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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 30th Apr 2019, 7:33 pm   #21
Ted Kendall
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Default Re: Revox A700 - A15 Board layout (old Style)

It seems there are many A700s being broken up at the moment, maybe because the VU meters go for silly money, so you may get lucky. However, the earlier board works perfectly well, when it works, and decent IC sockets would benefit reliability, given the numer of extra chips involved. The method I used was to take a pair of cutters to the soft plastic surround and remove the pin sockets individually. This can be done by chopping them off flush with the board and removing the stubs with a solder sucker. Care is the watchword, but it's certainly do-able.
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Old 30th Apr 2019, 10:08 pm   #22
stewartrose
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Cool Re: Revox A700 - A15 Board layout (old Style)

Hi Ted,

Yes ! paid £139 for my Vu Meters, I shall start stripping the board down, I know there is nothing wrong with the board, because it worked fine...
Just bad connections which I proved on 2 ic's so far...
But I will go after an other board even if it is a spare...

Thanks for your Advice...

All the best from Alan
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Old 30th Apr 2019, 10:24 pm   #23
julie_m
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Default Re: Revox A700 - A15 Board layout (old Style)

Those IC sockets look well past their best! Some high-quality turned-pin replacements will make a world of improvement.

Look upon it not as hours of tedious work alternately priming and firing a desoldering pump, but as an opportunity to treat yourself to that vacuum desoldering station you have always wanted ..... Available from the same sorts of places you'd have to go anyway for a reel of solder braid and a flux pen that you probably would need to help things along if you were determined to do the job by hand, so it can't hurt just to have a quick peek before you hit the checkout
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Old 1st May 2019, 12:09 pm   #24
stewartrose
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Wink Re: Revox A700 - A15 Board layout (old Style)

Good Morning Julie,

It will be a long time before I hit checkout, these boards are hard to get hold of, so I have already mad a start to strip the board down of ic's


All the best from Alan
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Old 1st May 2019, 8:23 pm   #25
Chris55000
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Default Re: Revox A700 - A15 Board layout (old Style)

Evening Alan!

If you're thinking of depopulating your 1.067.234 capstan speed PCB before rebuild/repair, could I have two more photos of each side of the pcb laid on a flat surface please?

The reason I ask is because the top part of the pcb where the speed control switches is covered by metal shielding both sides, so I'd have to try and tack on a bit of the 1.067.235 diagram on your pictures as they come, and tracing that bit is difficult – tracing an unpopulated pcb that's laid flat is really so much easier!

Chris Williams
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Old 2nd May 2019, 7:15 am   #26
stewartrose
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Talking Re: Revox A700 - A15 Board layout (old Style)

Good Morning Chris,

I have tried to remove ic's with a proper DE soldering machine, but tracking is lifting, so I am going to give up that idea and wait for a 235 board to become available...


All the best and Thanks from Alan
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Old 2nd May 2019, 3:07 pm   #27
julie_m
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Default Re: Revox A700 - A15 Board layout (old Style)

Quote:
Originally Posted by stewartrose View Post
I have tried to remove ic's with a proper DE soldering machine, but tracking is lifting
It sounds a bit counter-intuitive, but what you need is more power!

It takes a certain fixed number of Joules of heat to turn a kilogram of solder from solid to liquid. (A typical solder joint will only be a fraction of a gram, but the published data always refer to whole kg.) Your (de)soldering iron is only putting a certain fixed number of Joules into the joint every second (aka its Wattage). And the solder won't even begin to melt until it reaches a certain temperature anyway. The problem is that the heat will also leak away at a certain rate to where it's not wanted; overheating sensitive electronic components, softening PCB track adhesive and plastic insulation and possibly even burning fingers.

Now, if you have a 15W iron and the leakage rate is 5W, that means there are only 10W available for warming up and melting the solder. If you used a 45W iron on the same joint, there would be 40J of heat going into the solder every second; so the job of melting would be accomplished in a quarter of the time. Therefore, the total amount of energy lost (and therefore, available for doing damage .....) would also be reduced by a factor of four.

You can prove this for yourself easily enough with two differently-rated soldering irons. Holding a component in position by hand is a lot less pleasant if you have only a low-power soldering iron.
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Old 2nd May 2019, 6:10 pm   #28
Chris55000
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Default Re: Revox A700 - A15 Board layout (old Style)

Hi!

I recommend anyone wishing to service any valuable piece of vintage equipment (and certainly something like a Revox with over twenty individual PCBs!) – invests in one of these:–

https://www.amazon.co.uk/ZD-915-Deso...ix=zd91&sr=8-1

I have one at home myself and have no problem getting components out of double–sided and plated–thro' modern equipment PCBs with this, including all standard DIP devices, I feel the investment in one of these by the OP will prevent a great deal of damage to the boards in the Revox!

Chris Williams
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Old 2nd May 2019, 7:01 pm   #29
Radio Wrangler
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Default Re: Revox A700 - A15 Board layout (old Style)

I've always found the PCBs in Studer/Revox stuff to be particularly fragile in terms of track/psd damage. The substrate may be glassfibre but the copper might as well be stuck on with hide glue.

David
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Old 2nd May 2019, 7:09 pm   #30
stewartrose
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Red face Re: Revox A700 - A15 Board layout (old Style)

Hi David,

You can say that again, and what is worse they use in line sockets for ic's, if they had used a normal ic socket, the plastic could have been lifted away, and the pins would fall out when heated...
Cant do that with inline sockets..

All the best from Alan
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Old 16th May 2019, 6:59 pm   #31
Ted Kendall
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Default Re: Revox A700 - A15 Board layout (old Style)

Quote:
Originally Posted by Chris55000 View Post
Hi!

I recommend anyone wishing to service any valuable piece of vintage equipment (and certainly something like a Revox with over twenty individual PCBs!) – invests in one of these:–

https://www.amazon.co.uk/ZD-915-Deso...ix=zd91&sr=8-1

I have one at home myself and have no problem getting components out of double–sided and plated–thro' modern equipment PCBs with this, including all standard DIP devices, I feel the investment in one of these by the OP will prevent a great deal of damage to the boards in the Revox!

Chris Williams
YMMV, but I bought one on this recommendation and it's . It worked initially and then the bit oxidised to the point where it wouldn't melt
solder. Should have known - it's out of the same factory as the soldering station which failed on me. It's going back whence it came. Something along these lines which actually works would be a great asset, but don't waste your time with this.
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