SVT3 scratching noises?

Venom of God · #1 01-12-2013, 07:41 PM

Hey guys,
lately my SVT3 has started to make these weird *scratching* noises, even when the mute switch is engaged. Tonally any playing through it sounds the same as it always has, apart from the scratching. I want to say that I think it's an issue with dirty power or something, as I'm not long in a new house, but I have used it here before and not noticed anything strange. It wasn't doing it when I last used it at a friends house, so I'm worried it got shaken up in the car or something?

Could it be a tube issue? I think not due to it sounding the same, but I'm far from an expert. Unfortunately I don't have an interface at home right now (nor do I own a PA) so I can't test the DI.

Increasing the volume or gain does not seem to make any difference, as expected I guess since it still does it on mute.

Any ideas?

Venom of God · #2 01-12-2013, 07:46 PM

And after just turning it back on then it had stopped completely, until I hit the bright switch and it made a sound like I imagine a machine gun would sound like were it run through a high pass filter. Again, this happens regardless of whether mute is on or off. Starting to really not like this..

B-string · #3 01-12-2013, 07:52 PM

Might just be a tube that needs re-seating or replacing.

Venom of God · #4 01-12-2013, 08:36 PM

Just re-seated them then, thought that I'd fixed it as the noises were all gone, but once I plugged a lead in it started again after hitting the bright switch! Might have a play with the jack and see what happens.

It was a little messier inside than I would have expected, being a Vietnamese model I wonder if the yank amps are tidier? Lots of messy silicon work and glue spilt onto the PCB. Apart from the 12AU7 which was an Electro Harmonix (with crap stuck to it) the tubes were all Sovtek's though, which surprised me, I was expecting Chinese tubes.

Venom of God · #5 01-12-2013, 08:38 PM

Also, hitting the mute button is now creating a *pop,* like if you were swapping leads in and out with power still on. Maybe I should really leave this to a tech..

B-string · #6 01-12-2013, 08:42 PM

I always recommend to see a tech. Easy self checks done.

Jerrold Tiers · #7 01-12-2013, 10:55 PM

You might try replacing the first tube...... sounds like it may have a problem. Both the mute and bright are associated with the first tube.

Not a guarantee, but cheaper than the bench test fee.

if that doesn't do it, then it's tech time. There may be an issue with the +- 16V DC, or the "mute" jfet. The "pre" buffer amplifiers for tuner and line out might be causing an issue. Those are less likely to make trouble with the "bright", though.

Venom of God · #8 01-13-2013, 12:30 AM

Is the first tube the one closest to the input jack? I did notice that the one kind of on it's own to the right was sitting off centre slightly, and after pulling it out noticed that the little legs on it were bent. Still clicked back in properly and glows, but may be an issue?

Venom of God · #9 01-13-2013, 07:54 PM

Turned her on again just then- no funny noises what-so-ever, no matter what switches I hit, UNTIL I plugged a lead into it. All started up again then, it even makes a lot of popping and hissing when I plug/unplug the other end of the lead into a pedal even though the amp is set to mute. I'm totally at a loss; would you guys recommend I give the whole thing a re-tube (I bought it new in June 2011, it has gigged and rehearsed a fair bit in that time) or just go straight to a tech?

JimmyM · #10 01-13-2013, 08:16 PM

I'd buy one of each kind of tube in there and swap them all out one at a time until I found the culprit. Tubes almost always go bad one at a time. I can't recall having more than one tube go out at a time on me. Wait...there was one time...coincidentally it was a 3 Pro, too. But I bought it used and it was dogged pretty hard when I got it. Otherwise, they've all gone out on me one at a time. Also, don't think it's related, but would be a good time to spray the effects loop jacks out. They can corrode and cause cutting out over time. And then if that doesn't work, take it to a tech.

B-string · #11 01-13-2013, 10:07 PM

You could still have a bad tube in V1 as Jerrold Tiers suggested (make a note of his sig.) As Jimmy said your jacks could be dirty. Do the simple stuff first, if you don't have success then take it in to the shop.

Venom of God · #12 01-13-2013, 11:46 PM

Which one is v1? I just got home from the shop then with a new 12AX7 and a 12AU7 so I can try swapping them out one at a time and see if I can't find the problem!

JimmyM · #13 01-13-2013, 11:59 PM

Looking at it from the front, it's the one farthest away from you and to the left. Should be a tube chart in it somewhere, maybe on the inside of the lid? I forget where mine was.

Venom of God · #14 01-14-2013, 12:04 AM

Oh, so right up in the power amp section? Next to the 12AU7? I was expecting it to be a preamp tube! No tube chart I'm afraid, will do a Google though.

JimmyM · #15 01-14-2013, 12:14 AM

I'm sorry...you're right. Been a while since I owned one. It's the one closest to you on the far left. At least I'm reasonably moderately convinced of it

Found this gutshot just now:

Venom of God · #16 01-14-2013, 12:20 AM

I've swapped out every tube, one at a time, and none of them fixed the issue unfortunately.. might just have to suck it up and take it to a tech! Was hoping I wouldn't have to as I hate being Ampeg-less and having to use my MicroCube :P

Interestingly, the Tung-Sol 12AX7 I picked up doesn't glow even half as bright as the Sovteks that it came stock with!

Venom of God · #17 01-14-2013, 12:26 AM

I can say though that it's definitely master volume related, I usually have my Master dimed and adjust volume through the Gain knob, but when the master is down it doesn't seem to do it? This is regardless of mute being on or off..

JimmyM · #18 01-14-2013, 12:27 AM

Glow doesn't indicate anything except differing manufacturing methods so don't let that throw you. Unless it's got no glow whatsoever, you're good. Bummer it didn't work but now you have a couple of spares for when you do lose a tube.

I'd take it to the tech and tell him what Jerrold said about it word for word. Maybe it'll save him some trouble figuring it out, which results in less bench time for you.

Venom of God · #19 01-14-2013, 12:47 AM

What I have learnt from this experience is that Tung-Sol tubes are way more badass than Sovtek's! Just having the one swapped over (in V1 position) makes the whole amp sound HEAPS fatter, almost more complex if that makes sense? It also drives the pre-amp WAY harder and I can get an overdrive tone almost similar to my Agro pedal without a pedal at all! It would hardly break up on it's own before. Crazy!!

Venom of God · #20 01-14-2013, 06:26 PM

I was swapping in and out the Tung-Sol and Sovtek in V1 just for interests sake before and the problem seems to have fixed itself! I have no idea why it didn't fix it the first three times and did the fourth, but there you go. Weird.

Thanks for all the help guys, I appreciate it! Anyone with an SVT3 that sees this, I do recommend swapping out that first tube (very bottom left) also, the tone honestly is noticeably better and with heaaaps more gain. I may do a comparison video once I get my interface back! Cheers.