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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 3rd Dec 2017, 12:41 pm   #1
Linnovice
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Default Revox B77 query

Hi all, Iím in the process of renovating a B77 HS Iíve inherited. I have come across a very weird problem though.
On the Tape Drive Control PCB I am missing a chip. IC2 on the schematic has been replaced with a mares nest of wires (they look like fine telephone wires). They have been cut so have no idea how they connect. So, Iíd like to revert the board back to standard. The manual quotes a part number as:
IC2 = 1.177.317.51 PROM 32 X8
I presume this is a Progrmable Read Only Module? If so, where can I get a replacement from? Iíve not come across this before so am stumped. Anyone have a suggestion?
Mike
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Old 3rd Dec 2017, 9:04 pm   #2
Marotick
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Default Re: Revox B77 query

Hi, if you want is I have one of the IC PROM 32x8 of type N82S123N.
I ask for that chip 50 euro without shipping.
Shipping is about 5 euro.

Jack Marotick
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Old 3rd Dec 2017, 11:28 pm   #3
Michael Maurice
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Default Re: Revox B77 query

That board and later ones are as far as I know interchangeable, so my advice to you is get yourself another board.
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Old 4th Dec 2017, 6:22 am   #4
Linnovice
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Default Re: Revox B77 query

Hi Jack, thank you for your offer but I think it more cost effective to look out for a replacement board complete, as has been suggested. Mike
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Old 4th Dec 2017, 7:49 am   #5
Ted Kendall
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Default Re: Revox B77 query

MkI and Mk II use different transport boards - the later type has a more benign take-up on starting.
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Old 5th Dec 2017, 11:05 am   #6
Linnovice
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Default Re: Revox B77 query

Hi all, Iím now very confused.
Iíve tried a board out of a PR99 and all works ok. Iíve got a spare TCB (Iíd forgotten I had it previously) and put that in and I still have a problem. If I turn the machine on with no tape all is well. If I turn it on with tape loaded it immediately goes into play and runs. If I stop it all is well again and it works normally.
Iíve checked the caps C16 and C17, both are in spec. Iíve changed the IC4 and it made no difference. Now Iím stuffed. Can anyone suggest what the problem is?
The fault is there only when turning on with tape loaded and after then pressing stop all reverts to normal. Everything else is good and within spec.
Help!
Mike
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Old 19th Feb 2018, 9:57 pm   #7
QUADGOD
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Default Re: Revox B77 query

Sounds like the timer mode is on so tape will run as soon as powered up
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