New Sebatron vmp4000e owner -- Noisy transformer??
I just purchased a vmp4000e. And when you turn it on, you immediately notice a buzz/hum coming from the unit! Upon removing the case, it's obviously coming from the transformer. To those of you who own Sebatron preamps, are your units silent when switched on? This problem has nothing to do with the audio path. I'm talking strictly about the hardware itself being noisy. Please let me know if you have noticed any noise coming from the transformer section of the preamp.
I have a 4000e...and I've been under the hood a few times...and fixed a few minor issues.
Unplug the unit....
First thing...trannys do have a bit of "vibration"...though when properly mounted/isolated...you should not hear it.
What I noticed on my unit was that the metal plate which divides the power side from the rest of the audio circuits...is only mounted at one point...and it can easily pivot and lean on the tranny side.
It may be what is actually making the buzzing noticeable...try screwing down that one screw a bit tighter if the plate indeed has moved up against the trannys.
I think I mentioned this to Sebatron awhile back...that they should add a second hold-down screw to that metal plate ( and another support screw in the middle of the audio PCB, 'cuz changing tubes 2 & 3 can cause the PCB to flex too much...and it might crack).
Second...check the mounting/isolation screws for the actual trannys...see if they are loose...or if something doesn't look right.
Third...check all the wiring from the trannys and look if any of it got pinched in the mounting/isolation screws/posts (you have to look under the PSB also).
I found one pinched wire on mine, and the wire had been exposed due to the pinch...so it was going to chassis ground. Easy fix.
If all of that is fine...then it just might be a bad tranny... :(
My 4000e is nice a quiet...no buzz/hum... 8)
Keep us posted.
First of all, thank you for the reply. I appreciate it.
If yours is silent, there must be something wrong with mine. I'm going to take another look tonight, but if I can't solve the problem, I'm just going to exchange it for another one while I still can.
I'll let you know what happens.
mine is totally silent.
All four of mine work like a dream... 8-)
I exchanged the vmp4000 for a new one, which is silent. There must have been something wrong with the first one. Greg at proaudiotoys was very nice about the whole situation. Now I can get back to writing music! 8-)