Author Topic: Revox A77 help,please  (Read 473 times)

Offline marcochezzi

Revox A77 help,please
« on: April 24, 2019, 05:49:17 AM »
Hello fellow Forumites. I came across a Local owner of a Revox A77 on Facebook who needs help with his machine. Seems the unit will only rewind or play when the buttons themselves are held in, let them go and the machine stops. There seems to be some feedback on Facebook regarding the optical sensor globe being gone, or failure of the sensor itself which seems easy enough to bypass should the sensor be no longer available, globes are an obviously easy replacement. Anyone here that knows of this fault, I would really like to help another fellow RTR owner out if possible..

Offline christempler

Re: Revox A77 help,please
« Reply #1 on: April 24, 2019, 09:00:51 AM »
Hi,
Speak to Dewald at Dewaudio. He knows those machines very well.
07720395379

Chris
"Never try to teach a pig to sing. It wastes your time, and it annoys the pig." Robert Heinlein
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.
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Offline marcochezzi

Re: Revox A77 help,please
« Reply #2 on: April 24, 2019, 11:54:31 AM »
Hi,
Speak to Dewald at Dewaudio. He knows those machines very well.
07720395379

Chris

Thank you, will probably see the machine tomorrow and then contact Dewald if the obvious points nowhere... Kind Regards - Marco

Offline Steerpike

Re: Revox A77 help,please
« Reply #3 on: April 24, 2019, 02:08:55 PM »
If the lamp for the tape end sensor dies you do not get the symptoms you describe. What you get is a machine where the auto stop never  functions and it continues to try to play even the end of tape has run out.

The a77 requires that a dummy jumper plug be inserted into the remote control socket - check that such a plug is inserted,

 otherwise

Likely cause is failed frako brand capacitors on the tape drive control board. It is a universal problem with every revox product made since the 1970s

Offline marcochezzi

Re: Revox A77 help,please
« Reply #4 on: April 24, 2019, 04:04:06 PM »
If the lamp for the tape end sensor dies you do not get the symptoms you describe. What you get is a machine where the auto stop never  functions and it continues to try to play even the end of tape has run out.

The a77 requires that a dummy jumper plug be inserted into the remote control socket - check that such a plug is inserted,

 otherwise

Likely cause is failed frako brand capacitors on the tape drive control board. It is a universal problem with every revox product made since the 1970s

Yep, thank you Steerpike, I had an inkling in that direction as well, have done some research in that regard and yes the dummy jumper plug issue comes up often enough, I am lead to believe that often even if the dummy jumper plug is there then there is a good chance of poor electrical contact between the dummy plug & socket causing what seems like the same fault..

If that does not work I'll shorten all the springs, bend all the mechanical plates out of spec, oil the brake pads after re-tensioning the drive relays and realigning the heads by ear, cause' that is the way I used to receive equipment in the workshop after clients "had a go' fixing things themselves..., not forgetting to adjust all the internal pots, cause' they twist themselves out of spec....

Anyway, owner has a full schematic and I'm keen to give it 15 minutes, anything more and it goes to the pro's, I'm fully aware how sensitive those machines are cap and internal pot wise, don't want to land myself in any hot water I cannot get out of..

Offline marcochezzi

Re: Revox A77 help,please
« Reply #5 on: April 25, 2019, 05:21:02 PM »
Gents thanks to all for the feedback, Steerpike you were spot on, unit arrived at my home today with the missing dummy plug. Schematics show pin 1 & 2 (red & brown cable) being the short once the plug is installed, so as the owner said he has the plug at home, a simple wire bridge into the socked proved the machine working as it did out the factory...

Must admit I was surprised at first at just how small that machine is, and simple architecture inside, makes my 1500 look colossal by comparison. Anyway, quick visual shows the last 30 odd years in storage have not had any seemingly bad effect, however time will tell, owner needs to purchase new reels & tape and then the long term test begins.

Iíll be moving home in the next month or two so I told him that if he is willing to wait and bring it around again Iíll get around to a proper clean, both electrical and mechanical, plus lube wherever necessary once Iím done with the property thing, in the meantime he needs to sort out getting some reels and tape, not sure I want to get rid of any of mine just yet...





« Last Edit: April 25, 2019, 05:41:09 PM by marcochezzi »

Offline Family_Dog

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Re: Revox A77 help,please
« Reply #6 on: April 25, 2019, 05:29:23 PM »
Considering its age, that Revox is in excellent condition. Well worth complete restoration.


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Offline marcochezzi

Re: Revox A77 help,please
« Reply #7 on: April 25, 2019, 05:47:19 PM »
Considering its age, that Revox is in excellent condition. Well worth complete restoration.
-F_D


Agreed, dropped a little ďif you want to sell please keep me in mindĒ message, just maybe one day she will be mine..!!
« Last Edit: April 25, 2019, 05:56:10 PM by marcochezzi »

Offline fdlsys

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Re: Revox A77 help,please
« Reply #8 on: April 25, 2019, 08:26:13 PM »
Those golden colour translucent Rifa polyprop caps, there should be 5 of them - replace immediately with at least 250V or higher voltage X2 PP. Rifas will blow the stinky smoke, it's a given.
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
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Offline marcochezzi

Re: Revox A77 help,please
« Reply #9 on: April 27, 2019, 04:49:09 AM »
Those golden colour translucent Rifa polyprop caps, there should be 5 of them - replace immediately with at least 250V or higher voltage X2 PP. Rifas will blow the stinky smoke, it's a given.

Thanks for the info fdlsys, so those are the smokers then.. ok, will get around to the caps a few months from now, will keep posting as I go along..


Offline neilpainter

Re: Revox A77 help,please
« Reply #10 on: May 09, 2019, 10:33:23 PM »
Guys, I joined this forum yesterday and am blown away by the content and knowledge out there! Unbelievable! I hope I can jump in on this thread, I have a Teac X-1000M Reel Deck that has hardly ever been used and has been boxed in storage for 16 years so its beyond mint! It's in need of repair it powers on but nothing is working Hans Lemmerer who looked at it briefly (and was no help whatsoever) says it needs either a new motor or logic board and there is nothing he can do and dismissed it. Help!

Offline fdlsys

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Re: Revox A77 help,please
« Reply #11 on: May 10, 2019, 08:03:15 AM »
Talk to Bobby when you see him about the cassette decks.

Thumbsuck diagnosis :
If the machine was working before it was boxed for 16 years, typical suspects are the caps, perishables (rubber parts) and ceased bronze bushings.
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
Come back when youíve lived a little. Miles Davis

Offline Steerpike

Re: Revox A77 help,please
« Reply #12 on: May 10, 2019, 10:42:30 AM »
I have a Teac X-1000M Reel Deck that has hardly ever been used and has been boxed in storage for 16 years so its beyond mint! It's in need of repair it powers on but nothing is working

The "M" suffix is by far the best version of any X-series. Half track & 15 IPs. And quite uncommon.

Quote
Hans Lemmerer who looked at it briefly (and was no help whatsoever)

No surprise to me there.

A well know problem with the X-series is the capstan belt that degrades and goes stickey. Then, when you turn the machine on, it jams the capstan motor & flywheels, damaging the motor.
But that should not show up as "nothing working", so it is not likely the main problem. BUT for that reason, don't try to run the machine in a faulty condition - it will just make the repair more costly.

A totally dead machine is often the easiest to repair - typically only one component in the power supply has failed.

The X-series also will do nothing if no tape is threaded. Be sure to thread the tape correctly - NOT like in the photo Hans posts online with his self-promotion adverts showing a Teac X incorrectly threaded!

Offline neilpainter

Re: Revox A77 help,please
« Reply #13 on: May 10, 2019, 10:51:43 AM »
Thanks very much for the replies guys, as I repeat the knowledge and assistance out there is astounding!

Offline neilpainter

Re: Revox A77 help,please
« Reply #14 on: May 16, 2019, 10:53:27 PM »
Steerpike and Mike thanks again for the input, you've got me all enthusiastic about resurrecting this Teac X-1000 Mike I spoke to Bobby and he says he will definitely have a look at it so here's hoping! I want to get this magnificent machine up and running and lend it (permanently?) to my friend Jonathan Handley the main man of the Radio Rats who is living in Hilton/PMB so he can use it in his home studio ... he is still writing and recording! Jonathan has 2 Foster studio recorders a G248 and E-2 (and an Ampex!) which need some attention I will also speak to Bobby about these. Mike, I have already sent my Nad CR7 to Bobby, he sounds most enthusiastic so thanks again, I am indebted.