Hallicrafters S120 hum at no vol and hum with volume

[maxhifi]

1. Try substituting the tubes with new ones, to rule out heater to cathode leakage.

2. Verify that the new capacitors are grounded to the same point as the original can, this can be critical.

3. Verify the "across the line capacitor" is good and connected properly

4. Check if the volume control is bad, jumper the middle and negative terminals of the volume control to see if hum goes away.

[tubetwister]

Originally Posted by maxhifi

1. Try substituting the tubes with new ones, to rule out heater to cathode leakage.

2. Verify that the new capacitors are grounded to the same point as the original can, this can be critical.

3. Verify the "across the line capacitor" is good and connected properly

4. Check if the volume control is bad, jumper the middle and negative terminals of the volume control to see if hum goes away.

Thanks and all good points

1. All new NOS tubes will be ordered before I log off windows 10 and rolled in one at a time to eliminate an offending tube if any out of the lot of (4) and all rolled in anyway like I intended before I bought the radio .



2. Cap grounds are grounded to same as OE and double checked ,


3. AC line cap seems to be OK but I don't have a CAP tester and maybe should replace it anyway and probably will . I thought about that and may have it on my Cap order and if not I will get one .

4. Volume plays and works fine outside of a too loud to allow at low volume AC hum but there's a specific and notorious suspect .001 film cap there I will replace and Yes I can jumper the pot anyway . maybe the pot is leaking an ac potential or DC ripple in to the audio path , good point but the hum amplitude is constant and actually garbles speech at lowest volumes .