|
Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc. |
|
Thread Tools |
20th May 2022, 6:37 pm | #1 |
Triode
Join Date: May 2019
Location: Flitwick, Bedfordshire, UK.
Posts: 21
|
Revox A77 MK4 Dolby Calibration
Currently working on this deck. I've re-capped all boards including the two Dolby processors.
I started on the Dolby calibration and successfully did the first part - The record processor. However, I've run into a problem with the Dolby play back calibration. I've set up my signal generator at 5kHz output about 3mv and attached this to P5 and ground Attached my millivoltmeter to P7 and ground - no output! I checked the voltages on the playback card transistors (from the schematic) and all appear to be OK. Any suggestions as to where I should be looking next? |
30th May 2022, 9:49 am | #2 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
|
Re: Revox A77 MK4 Dolby Calibration
Have not had a chance to look at the schematic but I would suggest using a scope |(if you have one) to check the injected signal through the transistors to see where it is being lost and then work out why.
David |