337alant
Negatively Biased
I recently bought a very nice example of the Revox B77 its in excellent condition and the heads are excellent with very little wear, the downside of this one is its only the 3-3/4 & 7-1/2 IPS version but these decks still sound excellent at 7.5”ips
The B77 is a consumer deck classic and has RCA phono In and Outputs, the PR99 mk 1 is virtually identical but was meant for professional use with XLR in/outs
These machines are very robust being built on a aluminium chassis and all circuit boards are removable for service so they are relatively easy to work on
IMG_2208 by Alan Towell, on Flickr
B77 by Alan Towell, on Flickr
Before switch on I took the back off and had a look round for and leaking capacitors or split Evox Rifa X2 caps that may burn out on switch on, anyway all was well and the X2 cap on the mains input had been renewed.
So I switched it on and everything worked as it should. I did notice some channel imbalance and the pots and switches were scratch so want cleaning
To get at these pots and switches you have to strip down all of the bottom panel as they are all screwed into the audio interconnection board so you also have to remove all of the audio cards and all interconnecting wires. Tip it to take lots of photo’s so you know how everything goes back together
To cure the scratchiness you clean the gold plated pads on the circuit board and the switch connections, work the switched back and forth multiple times after spraying with Deoxit .
There is another item to clean on this board its the speed slider switch which has multiple connections that get tarnished so need cleaning and lubricating, I used deoxit then fader lube
IMG_2282 by Alan Towell, on Flickr
IMG_2285 by Alan Towell, on Flickr
IMG_2289 by Alan Towell, on Flickr
IMG_2397 by Alan Towell, on Flickr
IMG_2323 by Alan Towell, on Flickr
The B77 is a consumer deck classic and has RCA phono In and Outputs, the PR99 mk 1 is virtually identical but was meant for professional use with XLR in/outs
These machines are very robust being built on a aluminium chassis and all circuit boards are removable for service so they are relatively easy to work on
IMG_2208 by Alan Towell, on Flickr
B77 by Alan Towell, on Flickr
Before switch on I took the back off and had a look round for and leaking capacitors or split Evox Rifa X2 caps that may burn out on switch on, anyway all was well and the X2 cap on the mains input had been renewed.
So I switched it on and everything worked as it should. I did notice some channel imbalance and the pots and switches were scratch so want cleaning
To get at these pots and switches you have to strip down all of the bottom panel as they are all screwed into the audio interconnection board so you also have to remove all of the audio cards and all interconnecting wires. Tip it to take lots of photo’s so you know how everything goes back together
To cure the scratchiness you clean the gold plated pads on the circuit board and the switch connections, work the switched back and forth multiple times after spraying with Deoxit .
There is another item to clean on this board its the speed slider switch which has multiple connections that get tarnished so need cleaning and lubricating, I used deoxit then fader lube
IMG_2282 by Alan Towell, on Flickr
IMG_2285 by Alan Towell, on Flickr
IMG_2289 by Alan Towell, on Flickr
IMG_2397 by Alan Towell, on Flickr
IMG_2323 by Alan Towell, on Flickr