Revox B790 Tangential Tonearm or spares?

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JimmyB
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Revox B790 Tangential Tonearm or spares?

Post by JimmyB » 10 Feb 2019 23:30

Wonder if anyone can Help with finding either a working Revox B790 tonearm or one I can use for spares. Mine has a lift problem (bit more than that as it's missing the lift bar and so I'm guessing the lift thingy has also got a problem).

Tonearms from B791/795 and 291 will work as well to my understanding.

There's actually one on a Norwegian site but as it says it's Norway only it's a bit out of reach.

Thanks,

J

borchee
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Re: Revox B790 Tangential Tonearm or spares?

Post by borchee » 11 Feb 2019 18:08

My suggestion(s):
- download the service manual for B795/791 (exploded view of the tonearm)
- check with your tonearm what's missing
- post some pics.

Spare parts may still be available from Revox (not Studer!)...there's a B795/791 tonearm offered at ebay France (from Belgium, actually).
...BUT!...if you're missing just the lifting rod...it's simply a piece of square aluminum 3x3mm (check the lenght yourself...cca. 185mm).

B

JimmyB
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Re: Revox B790 Tangential Tonearm or spares?

Post by JimmyB » 12 Feb 2019 22:34

Thanks for that, must have missed the French arm, will have a look...

https://m.imgur.com/a/E6olsb9

From the image I've got, (if it shows) it looks like the rubber boot is missing but possibly the lifter arm is there and for some reason the 3mm bar is missing.

To take this apart to lose the bar, I'm guessing there was a reason which I need to fix....

Thanks for the dimensions though, think I have some brass bar of 3mm square I can just try...

borchee
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Re: Revox B790 Tangential Tonearm or spares?

Post by borchee » 13 Feb 2019 18:21

OK...

If the picture is of yours TT, it is an early one (state the serial number - not the one on the tonearm, but the one on the chassis).

Difference(s), I know of, early to late SN:
1a) early SN...the two round guiding rods are coated with teflon (not absolutely sure, if it's teflon, but coated they are)
1b) late(r) SN...the two round guiding rods are chromed?/shinny

2a) early SN...the two arms holding the square lifting rod/bar are a two-piece part (upper and lower part, screwed together...or in that fashion, if I remember correctly)
2b) late(r) SN...the two arms are made as one piece

There are more, but not relevant at the moment.

What's obviously missing:
- the lifting rod
- the two arms (plastic) holding it.

Remove the side cover and post some pics of the solenoid to see, if there's something else missing.

There's not necesseraly something wrong with the tonearm besides the missing parts - it has been reported about broken lifting bar arms...due to owner/tech stupidity, though. Probably the tonearm wasn't even disassembled; just the arm and bar removed, for whatever reason, and then got missed in action.

Measure the diameter of the guiding rods...the arms can be quite easy to DIY...or contact Revox.

If with "rubber boot" you mean the dampening rubber bellows:
- AFAIK all of B790s were originaly equiped with it...black or white ones
- the piston damper may indicate that the TT was serviced at a Revox service.

Regarding brass bar...being multiple times denser/heavier than aluminum, it would likely cause problems with the rubber bellows (no way to regulate air flow but to seal it to some extend to eliminate a to high speed of the tonearm lovering...fiddly to do, altough possible)...but, it may function just well with the piston damper. Naimly, on the bottom of the piston is a small hole and by turning the piston (clockwise or anti-clockwise doesn't matter) the hole gets covered (partially, full, not at all) by the plate holding the piston, hence air flow/lovering speed is regulated.

Once again!!: check with the service manual to find out which parts you're missing...and post some photos.

B

PS: BTW, don't even think about DIY-ing the arms in such a hideous way! :toilet:
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