Need help... 10-15 seconds of buzzing, then it works!

[IdealWay]

A friend of mine gave me an older Ampeg SVT-III pro because he didn't have the patience to get it fixed D sweet). I resoldered the input jack, which was the biggest problem it had, thankfully an easy fix! The only other issue is this buzzing/humming sound that occurs every time the amp is turned on. It lasts for about 10-15 seconds, during which the bass can't be heard, then swells and dissipates completely. Once the sound stops, the amp works perfectly. I'm curious what this could be and how I might fix it. I have a multimeter if that helps If it's a difficult fix, I'll just let it be since everything's fine after that initial 15 seconds, it's just kind of annoying, and I'm worried that it might be something that could lead to more problems down the road. Thanks for the help guys!

 

[johnk_10]

i've never had or even played thru one of those amps, but it sounds like that it is the preamp/driver tubes warming up/waiting to reach full voltage/stability to me.

 

[IdealWay]

i've never had or even played thru one of those amps, but it sounds like that it is the preamp/driver tubes warming up/waiting to reach full voltage/stability to me.

hmmm... never thought of that. This is actually my first "tube" head (I had a Peavey T-Max with one tube, but that didn't really count), so I'm really in the dark.

Is it normal for the tubes to produce a sound when warming up/stabilizing?

 

[johnk_10]

since its a hybrid (tube= pre/ss=power), i think that the power amp is probably coming on before the preamp tubes have a chance to warm up and pass signal.

 

[ianhiding]

The startup silence is normal. From the manual..NOTE: There is a delay during power up until the protection
relay enables the power amplifier output.

With mine, I usually just hear the fan running for about 10 to 15 seconds. Then its good to go.

 

[IdealWay]

The startup silence is normal. From the manual..NOTE: There is a delay during power up until the protection
relay enables the power amplifier output.

With mine, I usually just hear the fan running for about 10 to 15 seconds. Then its good to go.

That's the opposite of what's happening with mine; instead of silence I hear a buzzing sound, which I guess is the tubes warming up.

I'm wondering how I can make it so there is "a delay during power up until the protection relay enables the power amplifier output." ???