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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, 2:24 pm | #21 | |
Octode
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,654
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Re: Revox A77 aficionados in Scotland ?
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21st Jun 2021, 2:26 pm | #22 | |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,288
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Re: Revox A77 aficionados in Scotland ?
Quote:
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
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21st Jun 2021, 2:33 pm | #23 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Revox A77 aficionados in Scotland ?
There are various copies of the schematic and service manuals here in varying quality, FOC or registration, I'm looking at service manual 4 (not the MK4) if that's any use:
https://www.vintageshifi.com/reperto...oogle_vignette Lawrence. |
21st Jun 2021, 3:40 pm | #24 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,603
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Re: Revox A77 aficionados in Scotland ?
The fuses are AC voltages from the secondary windings of the mains transformer.
For fuse F103 the winding voltage is shown as 22VAC, for fuse F102 the winding voltage is shown as 24VAC. To measure these AC voltages at either side of the fuses you would have to connect the other side of the meter (set to AC voltage) to the respective other end of the winding that connects to the respective bridge rectifier (shown as connection D5 for the 22VAC and connection D7 for the 24VAC). Do not know what sort of reading you might get if you tried to measure DC voltage either side of the fuses but it would be misleading. I would say probably easier just to measure the +21V & +27V DC voltages at the smoothing capacitors C101 & C104 ( +ve connection) respectively, assuming they are practically accessible, with the meter negative lead connected to 0V/ground David Last edited by DMcMahon; 21st Jun 2021 at 3:46 pm. |
21st Jun 2021, 4:08 pm | #25 |
Moderator
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Location: Ipswich, Suffolk, IP4, UK.
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Re: Revox A77 aficionados in Scotland ?
C101 is on the wrong side of the voltage regulation circuit for measuring the DC voltage across it. Better to measure it across suitable interconnect points. AD1 and AD2?
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
21st Jun 2021, 6:51 pm | #26 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,603
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Re: Revox A77 aficionados in Scotland ?
On 2 schematics I have checked the +ve side of C101 connects directly to AD1, AD2 is the 0V so appears identical to me to what I suggested ?
David |
22nd Jun 2021, 10:34 am | #27 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Revox A77 aficionados in Scotland ?
Yes, measuring from ground to the +ve of the reservoir capacitors will give the B+ supply voltages.
Lawrence. |
19th Oct 2021, 4:56 pm | #28 |
Triode
Join Date: Mar 2014
Location: Dunfermline, Scotland, UK.
Posts: 23
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Re: Revox A77 aficionados in Scotland ?
Sorry this response is a little late and you may have sorted your A77 by now but I own and have fully restored four of these machines. I live in Dunfermline and would be pleased to offer you any practical assistance if you'd like to get in touch.
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