Ampeg SVT 3 Pro Problems...

[Gardo]

Just wandering if anyone has ran into this issue: I took my SVT 3 Pro in a while ago when I noticed a strange, annoying, crackling sound coming from my amp. Much like a battery going out, or tube, or something like that. I made sure that it was not an issue with my cab first, then I got in contact with my tech. A few things jumped out to him, such as, the peak light rarely lighting up, and lack of power, that had him assuming the problem to be within the pre-amp. When I took it in he replaced all the tubes, cleaned all of the pots, and that seemed to fix all said problems. When I got it back, it truly did sound like a new amp... For a while... While practicing the other day, it started to make that awful crackling sound again. As you can imagine I was extremely upset. I checked all my cables, made sure the D.I. worked, e.t.c. Then I noticed that the input jack on the amp was a little loose. I tightened the jack, and didn't have a problem the rest of the night.

So, I was just curious if this has happened to any other SVT 3 Pro users here. Or if this is a known thing for this amp? I truly didn't think that a loose input jack was capable of such an awful crackle, which would be suited more towards a tube going out, or this BIAS I have read so much about now. Should I still be concerned about my amp and seek further assistance from my tech, or could my problem be solved? ??

 

[fauxfighter]

I have similar probs with my SVT 3, the crackling at low volume etc, but also noticed that the tube gain makes little or no difference to the sound, I've not had mine long so not that familiar with it, but is this a sympton that the Mosfet Bias needs adjusting?

 

[Foz]

Ya might try cleaning the send return fx loop jacks... if that don't work consider changing the tubes - especially if you bought it used and they are quite old - maybe a new set of JJ's, they are pretty good tubes and reasonably priced. If its still acting up get it biased.

 

[DALE GINGERY]

I know it flat sucks, It took me awhile to figure it out and now after 2 different repair facilities and replacing all the tubes in it and they still have not fixed it, now I have to ship this thing 1200 miles to a shop I can trust, but they said the same thing. The bias control is so touchy the shaking from the bass let alone if you bump it in transport can knock it back out so I have elected to wait till they can find an upgrade for this issue. Thank God for the Hartke backup.

 

[Foz]

put some purple nail polish on the twiddly bit once you got it adjusted

 

[DALE GINGERY]

Thanks that is a great tip, if I can get the repair shop to do it before they close it up

 

[DALE GINGERY]

Foz, I did it, not the right way but I was very careful in adjusting it and I got it. I didn't have any of the equipment to do it, but I made slight movements in it till the buzz was gone and played through it at about 1/4 volume for an hour and it seem to do just fine. Amp didn't get real hot and still sounds clear so I put a little dab of nail polish on it to lock it in that position, thanks again brother. (I was just about to buy a new amp, till you and this forum shed some light on this issue)

 

[Foz]

well alright then.

 

[agedhorse]

I strongly encourage folks to either do it the correct way with the proper equipment, or have is done properly by a repair shop. Too many reports of folks not doing it the right way causing major damage and it happens virtually instantly.

 

[rickdog]

What he said ^^^. I've adjusted mine, using a DVM and a jeweler's screwdriver. If I remember right, I turned the screwdriver by holding it down with one hand and gripping it with a pair of pliers to actually turn it because that way I could move it very small distances.

I kid you not - rotating the pot by a distance about equal to the thickness of the screwdriver blade made a big difference in the measured voltage. Scary. It was easy to see how a tweak too far could happen, and let out the magic smoke.

I think you were very lucky adjusting it by ear.

 

[agedhorse]

There is nothing worse (or more costly) than repairing something that was ruined by a repair attempt.

 

[DALE GINGERY]

I totally agree, I was a risky move, I even hesitated. But when your amp has been in 2 different shops for 2 and a half months and your gigging all the time and they still have not fixed the issue and the next step was to ship it to ampeg that refuses that they have these issues, not to mention I had to drive to these repair facilities that in total was about 450 miles, yes I had no other choice. And yes the two shops were supposed to be ampeg certified.