Hey everyone! Okay, I have a hum problem on my PAS 3 in the phono section only. It’s quiet with the volume knob at zero but it gradually increases with the volume and also increases when the bass is increased. The hum sounds like 100hz (I’m in Sweden so a 50hz country). The hum is more prominent in the right channel and barely noticeable in the left channel at full volume. If I use shorting plugs into the the inputs the hum moves from the right side to the left side. I’ve replaced the volume control, the can capacitor and all other electrolytics. All carbon resistors has been replaced with metal film and the selenium rectifier has been removed and silicon diodes have been put in. The heater voltage is exactly 24v. I’ve removed the old RCA connectors as they couldn’t hold any cable in place and installed a replace my. Dynakit. This has all been done at various points during soon to be 3 years. I can’t remember if it was humming in the phono section before I started working on it. Not optimal not knowing if any of my work caused the hum. But the PAS and the ST 70 that came with it was humming quite badly on all inputs and independent from each other because of faulty can capacitors. Replacing them got rid of the hum, but I didn’t check the phono section properly. Anyone has an idea on where to start? I’ve rolled the tubes between the two boards (2 new JJs and 2 old tested Sylvanias) and cleaned the sockets several times. All grounding points looks okay and according to the manual. I’ve reflowed all of them though, just to be sure.
Cable routing is important. Try to route ground and B+ exactly as the manual.
Line board hum is often reduced by adding a jumper between 1 and 8 on the line board.
( i know you have much hum on the ohono board)
You may have hum via the filament, do you have any means of using a DC source ( 24V ) for testing ?
Line board hum is often reduced by adding a jumper between 1 and 8 on the line board.
( i know you have much hum on the ohono board)
You may have hum via the filament, do you have any means of using a DC source ( 24V ) for testing ?