Meanwhile I found this page (English). Mentions hum in one channel coming from 6AN8 driver valve.
http://www.thermionic.org/sansui1k.html
http://www.thermionic.org/sansui1k.html
Whatever the position of VR5? Hum should decrease with VR5 fully CCW... It suggests hum is injected in V6a's grid. Weird...samgraysound said:When top of VR5 is connected to ground via 50R, hum remains.
That can be easily checked out; it doesn't explain hum, though.Script said:Read that they age by slowly increasing resistance.
Changes in resistance value are rarely significant. However, carbon comp resistors can be noisy. But they're not everywhere; notice how some resistors (particularly in the phono preamp) are marked with a sign that means "noiseless".Better replace them with metal film (?)
squarewave said:Well that is pretty strange. That pot is pretty busy in that it's dual, has a tap for what appears to be some kind of filter and switches connected to the input. But if you just terminate the "top" of VR5 (no 50R, just ground it) and try different positions and switches what happens? If it's fully CW or fully CCW there should be no hum. Right? If it's in the center position, then the source impedance is going to be 100k or so in which case that first stage could be picking up heater hum (maybe because of the heater-cathode isolation issue PRR mentioned).
Check basic continuity of the pot with a meter. Maybe you have a bad solder joint. Try each position of the pot and sanity check the values. Maybe the wiper is loosing contact.
I was sort of leaning toward some kind of grounding problem created by a ground loop with another piece of gear. But this is not connected to any other gear at all right? You just have it connected to stand alone speakers? If you have any connection to another piece of gear then it's still possible that there could be a ground loop issue. Does the power chord have an earth pin? Is the chassis connected to it at the mains input?
Script said:Meanwhile I found this page (English). Mentions hum in one channel coming from 6AN8 driver valve.
http://www.thermionic.org/sansui1k.html
abbey road d enfer said:Whatever the position of VR5? Hum should decrease with VR5 fully CCW... It suggests hum is injected in V6a's grid. Weird...
Does hum change when reversing the mains plug?
Does hum change when pressing the Tape Monitor switch?samgraysound said:Hum does not change when reversing mains plug. Hum does decrease with CR5 fully CCW.
Enter your email address to join: