I have a newly acquired Pas3x that I've been doing a bit of work on. One item was a bit of low level hum from the right channel that did not change volume with the volume control. It was reduced somewhat by going through the Pas per the instructions and eliminating some twisted pairs that should not have been twisted. I also re-flowed a lot of solder joints just to be sure but a bit of low level hum remained. The hum was barely noticeable and totally covered by any signal source playing. Still, I didn't like the faint hum with no signal.
I totally eliminated the hum with a jumper between pin 1 and pin 8 of PC5. I have no idea why that would eliminate the hum but it did. The preamp is dead-quiet now. I'm sure there is some problem in the original wiring by the kit builder that makes this jumper do what it does but I can't find anything that seems wrong other than that twisted pair issue.
The Pas is oem except for Roy's 1st level power supply and new caps/tubes and I want it to function as original with all filters/switches/tone controls. I have ordered a new jack board and volume control for it but for now that will be the extent of the changes.
I totally eliminated the hum with a jumper between pin 1 and pin 8 of PC5. I have no idea why that would eliminate the hum but it did. The preamp is dead-quiet now. I'm sure there is some problem in the original wiring by the kit builder that makes this jumper do what it does but I can't find anything that seems wrong other than that twisted pair issue.
The Pas is oem except for Roy's 1st level power supply and new caps/tubes and I want it to function as original with all filters/switches/tone controls. I have ordered a new jack board and volume control for it but for now that will be the extent of the changes.