings on the front panel. Are they printed directly on the aluminium insert or are they on a sticker? I think the original factory high-speed machines had the speeds printed directly on the aluminium but I am not sure, perhaps some of the factory machines had a sticker with 7 1/2 and 15 taped on top of the normal 3 3/4 and 7 1/2 markings.
Get yourself a good demagnitiser as the tape lifters and the guide flanges are ferromagnetic and if they become magnetised they could damage your tapes. And of course the heads will also benefit from regular demagnetisation. The Han-D-Mag by
R.B. Annis is a good choice.
Also check that you have the new pattern heads as the old type heads don't last nearly as long and don't have as wide a frequency response. The new pattern heads have integral head shields shaped like those on the heads on more modern Revoxes like the B77. The old pattern heads have cylindrical shielding cans which are separate from the heads. The new pattern heads are, basically, identical to the heads in the B77 and PR99 so they are as good as any heads fitted to any semi-pro machine.
The only rubber parts a G36 could possibly ever need attention to are the pinch roller and the decoupling strips between capstan motor and flywheel. I don't know if those are still available. If they are I would get them to have in stock if I were you.
G36's in "as found" condition today often suffer from lack of lubrication to the capstan shaft and to the capstan motor bearings. Especially the motor bearings were supposed to be lubricated for life, but I suspect at the time the Revox engineers designed these, they never considered some of them would still be in use over forty years later! This sometimes causes the capstan motor not to come up to speed, or to "hunt", especially at the higher of the two speeds. Dismantling and lubricating the capstan bearing and motor prevents this. You might also find that old molybdenum grease has become sticky and is causing the three solenoids (pinch roller, brakes, and push button release) to stick. Cleaning and lubricating the solenoid bores and slugs takes care of that. With this, and a little attention to the brakes perhaps, the mechanicals of the G36 are good for another 20 years. That really is a low maintenance transport.
You might find recordings made on the G36 sound bright, no matter what you do to the bias. This is because the recording circuits on earlier G36's were tuned to the tape formulations available in the early 1960's. By the end of the 1960's the frequency response of studio tapes began to approach what we are familiar with today, and they didn't need as much treble boost as earlier tapes. Revox made a small modification to the record amplifier pre-emphasis circuit at some point, to bring the machine in line with tapes becoming available at the time. It is easy to make the same modification to those machines that haven't had it from the factory. Indeed, the tape used by The Tape Project, which also happens to be my favourite tape, Agfa PEM468 (today's RMGI SM468) first became available in 1971, at about the same time as the G36 was going out of production. In fact the G36 works very well with this tape when the record amps have the frequency response modification and the bias is tuned for it. I use a reference fluxivity of 355 nanowebers per metre. I set the VU meters to read 0dB at this level, and set bias for a 4dB drop-off at 10kHz.
Of course, if you're going to be using the machine mostly for playback, you don't care much about the bias, recoring eq, and reference level. If that is what you are going to be doing, then choose three nice ECC83/12AX7 valves for the playback circuit and leave some old valves in the rest of the circuits. There are another two ECC83/12AX7, two ECL82/6BM8 and one ECC82/12AU7 in the rest of the circuit and it would be a pity to fit new ones and have them just wear out while you're only using the playback circuits. Whatever you do, though, do leave all the valves in position as removing them changes the supply voltages and that is not good news.
I hope you found the above useful. Let me know how you get on with your G36 and if you have any questions at all, don't hesitate to ask.
