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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 25th Apr 2019, 1:11 pm   #1
stewartrose
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Cool Revox A700 - A15 Board layout (old Style)

Good afternoon everyone,

I Need so help please, my A700 appears to have the old style A15 Capstan board in it, 1.067.234, it has 11 ic's on it, but I dont have a board layout with component notations on it...

Can anyone help please...

All the best from Alan [ Blackpool ]
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Old 26th Apr 2019, 9:06 am   #2
Chris55000
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Default Re: Revox A700 - A15 Board layout (old Style)

Hi!

Can you PM me high resolution pictures of the top (component) sides and bottom (copper) sides of your board please?

I can make you an annotated layout drawing from this – is the pcb single–sided or double–sided copper?

Chris Williams
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Old 27th Apr 2019, 7:15 pm   #3
stewartrose
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Wink Re: Revox A700 - A15 Board layout (old Style)

Hi Chris,

I am in the middle of getting the board out, not to easy...

All the best and thank you from Alan
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Old 28th Apr 2019, 4:21 pm   #4
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Default Re: Revox A700 - A15 Board layout (old Style)

Hi!

I have Abacom's excellent Circuit Diagram SPlan 7 & Sprint Layout 6 together with Mr. Tiong's books on PCB Reverse Engineering with examples he provided for me, all I need to make some quality documentation of your 1.067.234 Capstan Speed Controller PCB for you, with the aid of the photos I requested!

Incidentally, the three digits "067" in the PCB number are the Studer design series no - this indicates the PCB was originally designed for the A67 series!

Chris Williams
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Old 29th Apr 2019, 7:46 am   #5
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Default Re: Revox A700 - A15 Board layout (old Style)

Good Morning Chris,

I have uploaded them as an attachment, if you want a bigger version
I can load them on my website and give you the urls…

Pleas let me know..

All the best and thank you....
Attached Thumbnails
Click image for larger version

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ID:	182079   Click image for larger version

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Old 29th Apr 2019, 7:48 am   #6
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Default Re: Revox A700 - A15 Board layout (old Style)

http://www.g0wda.com/DSC00090.JPG
http://www.g0wda.com/DSC00091.JPG
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Old 29th Apr 2019, 6:22 pm   #7
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Default Re: Revox A700 - A15 Board layout (old Style)

Evening Alan!

I've downloaded your pictures safely and get started on some new documents for you later tonight !

I'll let you know if I need any additional pictures or info (e.g., from the machine's nameplate!).

Kind regards,

Chris Williams

PS!

Unfortunately I haven't been able to locate a s/h board of the same type I can use myself!
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Old 29th Apr 2019, 7:46 pm   #8
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Cool Re: Revox A700 - A15 Board layout (old Style)

Ok Chris, Thank you...

All the best from Alan
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Old 30th Apr 2019, 12:12 am   #9
Michael Maurice
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Default Re: Revox A700 - A15 Board layout (old Style)

Gosh, well I have serviced a few A700's but never seen one of those! Its not even in the service manual!

What's wrong with it?
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Old 30th Apr 2019, 6:39 am   #10
stewartrose
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Wink Re: Revox A700 - A15 Board layout (old Style)

Good Morning Michael,

Well following the oscillator circuit I have found ether broken/corrosive ic socket terminals, so If I can get an other board eg 067.235 then I will remove all IC Sockets and clean the board, and put new ic sockets back in..


Fault shows its self is capstan runs all the time at one speak, pressing any speed changes the light but not the speed of the capstan, and TP1 is 1.2v, and R32 has no effect on TP1...

I have the circuit diagram, but no component layout.


All the best from Alan
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Old 30th Apr 2019, 6:52 am   #11
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Default Re: Revox A700 - A15 Board layout (old Style)

For those who want a copy of the circuit heres a copy
https://www.g0wda.com/RevoxA700ServiceManual.pdf

From Alan
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Old 30th Apr 2019, 7:40 am   #12
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Default Re: Revox A700 - A15 Board layout (old Style)

Quote:
Originally Posted by Michael Maurice View Post
Gosh, well I have serviced a few A700's but never seen one of those! Its not even in the service manual!
I have one - this was a stop-gap design used in the earliest machines pending the arrival of the TDA 1000 IC. There was something similar in the Science Museum once - a Thorn colour TV showing a substitute card used when development of an IC was held up.
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Old 30th Apr 2019, 8:19 am   #13
stewartrose
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Default Re: Revox A700 - A15 Board layout (old Style)

Good Morning Ted,

the 60,000 question is can I put a 067.235 in place of a 067.234 please

All the best from Alan
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Old 30th Apr 2019, 8:28 am   #14
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Default Re: Revox A700 - A15 Board layout (old Style)

Morning Alan!

I think you can, as reference to the A700 S.M. shows 1.067.235 in the overall machine's layout diagram with 1.067.234 in brackets alongside it!

However I will still be carrying out my documentation project for completeness and for those who have a "234 board and don't wish to attempt modifications!

Please don't forget tho', when you fit a '235 board you're adding the TDA1000 to the design, so I would advise obtaining another spare TDA1000 if you can, as this device is prone to internal failure!

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Last edited by Chris55000; 30th Apr 2019 at 8:35 am.
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Old 30th Apr 2019, 8:37 am   #15
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Default Re: Revox A700 - A15 Board layout (old Style)

Quote:
Originally Posted by stewartrose View Post
the 60,000 question is can I put a 067.235 in place of a 067.234 please
I can see no reason why you cant.

I'd be very wary of replacing those sockets as the board is double sided and could easily be damaged.
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Old 30th Apr 2019, 8:40 am   #16
stewartrose
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Default Re: Revox A700 - A15 Board layout (old Style)

Hi Michael,

That was my thoughts, all I have to do is find one....

All the best from Alan
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Old 30th Apr 2019, 11:56 am   #17
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Default Re: Revox A700 - A15 Board layout (old Style)

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Originally Posted by stewartrose View Post
Good Morning Michael,

Well following the oscillator circuit I have found ether broken/corrosive ic socket terminals, so If I can get an other board eg 067.235 then I will remove all IC Sockets and clean the board, and put new ic sockets back in..
Just a word re long term preventative maintenance.

I'm guessing the probable cause of the corrosion, or a strong contributor, is dust falling on the top surface of the PCB over a long period, which is made worse by any exposed metal parts or pcb tracks. This applies to the A700 main control pcb as well. I'd always give a good clean to the top sides of both PCB's and then repair any corrosion to tracks etc. Especially for anyone who owns a large collection of machines, covering up the upward facing ventilation holes of the machine when not in use seems a no brainer.
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Old 30th Apr 2019, 12:28 pm   #18
stewartrose
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Wink Re: Revox A700 - A15 Board layout (old Style)

Hi Tim,

I agree with you 100% I brought the machine 6 months ago, and slowly going through it replacing or repairing different parts, the board in question has been washed in alcohol, but I think the problem is corrosion between the IC pins and the socket strips...

All the best from Alan
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Old 30th Apr 2019, 1:02 pm   #19
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Default Re: Revox A700 - A15 Board layout (old Style)

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Originally Posted by stewartrose View Post
Good Morning Ted,

the 60,000 question is can I put a 067.235 in place of a 067.234 please

All the best from Alan
Straight replacement, if memory serves.

As to those IC sockets, I replaced them on mine before I realised it couldn't be done...but seriously, it does need care, though the resultant gain in reliabilty is worth the trouble.
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Old 30th Apr 2019, 2:07 pm   #20
stewartrose
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Wink Re: Revox A700 - A15 Board layout (old Style)

Hi Ted,

All Ii have to do is find one that someone wants to sell at a reasonable price..

All the best from Alan
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