#1
I'll start off by saying I'm a hobbyist/recreational guitar player and to give you a sense of use, I can go weeks to months between playing and then play every other night for weeks or months.
I've owned my Valveking for almost 10 years and its been a great amp. I did have some issues about 5 years ago and ended up having to replace the pre-amp tubes. I started having problems again about 18 months ago. The amp started to pop and crackle. After some research I came to the conclusion the power tubes were going. I replaced them with a quad matched set of TAD 6L6GC-STR's, purchased from TheTubeStore.com. They sounded great! 2 to 3 months later, while playing, the amp just popped and shut off. I found the fuse blown. I replaced it and played for about 5 minutes more and the same thing happened. I did some Googling, but didn't come up with a solid solution. I'm mechanically savvy but never having worked on a tube amp before and for fear if the unknowns, I threw in the towel and dropped my amp off at the local amp shop. While there, the amp Dr. called me and said my new tubes were bad and needed to be replaced. He said the BIAS in the amp was off and that's what caused to tube(s) to go. I didn't believe him at first but, after he explained, in good detail, the logic behind the BIAS and how it needs to match the voltage from the tubes, and a quick Googling, I felt comfortable and gave the green light to fix. He replaced the 4 TAD tubes with 4 Tung-Sol 6L6GC-STR's and biased the amp for the tubes. $200 later when I got the amp back, everything worked better than expected, I was happy!
After going through a recent 4 month period of not playing, while playing the other night, the volume cut in half followed immediately by a smell of a burning something(tubes) and a very bright glow from the wall of which my amp backs to. I put the amp in standby mode and checked the tubes. Two of the four were burning up. The other 2 looked what I would consider normal. I managed to snapped a picture of the tubes before they cooled down to show what I was seeing: Picture . I keep the volume for both the clean and gain channels around 1, not very loud and was playing for about 30 minutes. I let a few hours pass and played again for 45 minutes or so and didn't have any issues. Then yesterday, while playing the same thing happened only it was the other two tubes that were on fire.
Both the repair shop and Tube Store have a 90 day warranty on the work and parts so, I'm on my own with figuring this out unless I just pay them man, again. I've tried searching for some thoughts and ideas on what might be going on but I'm coming up cold. I do not have a tube tester and don't know if the tubes are bad and need replacing. I don't have a problem paying the man to fix this again, but I'm a car/computer guy and could talk shop all day with the best on the subjects, but the inner sanctum of an amp is foreign territory and I don't want make things worse or to be taken for a ride if its something simple I can replace. What could be going on here?
#3
Quote by Will Lane
10 years with the VK? I think it is just time for you to get a new amp, friend. It sounds like the VK is just going to continue to break down.


... but its been such a good little amp.
#4
Any tube amp can be put back in shape.
The first thing you need to replace is your amp doctor.

Your tubes run $80 a quad for Tung-Sols at Guitar Center, $76 for a matched and tested set of four JJ's at Eurotubes.com. Merely resetting the bias won't usually cost an additional $120, and unless the bias is wildly out of whack, shouldn't cause issues (mostly just changes in the sound).

There may be other damage in the amp, and you need a good tech to run it down and you'll possibly have to replace the tubes again.

10 years isn't a long time with a tube amp if you're using it regularly. I've got tube amps that date to the early '70's that are going strong. But as you've no doubt found with computer motherboards, one issue can cause another, so you have to track down all the issues and make sure that it's back in shape before cranking it up again.
#5
Quote by dspellman
Any tube amp can be put back in shape.
The first thing you need to replace is your amp doctor.

Your tubes run $80 a quad for Tung-Sols at Guitar Center, $76 for a matched and tested set of four JJ's at Eurotubes.com. Merely resetting the bias won't usually cost an additional $120, and unless the bias is wildly out of whack, shouldn't cause issues (mostly just changes in the sound).

There may be other damage in the amp, and you need a good tech to run it down and you'll possibly have to replace the tubes again.

10 years isn't a long time with a tube amp if you're using it regularly. I've got tube amps that date to the early '70's that are going strong. But as you've no doubt found with computer motherboards, one issue can cause another, so you have to track down all the issues and make sure that it's back in shape before cranking it up again.


I love the amp. Its fits my style and sounds great ... albeit, when working .

I couldn't find many repair shops around my area, Atlanta, GA. The one place I went to seemed like a decent place and did deal primarily with Guitar amps. It was either him or Guitar Center and other places that just outsource the work. I prefer to deal with local shops. I suppose its possible something was missed/overlooked or I was just a victim of averages.

I feel better educated thanks to yours and a few other users input. It sucks that I'll most likely have to spend more money into something that I don't have knowledge to fix but, as long as it gets corrected in the end. I'll be happy.
#6
Make sure when you take it to the tech you mention about the two tubes hot and two cold, in a class A/B tube amp - like the VK - the power tubes work in pairs 1&4 and 2&3 (from left to right) given that you had tubes 1&2 hot with 3&4 cold, and then the opposite would point me to something happening with the push-pull power circuit. The VKs also have a texture knob that allows you to run it as a class "A" or a class "AB", which way do you normally run the texture switch?
#7
call Peavey. my VK had an issue that even a certified tech couldn't figure out. i called Peavey and as soon as i described the issue they knew exactly what it was. turned out to be some resistor that went bad. i'm guessing your VK is probably from the first batch they made which seem to be more prone to having issues.
#8
Quote by guitarsngear
Make sure when you take it to the tech you mention about the two tubes hot and two cold, in a class A/B tube amp - like the VK - the power tubes work in pairs 1&4 and 2&3 (from left to right) given that you had tubes 1&2 hot with 3&4 cold, and then the opposite would point me to something happening with the push-pull power circuit. The VKs also have a texture knob that allows you to run it as a class "A" or a class "AB", which way do you normally run the texture switch?


Prior to all these shenanigans, I had it in AB all the time.
#9
Quote by monwobobbo
call Peavey. my VK had an issue that even a certified tech couldn't figure out. i called Peavey and as soon as i described the issue they knew exactly what it was. turned out to be some resistor that went bad. i'm guessing your VK is probably from the first batch they made which seem to be more prone to having issues.

Right on man. This never crossed my mind.
#10
Quote by Buchez
Right on man. This never crossed my mind.


no problem. sometimes the most obvious thing is the last thing thought of.
#11
Quote by guitarsngear
Make sure when you take it to the tech you mention about the two tubes hot and two cold, in a class A/B tube amp - like the VK - the power tubes work in pairs 1&4 and 2&3 (from left to right) given that you had tubes 1&2 hot with 3&4 cold, and then the opposite would point me to something happening with the push-pull power circuit. The VKs also have a texture knob that allows you to run it as a class "A" or a class "AB", which way do you normally run the texture switch?

I'm fairly sure the pairs on a VK are 1+2 and 3+4. You can pull the inner or outer two tubes and it will still run at half power, which means the pairs are not what you suggest. So it does sound like a power supply issue, which is borne out by the picture which seems to show one pair redplating and the other pair with only heater current. Add a blown fuse on top of that and it sounds like the power supply is bad, and is likely to keep blowing tubes and fuses if nothing is done about it.

Additionally, the "A/AB" knob just unbalances the PI. Calling it a class control is a marketing flourish but doesn't describe at all what it actually does. It's probably not relevant here.

This needs to go to a competent tech. I would not accept "get new tubes" as an answer. The blown tubes are the symptom, not the problem.
#12
Quote by Roc8995
I'm fairly sure the pairs on a VK are 1+2 and 3+4. You can pull the inner or outer two tubes and it will still run at half power, which means the pairs are not what you suggest.


I think we are saying the same thing as the outer tubes would be 1&4 and the inner tubes would be 2&3 as I described them in my post. If you are referring to V #s from the amp schematic then I have no idea of the actual valve numbers, I was referencing position assuming from left to right you label the power tubes 1,2,3,4.
Last edited by guitarsngear at Apr 20, 2016,
#13
No, we are not saying the same thing. The pairs are, from left to right, (1 2 ) ( 3 4). Not 1+4 and 2+3 as you said.

When you go to half power you pull one from each pair, not one of the pairs entirely. The pairs are left/right and not inside/outside. At least not on the Valvekings I have worked on.

The left/right pairs are consistent with the left two or the right two power tubes redplating or not heating up, as the picture and description of the problem indicate. If the pairs were inside/outside, you would not see this left/right split in function.

Usually this would be a trivial distinction, but it is important in this case.
#14
we are actually saying the same thing, the difference is in how we are defining pairs, I define pairs as in the pairs of tubes that work together, i.e. if you run at half power you are running on pair 1&4 or pair 2&3 whereas you are dividing them based on their function in the push-pull circuitry.

That is why in my initial post I pointed out the having 1&2 red but 3&4 cold (or vice versa) would indicate an issue in the power supply because only half of the push-pull circuit would be working. We both agree on that and that to run an amp needs at least the two outer or two inner tubes, we are just classifying 'pairs' differently.
#15
I see. That's pretty confusing, TBH, since tubes that "work together" are not limited to the outer or inner sets, and you're using an already established term as literally the opposite of what it's commonly assumed to mean. Industry standard in the context of 4-tube amps is to use "pair" to mean the the sets on either half of the PI, and makes a lot more sense to me. Otherwise you aren't referring to specific tubes, right? "Pair" by your definition could be any of the following:
1 and 3
1 and 4
2 and 3
2 and 4

Instead of just:
1 and 2 OR
3 and 4.

Hence the near-universal agreement on the standard definition

So I have to take issue with your use of "pair" here as unhelpful and confusing.

In another context, like if you specified "outer/inner pair," or if you are talking about an amp with only two tubes, then your use makes sense. Here, though, I think you'll find that most people working on amps will use "pair" to mean the two tubes that share a side of the PI.
#16
Fair enough, however I didn't expect the reader to pull my definition of pair out of the air and know how to apply it, I specified valve numbers to make it clear which tubes I was referring to as pairs. Yes 1 and 3 and 2 and 4 could also be a pair but again i did specify what I meant in this context.

outer/inner pair is the same as 1 and 4 and 2 and 3.

From now on I will try to be more specific when I reference tube pairs working together so as not to upset the aficionados