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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 22nd Feb 2024, 10:05 pm   #1
Michael Maurice
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Default Revox A77, potentiometers

I’m referring to the input level, balance and volume controls.

These are no longer available from the manufacturer and they are totally non standard.

Someone is selling an ALPS version on eBay but at just over £85 it is very expensive.

Apart from a second hand one if you can find one, has anyone any ideas as to how to get around the problem?
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Old 23rd Feb 2024, 11:17 am   #2
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Default Re: Revox A77, potentiometers

Hi Michael
I have a VERY scrap A77 here. I've removed the controls. They all have slightly bent shafts and one of the input level controls has seized solid, but they're yours if you need them.
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Old 23rd Feb 2024, 1:12 pm   #3
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Default Re: Revox A77, potentiometers

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Hi Michael
I have a VERY scrap A77 here. I've removed the controls. They all have slightly bent shafts and one of the input level controls has seized solid, but they're yours if you need them.
Yes please
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Old 23rd Feb 2024, 3:47 pm   #4
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Default Re: Revox A77, potentiometers

PM sent.
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Old 23rd Feb 2024, 6:35 pm   #5
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Default Re: Revox A77, potentiometers

It seems the usual suggestion for anything potentiometer related is to talk to Blore Edwards. I imagine you have long experience with the machines, so if these things are commonly wanted perhaps even getting a minimum order manufactured would be worthwhile? What do the Revox spares firms do?
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Old 23rd Feb 2024, 8:28 pm   #6
Michael Maurice
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Default Re: Revox A77, potentiometers

I've tried Blore Edwards, they don't have anything suitable, I may explore a method using Piher potentiometers, make up brackets, a coupler, a suitable shaft and a PCB.

I would prefer to use a 16mm pot rather than the usual 24mm. Space is quite limited.
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Old 24th Feb 2024, 1:27 am   #7
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Default Re: Revox A77, potentiometers

Michael what are the problems with the pots you are encountering?
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Old 24th Feb 2024, 11:14 am   #8
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Default Re: Revox A77, potentiometers

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Michael what are the problems with the pots you are encountering?
Very intermittent contact on CH2, not curable with switch cleaner. mainly no go as though the contact on the slider has failed.

I haven't opened it up, this is a professional repair for a customer.
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Old 24th Feb 2024, 1:25 pm   #9
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Default Re: Revox A77, potentiometers

Nagravox?…..
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Old 24th Feb 2024, 2:14 pm   #10
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Default Re: Revox A77, potentiometers

Quote:
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Quote:
Originally Posted by TIMTAPE View Post
Michael what are the problems with the pots you are encountering?
Very intermittent contact on CH2, not curable with switch cleaner. mainly no go as though the contact on the slider has failed.

I haven't opened it up, this is a professional repair for a customer.
On some cases of badly tarnished contacts I find the spray switch cleaner I use evaporates too quickly to do much. I sometimes soak a tarnished part in a mildly acidic bath like vinegar for a few hours. If the problem cant be fixed any other way, there's nothing to lose.

I did this recently on the long B77 speed and EQ change switch. The many contacts had tarnished badly apparently due to a combination of much accumulated dust and moisture. The contacts came up well.
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Old 26th Feb 2024, 5:29 pm   #11
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Default Re: Revox A77, potentiometers

I guessed you'd probably already been in touch with B.E. Are they not able to make ones to spec? Perhaps they're too peculiar in casing or construction to be able to copy on their machinery.
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Old 27th Feb 2024, 10:03 pm   #12
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Default Re: Revox A77, potentiometers

The only ones they can do is AR45 24mm ones, not 16mm. I would have to get brackets made up anyway but the 24mm ones are quite large compared with the originals. I made enquire from Piher.
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Old 27th Feb 2024, 10:16 pm   #13
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Default Re: Revox A77, potentiometers

Are these pots the type with a diecast metal case held together with small rivets? I ask because many years ago I replaced the carbon track with the track taken from a preset. The rivets were carefully drilled just enough to be able to punch them out and they were reused with a tiny amount of araldite to keep them in place. It was on a tape recorder and had a long shaft but I don’t remember which type, although it wasn’t a Revox.
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Old 27th Feb 2024, 10:18 pm   #14
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Default Re: Revox A77, potentiometers

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Are these pots the type with a diecast metal case held together with small rivets? I ask because many years ago I replaced the carbon track with the track taken from a preset. The rivets were carefully drilled just enough to be able to punch them out and they were reused with a tiny amount of araldite to keep them in place. It was on a tape recorder and had a long shaft but I don’t remember which type, although it wasn’t a Revox.
Interesting, yes the are this type, I’ll have a try at doing this, though I’ve now got a replacement pot.
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