Symptoms of Deteriorating Preamp Tubes

[B-string]

You very well could have a corroded effects return jack (happens more with unused jacks). Try a short instrument cable , one end plugged into the effect send and the other end in the effects return. If the amp then behaves normal the jack's internal switching needs to be properly cleaned.

[pshep68]

Originally Posted by pshep68

Occasionally, the green EQ light come on and goes off accompanied by a loss of volume ... and the EQ button is not engaged. I don't know if this is a part of the problem.

Turned on the amp tonight and heard a craclking noise and could see blue sparkes in behind the power switch. Thought I saw a tiny puff of smoke ... smelled smoke for srue.

[nashvillebill]

Time for a visit to a tech,do not attempt to play this amp until it's repaired.

[pshep68]

I removed the cover, with the unit unplugged of course, to see if I could see any scorching. Everything looks fine. Is it o.k. to turn the amp on (without cabs & bass) to see if the tubes look o.k.?

[B-string]

NO! Take it into a tech! If you lost a power supply cap and you turn it on again you could very well cost yourself hundreds more in repairs.

[pshep68]

I'll keep you posted. Thanks for all your help.

[B-string]

Best wishes for an inexpensive repair. Looking forward to the outcome.

[pshep68]

Just an update on my Ampeg 3 Pro ... it is on it's way home from a visit with the tech as I type. Two 12ax7's needed to be be replaced and there was a couple of issues with the power switch. I can't remember the specifics, but I will post more regarding the power switch when i get a look at the receipt.

[pshep68]

With regards to the power switch, it was replaced. Just a quick question...when turning on/off the unit should the green light for the eq flicker?

When I am setting the gain, the red peak light comes on between 12 and 1 (while playing the loudest note) where as before, with the same settings I could get the gain up to almost 3 before the peak light comes on.

[JimmyM]

Originally Posted by pshep68

With regards to the power switch, it was replaced. Just a quick question...when turning on/off the unit should the green light for the eq flicker?

Can't remember but wouldn't be surprised if it should. Wouldn't worry about it either way, though.

When I am setting the gain, the red peak light comes on between 12 and 1 (while playing the loudest note) where as before, with the same settings I could get the gain up to almost 3 before the peak light comes on.

That means it's fixed. You want your peak light coming on at that point so it gives you room to crank the gain and get some preamp grind if you want it. And really, that light should be lighting up pretty good before it starts to sound dirty. That's not a light to indicate clipping, only level, and you have a good bit of leeway with it to light it up pretty solid and get some balls out of it before distortion sets in.

Glad you're back in business with it!

[pshep68]

Originally Posted by pshep68

Turned on the amp tonight and heard a craclking noise and could see blue sparkes in behind the power switch. Thought I saw a tiny puff of smoke ... smelled smoke for srue.

That makes me feel better. I appreciate ur comments.