One of my M-125 has a humming sound that is very noticeable in the speaker. I replaced the input jack as the rca cable was loose fitting and swapped out both driver tubes. Also plugged it in to a different outlet. Any other suggestions? the amp has low hours on it. Also noticed that when i put only 2 power tubes in the right 2 slots (when looking from front) i have no hum. Moving to left gives hum and bias goes very high. Bias goes up to 1400 mv. Bias also goes whacky and fluctuates wildly with tubes in left 2 sockets. If i try to adjust it lower, a thumping sound is heard in the speaker. I resoldered all connections and measured all resistors. Also tightened all socket pins. Thanks
3 posters
VTA M-125 hum
ericoto- Posts : 26
Join date : 2013-12-11
Did you notice before you switched input and changed driver tubes? What tubes are you using a drivers? If it worked then go back an reexamine your work, could be a poor connection or a short.
Tom- Posts : 217
Join date : 2011-04-04
I thought power tubes went front and/or back on the m-125? Not left and right? Two in either front or back for 60w, four for 120w with correct bias?
|
|
|