#1
Hey guys, today I went and bought some JJ EL34's to put in my Bugera 6262 which comes originally with 6L6's. There is a slider to switch between EL34 and 6L6 tubes. So I put the new tubes in, set the switch to EL34, and turn the amp on. After the tubes warmed up I put the leads of my voltage tester in the RCA jack to bias the tubes. As I had the voltage tester hooked up, the amp made a buzzing sound through the speakers, then blew the fuse in the back of the amp. I tried another fuse and got the same results. I have already checked the fuses inside the amp and they are all good.

Does anybody have any experience with this particular problem? I just don't understand what the hell happened to cause this type of problem. Switching tubes should have been an effortless process.

I'd appreciate any help.
#2
i think possibly, you need to put a higher capacity fuse in your amp when you switch to a different tube set, because the EL34's use a higher amount of volts then the 6L6's...I'm not for sure this is the problem because I've only had one tube amp, which is the current amp i use, the Peavey 5150 and it doesn't have a switch to use different tube sets, but my buddy had a Mesa that was able to switch between different tubes, and I remember him saying that he had to use a different fuse depending on what tubes he used.
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#3
Could be a number of things. Try putting the bias on the coldest setting and try again. There's a small chance the new tubes are the cause as well. Sometimes, new tubes fail. Also, make sure the sockets are clean.

edit: by the way, using the test points on the amp for biasing will lead to an inaccurate bias. You need to use a bias probe.
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#4
I thought I'd throw in that I tried to put the 6L6's back in, and flipped the switch back to 6L6 and had the same results. The same thing would happen with both the EL34's and the 6L6's.

Edit: The amp also makes a buzzing noise right before it burns the fuse out (with both types of tubes.) I'm just wondering if something could have went inside the amp.
Last edited by csharp at May 23, 2010,
#6
are you sure you're reading the "voltage"?

where's the RCA jack located in the circuit? how many tubes, what kind are in the amp, and what rating fuse is it using?
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#7
I've heard of a number of problems with Bugera amps.

There's this one model that has like some clip in the back melt and all of them have it. It's some defect. I remember playing on the amp and seeing it shut off and then smoke appearing out of the back. I was like wtff. Looked it up online and found it was totally normal.. for this brand.
#8
Quote by TechnicolorType
I've heard of a number of problems with Bugera amps.

There's this one model that has like some clip in the back melt and all of them have it. It's some defect. I remember playing on the amp and seeing it shut off and then smoke appearing out of the back. I was like wtff. Looked it up online and found it was totally normal.. for this brand.

The transformer clip issue has been solved for a very long time now. Only very old production models of the high-gainers still have it.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#9
Is it possible that the 6L6/EL34 switch is dodgey? Did it feel like it switched properly?
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#10
Quote by Kanthras
The transformer clip issue has been solved for a very long time now. Only very old production models of the high-gainers still have it.


Nice to know they did something about it because that amp was freaking awesome for the price. I was pretty surprised.. then it blew.

Even if it was an easy fix, it still doesn't look good to have a defect on something you're selling.