svt 2 problem

Try plugging a cord from the send to the return jack.

 

I had a similar problem with the same amp long ago. The input jacks needed resoldering. Had that done and never had another problem with it (other than the weight).

 

Sorry, I meant the preamp out to the power amp in. And I have one of these amps so I know it has it.

 

Could be one of the pre tubes going? seeing only one has been replaced?

As brothernewt said, its probably an input problem

And as timV said, try an instrumental lead from pre amp out to power amp in, ive heard one instance of a problem internally between those connections that wasnt present when you connected them externally

The hum that you mention, does it get louder when you turn the volume up?

(btw, damned good amp!)

 

if you bypass the internal part that joins the pre and power and it works fine then you know that thats whats wrong

if its increasing with volume its usually not a good thing, take it to a tech, get it the once over, more than likely just a tube going funky

 

Sure sounds like an opne circuit that is intermittent with heat..... As to where exactly it is, we are all guessing.

The pre out to power amp input jumper makes sense, if the "normaled through" connection inside the jack isn't so good anymore due to corrosion and bar crud. In fact. just plugging a plug into the power amp input usually fixes that temporarily. Contact cleaner is good to use, the Caig Laboratories stuff has a good reputation.

Yes it could be a bad solder connection.

Yes it could be something tube-wise. I'd think about cleaning contacts on all the tube sockets also... that can fix odd problems.

As for us all guessing on the location, you can make some rough but definite determinations....

If you have another amp, and plug the pre-out from SVT into that amp, you can see if it still happens with just the preamp alone (do plug in a speaker to the SVT as a load, please).

Doing the reverse will find it if it is in the power amp and not the preamp.

See which connection still does the drop-out. It is in the part of the unit you are using in that connection.

If it is in neither one, it may have been the jacks, and they have been cleaned by getting used.

 

i'd say it could easily be bad solder joint that connects when heated. Using same logic, try a different cord. And spray deoxit on input jacks and cord jacks

 

Had exactly this problem a couple of years ago on the same amp. Turned out to be a dry solder joint in the preamp section, and everything was fine after after a quick dab of a soldering iron.