ReVox B790 crazy

[beolit]

Merry Christmas everyone!

I need a help about problem.

I have a Revox b790 and I have a problem with a control system cartridge.
On start playing all is good, passed a 3/4 minutes the play, the cartridge system goes up for himself, then i lost the button control to down other time, the system no works more. When pressed the button to raise or lower the cartridge (lowering/lifting), not respond.
at next day, the same, it works good only for firsts minutes.

May be a IC control?

I would appreciate some guidance on someone with experience in this problem.

I dispose of the manual and tools to try to fix it.

Thank you very much and happy new year.: Prost:

[borchee]

AW: ReVox B790 crazy

Hi,

it might be an IC failure, altough unlikelly - working/not working at will.

The common problem on the tonearm control board is (amongs bad/old capacitors) the contact between IC-legs and IC-socket - so, check it.

Pull out an IC - you'll probably see that the legs are black (silversulfide), what very likely might be the cause of poor contact. Jiggling the ICs in the sockets may temporarily solve the problem, cleaning the legs would be the way to go though.

Strangely, it is recommended to change all IC-sockets, altough they don't really suffer from corrosion/oxidation. I had a problem with a socket which was to loose - gripping the IC-legs I mean...had to change it.

Replacing all the capacitors should be done, also rejuvanating the power supply PCB, cleaning the tonearm guiding rails and the tonearm transport cord (with acetone - as recommended by SM - to reassure grip).

Also inspect the RTs on the power supply board for cracks and don't forget to replace the RIFA.

Good luck
Borut

[Blockbusters]

Re: ReVox B790 crazy

@beolit,
As borchee allready say, could be a problem on the tonearm control. If you want to make sure to solve this, this link will be usefull.


@http://www.ebay.de/itm/Reparatursatz-Revisionssatz-fur-Revox-B790-Tonarm-Steuerung-Neuware-/181256592391?hash=item2a33bc1c07:g:LNwAAOSw~gRVzE0 B

Meine Revox Geräte:
B790, B215 mk2, B250, B225, B205
B291, B215 mk1, B285, A725, A727, A721. B208
Equipment is upgraded with Jensen and Duelund and Panasonic FC capacitors and Burr Brown opamps.
Revox is poisonous. Once you listen to it, Everything else become abnormal sounding.

[beolit]

AW: ReVox B790 crazy

Hallo,
Many thanks for the value info!
I'm gonna try...
Cheers

[beolit]

my b 790n still crazy

Hey there

A few weeks ago started a post about a problem in my b 790.

The problem still persists and the theme here ...

After following the advice to clean all connections IC, capacitors have also replaced the power supply.

Also cleaned the rails.

The problem follows:

All is well when I turn on the B790 and ordered Play, this works for 2-3 minutes, then the head is disconnected and goes to stand by its position and not fall more.
When I turn off the system for a few minutes, the same happens again render sequence, so again and again, or without turning off the system, wait 3-4 minutes and again otos run for 2-3 minutes, no more.

I've noticed that when giving the ruling, sounds like triggers the relay, and I give the order to lower "play" not the relay is heard.

You can then replace the relay?

No where to go ....

Many thanks!

[beolit]

AW: ReVox B790 crazy

The problem still persists and the theme here ...

After following the advice to clean all connections IC, capacitors have also replaced the power supply.

Also cleaned the rails.

The problem follows:

All is well when I turn on the B790 and ordered Play, this works for 2-3 minutes, then the head is disconnected and goes to stand by its position and not fall more.
When I turn off the system for a few minutes, the same happens again render sequence, so again and again, or without turning off the system, wait 3-4 minutes and again otos run for 2-3 minutes, no more.

I've noticed that when giving the ruling, sounds like triggers the relay, and I give the order to lower "play" not the relay is heard.

You can then replace the relay?

No where to go ....

Many thanks!

[borchee]

AW: ReVox B790 crazy

Hi,

regarding your question per PM...I'll rather answer it here, because it may trigger more response from experts.

So...unfortunatelly, my "knowledge" consist only of reading and having the balls to tackle the problems, especially the mechanical ones, by myself - I have absolutely no clue about electronics, nor the equipment (just a multimeter) to troubleshoot reasonably.

Well, I am usually able to locate the problematic PCB, a connector or similar, but this is mainly due to interchanging the pieces between identical devices. Finding which element is faulty is another story.

You should replace all capacitors (they're junk after 30+ years anyway), not just the power supply ones and then see if the problem remains.

Regards
Borut

[steerpike]

AW: my b 790n still crazy

I had a similar problem in one of mine:
The microswitch that detects when the arm is at its end-point was faulty, and giving a false activation signal.

[beolit]

AW: ReVox B790 crazy

Hi mate!

I have also checked the limit run switch, is well the collected at the time.
Thanks for the tips, it is true that I have replace electrolytic capacitors, but not a tantalum caps, that'll have to do now.

Cherrs!