2. amps-preamps
  3. 1250637079

Vibrating Woofer, old tubes?

I have a dual mono tubed phono section that even has an active tube line input for a cd player. Now, I have a little problem with it, and I am not sure what the cause is.

When I open the volume wide open it causes my speakers to vibrate and gives and it hums in strange way. The weird thing: It goes away after I let the unit heat up for a couple of hours, usually. After using it for a couple of hours I can open the volume pot wide open, I mean wide open and it is as quite as a Church.

Is the thing scrap metal or is it something easy to fix?

Can it just be the tubes needing to be replaced?

I am a little freaked out about, becuase I really do love the item and have no desire to purchase another tube phono section or even tube pre at all; though I would like to be able to use it without damaging my loudspeakers. I will be getting a new pair any day now and I am a little worried. Please help me out guys, thanks a million.
dfelkai

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,632 posts
 
You have bad filter capacitors in the power supply. This condition is called 'motorboating' and can be affected by temperature and the length of time that the unit is one.

It is something that needs service! I would not operate this unit until this is fixed. If left unattended, you run a good risk of frying the power transformer! Trust me, that is a very unpleasant experience.
atmasphere's avatar
atmasphere
11,632 posts
 
Dfelkai, most shops in the US will charge about $75-$80.00 per hour. That allows them to pay the technician and their overhead. Filter caps do not take a long time to change, and this is entirely off the top of my head, so unless there is something really unusual about this preamp I would guess that 2 hours is all that is needed.

Without even seeing the unit, that's the best I can come up with- diagnosing at a distance has its problems :)
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