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Old 13th Jul 2019, 12:07 am   #12
MeerKat
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Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
Posts: 296
Default Re: Revox A77 refurbishment advice please.

Evening All (now who said that?)

Lets put the question of hours run to bed, I don't want it to become a distraction from the original reason for starting the thread! I'm with you on the Rifas Ted. See attached picture of the play head, I can see little, if any wear hence my reason for saying low hours, nuff said, lets move on!

I have checked the counter and I do only have the one belt. BTW the wind motors are marked 2/76 so this must be a late model as production was from 67 to 77, S/N is G2050XX, why I have the earlier counter I don't know, maybe supply problems? Anyhow just a simple 'O' ring belt required.

Thanks for your confirmation David about the components to replace, and to you Michael for your tips, Nichicon caps came to my mind as well. I'll build a list of what I'll need.

Anybody have recommendations on the trimmers?

Now the brakes again, mine seem to be a hard cream coloured plastic bonded all round onto the drum, if they are cotton tape it's impregnated with something that when you gently run a a scapel over them gives the impression of a hard rough surface, is this normal? I'll clean them with acetone and see if that softens them any, thanks for that tip Ted.

Alignment – I have a scope and meters, nothing else suitable so I plan to do one board at a time making sure not to mix up CH1 & CH2 ones. I will carefully measure and record the resistances of the trimmers before removal and set the replacements to the same once there installed. This will be easy for some e.g. the four on the oscillator board but not so easy for others e.g. P501/P502 on the record amp boards, in these cases I'll need to record the resistances from each end of the pot to the wipers, noting which way round the meter is so diode/transistors junctions don't mess things up. I know this will not restore everything to exact pre-replacement values, I'll have to put an ask out for somebody with the right gear that would be happy for me to visit with my machine and do the final tweaking.
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