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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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21st Jun 2021, 5:35 pm | #1 |
Diode
Join Date: Jun 2021
Location: Glasgow, Lanarkshire, Scotland, UK.
Posts: 2
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Revox A77 Fast Forward failure
Hello.
I'm working on an A77 Mk III which has been in a cupboard for the last 23 years. Play, Record and Rewind now work as they should but Fast Forward does not work at all. I replaced all the capacitors on the motor drive board and cleaned the relay contacts. Relay C for Fast Forward actuates and holds when the push button is operated. AC voltages for the right hand reel motor are shown in the service manual as Play - 55; Fast Forward - 105; Rewind - 15. The corresponding voltages I'm measuring are 73, 24 and 6. The AC feeds to the board measure OK. I'd be really grateful for any suggestions as to what could be causing the problem. |
21st Jun 2021, 6:14 pm | #2 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Revox A77 Fast Forward failure
Were those voltages measured at the transformer with respect to the 0v connection?
Lawrence. |
22nd Jun 2021, 2:00 am | #3 |
Octode
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,965
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Re: Revox A77 Fast Forward failure
With brakes off and the reel motor button in are both reel platters equally easy to turn by hand?
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22nd Jun 2021, 9:15 am | #4 |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
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Re: Revox A77 Fast Forward failure
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22nd Jun 2021, 8:09 pm | #5 |
Diode
Join Date: Jun 2021
Location: Glasgow, Lanarkshire, Scotland, UK.
Posts: 2
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Re: Revox A77 Fast Forward failure
Thanks for the responses. Platters turn freely, no binding. I checked that I was using the correct terminals to measure voltages and found a fault. I had replaced a couple of components on the capstan speed control board and when I reinstalled it I managed to reverse the connections from the 130 volt winding on the transformer. Sorted that and Fast Forward is restored. Spot the muppet. Thanks again for the input.
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22nd Jun 2021, 9:22 pm | #6 |
Octode
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,965
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Re: Revox A77 Fast Forward failure
Glad you found the fault. I had read you saying the fault had developed while sitting idle for 23 years, rather than the work you subsequently did on it.
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22nd Jun 2021, 11:22 pm | #7 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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Re: Revox A77 Fast Forward failure
If making the error made you a muppet, then finding and correcting it moved you further in the unmuppet direction than the error moved you muppetwards in the first place. The reason for the difference is that you now have the benefit of experience you would not have gained otherwise!
Everyone makes mistakes. What separates the good guys and the bad guys is what they do afterwards. David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
22nd Jun 2021, 11:42 pm | #8 |
Octode
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,965
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Re: Revox A77 Fast Forward failure
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23rd Jun 2021, 10:02 am | #9 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Revox A77 Fast Forward failure
I thought it might be that, the voltages measured were more or less the same as some of the voltage differences between the transformer taps.
Lawrence. |