Revox B 795

[guiller]

Bonjour!
I'd use a less "reactive" cart myself like a better moving magnet or moving iron type with a user replacable stylus, perhaps one of the Ortofons. A moving coil cart puts a lot of sonic energy into an undamped light-weight support system and the REVOX cartridge carrier isn't designed to deal with it like a rigid and somewhat massive more conventional arm. There is also the issue of having to replace the entire cart instead of a simple plug-in stylus assembly.
I use an Ortofon MC in a lo-mass Souther linear radial arm, but I have modified it and it is damped against parasidic resonances. It is also relatively simple to change it out for another identical cart, a little less so for a different model.

The point is that I don't like at all the sound of MM for classical music (tried several good to very good ones, and the cheapest LOMC blew them up in terms of reproducing acoustic instruments and voices without amplification the way I know they sound) ! To me, a MM is out of the game for starting. If that TT would not accept a LOMC, then I will repair and sell it. From what you said, the effective mass of this TT is low, and I should look for a high compliance LOMC, if there is any out there (at least new, perhaps older models could fit the bill). It looks like a bad start then....

 

[steerpike2]

Maybe one of the Technics P-mount MCs?

 

[guiller]

Perhaps....The point is that this is a big delusion for me , as I wanted to go up the stairs, and not down. I've got a Thorens TD-126 Mk2 with a Yamaha MC-7 LOMC cart, and was thinking of getting a much better cart (like the Benz Micro Ace) for the Thorens. That would be a step forward. Then this Revox appearead, I had to decide quickly and thought that being a tangential TT I had the potential of avoiding inner groove distorion. Now I see that the Revox can only accept cartridges that are not among my expectations of finally having a really good one. I don't know, I feel I did a big mistake on the hurry. Now I am bound to buy something that I don't really like, but of course, it is my fault. Too bad to end 2009 like this. All the best

 

[SaSi]

I don't agree that the Revox TTs can only take MM carts. Yes, I agree that replacing the cartridge is not as easy as with a conventional arm, but it doesn't really take more than 10 minutes. Only strange thing that needs to be done is remove the platter and rest the TT upside down.

I have a B791 with an Ortofon MC20 MkII cartridge and an Ortofon T30 step up transormer. The combination really sings. The B791 was my first TT purchase in years and the sound really made me return to vinyl.

And the MC20 made me "discard" MM carts as (sorry to say) inferior. At least the ones I have and tried.

 

[guiller]

I don't agree that the Revox TTs can only take MM carts. Yes, I agree that replacing the cartridge is not as easy as with a conventional arm, but it doesn't really take more than 10 minutes. Only strange thing that needs to be done is remove the platter and rest the TT upside down.

I have a B791 with an Ortofon MC20 MkII cartridge and an Ortofon T30 step up transormer. The combination really sings. The B791 was my first TT purchase in years and the sound really made me return to vinyl.

And the MC20 made me "discard" MM carts as (sorry to say) inferior. At least the ones I have and tried.

This is great news to me! The Ortofon MC20 is definitely the kind of cart I could consider. Many thanks for sharing the data, SaSi. I'll put my best effort trying to fix the TT and look for the Ortofon cart. Happy New Year!

 

[Pio1980]

If someone has successfully used an MC in the Linatrack, good.
I'm using an O'fon MC-3 HO in the Souther SLA, it should work if not ideally in another lo-mass set-up.
The worst that could happen is that you don't like the sound of the combo and you keep the cart and sell a refurb'ed and running Linatrack. The best that can happen is total satisfaction.

 

[SaSi]

If someone has successfully used an MC in the Linatrack, good.

It is true that MC carts "require" high mass tonearms and high compliance MM carts require low mass tonearms. It is also true that the miniscule tonearm on the linatrak is perhaps the definition of low mass. But the combo is something that needs to be listened to.

 

[boyerd001]

For the Linatrack lovers among us who are told how bad it is to have a low mass and short tonearm, you might want to go over to Simon Yorke's website and check out his new "Aeroarm". Seems he doesn't have a problem with low mass and short tonearms!!

Gee, I wonder if he sells them for less than a couple 2-3 thousand Euros (yeah right!)?

Also, for the last few posters with newly acquired Revox TTs, go over to the Studer FTP site and download the B791/795 Service Manual - all the setup info you need is in it.

ftp://ftp.studer.ch/Public/Products/Revox/Revox_B791-B795/

By the way, you don't need the "Alignment Gauge" that Revox use to sell to properly set up the table's tangential tracking. Use an old record with a radial mark (as mentioned earlier) AND use the adjustable eccentric in the Linatrack's pivoting base to fine tune the stylus's alignment. This approach removes the 10mm stylus tip to mounting hole dimension that the alignment gauge limits you to. The Service Manual shows you the eccentric's location and how it's adjusted. Also search out a previous post I made to SaSi on how to tell - with the tonearm is resting on a record - if the "spacers" being used with the cartridge are of the appropriate thickness.

Dale

 

[Robie]

Guiller: Good luck with your B795. FWIW, I have a older "low mileage" Grado 8MR MM cartridge on mine. When the TT was working previously, I was surprised at the weight of the low frequencies this MM cartridge produced even though the TT was beset with lots of Wow making it unlistenable. BTW, I am a LOMC fan myself and use a Denon DL103 on my Rega Planar 2.

My B795: Since Mark is tied up with other repairs, I have contacted one additional site (o2xygen.com) as well as Siemens directly regarding obtaining two Siemens SBV566 Hall Sensors. o2xygen.com's site seems to suggest that they have 91 of them available. Not sure if Siemens will be able to assist given the fact that the SBV566 is no longer in production.

 

[markthefixer]

Have we eyeballed the sensors in the Revox to figure out who made them?

As opposed to "rolling our own"?

What works out better for you in general Robie, weekdays or weekends?

I did find some appropriate sensors in surface mount devices.. at under 2 bucks each...

 

[Robie]

Have we eyeballed the sensors in the Revox to figure out who made them?

As opposed to "rolling our own"?

What works out better for you in general Robie, weekdays or weekends?

I did find some appropriate sensors in surface mount devices.. at under 2 bucks each...

I thought Steerpike ID'd them as most likely the Siemens SBV566. I'll let you know if I hear anything regarding acquiring two of them. Not holding my breath.

I'm wide open for the next week or so, Mark.

 

[guiller]

Guiller: Good luck with your B795. FWIW, I have a older "low mileage" Grado 8MR MM cartridge on mine. When the TT was working previously, I was surprised at the weight of the low frequencies this MM cartridge produced even though the TT was beset with lots of Wow making it unlistenable. BTW, I am a LOMC fan myself and use a Denon DL103 on my Rega Planar 2.

Thanks for the data Robie: I've got the Revox yesterday, but didn't have time to open it. I'm planning to replace the caps and then see how well it behaves. If I succeed in having it back into operating condition I'll come back later to the cart issue. I'm crossing my fingers. Hope to post some pictures of the inside soon.

 

[steerpike2]

ReVox didn't publish the Hall device "OEM" details because you are/were supposed to order them from Studer, where they would have been tested and categorised into matched narrow-spec devices.

Actually they didn't want people replacing them at all, because the alignment was quite trickey - they preferred replacement of the complete, fully aligned motor which would guarrantee correct performance.
Generally they would take back an assembly like a faulty motor with a corresponding discount on the new part, and re-furbish that part, but not anymore for something out of production like a B795 motor. (and Studer/Revox kinda fell apart after it was sold to Motor Columbus)

 

[Pio1980]

For the Linatrack lovers among us who are told how bad it is to have a low mass and short tonearm, you might want to go over to Simon Yorke's website and check out his new "Aeroarm". Seems he doesn't have a problem with low mass and short tonearms!!
--SNIP--
Dale

Well, he wouldn't, he's emotionally bonded to his brainchild (who isn't?). It's a good concept in theory but needs a perfectly flat record and on-the-fly VTA/VRA adjustment for anything like "High-End" performance.
This is essentially the same as the excellent VERSA Dynamics set-up mentioned in another linear tracking thread, but without the vacuum platter that assures proper fixed geometry. Both of these examples are much more rigid than the REVOX carrier and the gantry is simpler with fewer resonant-prone elements.
The REVOX like the B&O is an ingenious well engineered and well made record playing system with a somewhat different approach. Neither is perfect and they are prioritized differently. I like heavy platters with dead heavy mats on quartz-locked direct-drive motors for their pitch-perfect steady speed control and vibrational "grounding" of the disk in play. The B&O tables have light belt-driven platters with no mat. The REVOX carrier's ultra-short pivot-to tip arrangement magnifies any VTA/VRA variation/error, the integrated B&O arm is much better in this regard but has a more complex pivot bearing arrangement. The REVOX carrier has (theoretically) no free play possible in it's unipivot. Both have lots of resonant rattly bits around the pick-up carriers (like my beloved and modified Souther). And so on----. Neither is perfect or "High-End", but they are acceptable record playing systems in their own ways.

Postscript; The dead B-790 I was haggling has apparently evaporated into cyberspace along with it's seller, have had no FB for my 2 follow-up messages. Looks like I won't get to play with one of my own after all. I'll commiserate with a Pioneer PL-L1000 sometime later in the year when it shows up.
Regardless, it's comforting to know the depth of support available here if I do come into a Linatrack.

 

[koseltri]

Well, he wouldn't, he's emotionally bonded to his brainchild (who isn't?). It's a good concept in theory but needs a perfectly flat record and on-the-fly VTA/VRA adjustment for anything like "High-End" performance.
This is essentially the same as the excellent VERSA Dynamics set-up mentioned in another linear tracking thread, but without the vacuum platter that assures proper fixed geometry. Both of these examples are much more rigid than the REVOX carrier and the gantry is simpler with fewer resonant-prone elements.
The REVOX like the B&O is an ingenious well engineered and well made record playing system with a somewhat different approach. Neither is perfect and they are prioritized differently. I like heavy platters with dead heavy mats on quartz-locked direct-drive motors for their pitch-perfect steady speed control and vibrational "grounding" of the disk in play. The B&O tables have light belt-driven platters with no mat. The REVOX carrier's ultra-short pivot-to tip arrangement magnifies any VTA/VRA variation/error, the integrated B&O arm is much better in this regard but has a more complex pivot bearing arrangement. The REVOX carrier has (theoretically) no free play possible in it's unipivot. Both have lots of resonant rattly bits around the pick-up carriers (like my beloved and modified Souther). And so on----. Neither is perfect or "High-End", but they are acceptable record playing systems in their own ways.

Postscript; The dead B-760 I was haggling has apparently evaporated into cyberspace along with it's seller, have had no FB for my 2 follow-up messages. Looks like I won't get to play with one of my own after all. I'll commiserate with a Pioneer PL-L1000 sometime later in the year when it shows up.
Regardless, it's comforting to know the depth of support available here if I do come into a Linatrack.

You'll have plenty of support for a PL-L1000 also. I'm going to snag a Revox too if the opportunity arises.

 

[guiller]

Hi,

I finally bought the B795. I opened it up. All boards seem to be there (according to the Service manual). The TT has been opened and "serviced" before, unfortunately:

General view:



I guess the space prepared for a board in the rear right is not used by a missing board, right?

Motor Control PCB



This board has been modified. There is a IC on top left that has been replaced. Some transistors look bad and seem to have been replaced too.

Tone arm control PCB



Looks OK

Power Supply PCB



Looks OK

Connectors from the Motor board:




There is one male pin missing, however that missing part is in the female connector. There are a couple of other multi-pin connectors in this shape. What do you people do to deal with this?

I will start by replacing the 5 gold electrolytic caps, and then try to see what happens. According to the seller, the TT had "speed issues". No wonder, somebody did something on the Motor Control PCB.

I will be asking for help on this. Hope you guys give me a hand in my effort to resurrect this beautiful TT!

All the best

 

[henkuk]

Motorboard, the pin missing is how it is supposed to be. As you can judge, on the left hand side it has only two wires, then the missing pin which is filled on the female side with a blanking pin.

They produced them like this so you don't attempt plugging it in the other way round.
My B790 is identical in that so you put that one to bed.....

 

[Pio1980]

Thnx for the wonderfully useful images!
Lotta work done there, one wonders what for. Shoulda changed out the yellow Frako e'lytics first, then the rest. Looks like it's mostly there, I think those motor board drive transistors are supposed to be on a heatsink. It looks worse than it probably is, the work was somewhat clumsy but purposeful. Nothing that can't be tidied up or redone.
Here's a photo of the interior of another B-795. Apologies to the unknown owner/poster.

 

[henkuk]

BTW here is a photo of the inside of my B790 just so you can compare.

 

[guiller]

Thanks guys! As I mentioned, I'll start by replacing the Frako caps, and then address the Motor Control PCB. I'll keep my fingers crossed and ask for help when I get to that phase.