333xl infinium problem

[damus]

Hi all,

I have a bugera 333xl infinium, recently it stopped working all together all the lights flashed and I turned it off, when I turned it back on none of the lights would come on except the power tubes and the pre amp tube that was on the same board. I left it on for a little bit then the power tubes went out as well.
I replaced ALL the fuses in the amp and it turns on fine now except the power tubes and that 1 pre amp tube that's on the same board, its like that whole board isn't getting power? I bought about 12 fuses and I have replaced them all so many times that it cant be a fuse problem, I also changed all the tubes as well but just cant get it to work.
I am thinking when the amp wasn't working and the power tubes where that I may have done damage somewhere possibly?
The amp is a complete replica of the peavey JSX, I have installed a resonance knob and have the schematics but I just don't know where to start...
Can anyone give me any advise?

Thank you,
Damus

[Steve Conner]

Some people reported problems with the connectors on other Bugera amps. The wiring plugs into the circuit board with several multi-pin "Molex" connectors similar to the ones on a computer power supply. These can develop bad contacts. Most commonly the contacts carrying the heater current from the power transformer will overheat and burn up, causing the tube heaters to go out.

So, unplug the connectors and check for signs of discoloration and burning.

[damus]

I think since the infinium version they started hard wiring most of those connecters, The ones that I can remove all look fine, I have pulled it to bits and put it together during a search for a component that looks blown fried or even slightly different to other components but there is nothing obvious. Everything looks in great shape =/, I find it weird how the whole board has lost power without any obvious indication. It makes me think that the fuse that powers that board is different or something, its doing my head in...

[damus]

After going through the original fuses that where in there I have noticed that 1 of them says 10AH instead of the usual 1AH..... Could it be possible that the 10AH fuse is the one that powers that board and the 1AH's I am "attempting by stupidity" to replace it with are just blowing right away without me noticing?
Also is there anyway I can track down or if anyone knows which fuse on the main board powers the power tube board?
Help appreciated in advance.

[Steve Conner]

Do you own a multimeter and know how to check a fuse?

[Jazz P Bass]

I would think that the 10AH fuse is for the heater circuit.
A 1 amp fuse will not cut it.

[damus]

I do have a multimeter and a capacitor meter but they are at my bands house atm.

Based on a conversation Enzo had with some other dude about a 333xl combo amp a while back I think its safe to assume that the 10AH fuse is meant to be in the "F4" position. Other random strings of infomation say that the heater circuit is the one closest to the front of the amp. I will cross refrence the 2 bits of infomation and if it matches up I will chuck in a 10AH fuse into that spot.
If that doesnt work I will be a little crazy and probably start swapping them in and out chromatically. My gut tells me that this is pretty much going to work so I thank you all heaps for the help.

It's kind of proving to be the nature of the beast that if you want a tube amp you have to expect them to break and be ready to learn how to fix them.

[Steve Conner]

No, don't just go putting a 10 amp fuse in random holders. That's the electronic equivalent of poking Murphy's Law in the ass with a stick. Spend a little effort to figure out which fuse holder is for the heater circuit. The PCB traces to it may well be very thick. The fuse value may even be printed right on the board. At least one end should show continuity to the heater pins on the power tube sockets. Both ends, if some tubes are plugged in.

[damus]

Just for closure, the F4 matched the position that I was advised was the power tube heater circuit and I put the 10A fuse in it and the amp is now working great again.
It's hard to say what caused the original fuse to blow in the F1 position being that all the previous power tubes I had in it are still working and there was no power surge or short from the GPO at the wall or with a power board (even if there was I beleive the fuse in the back should have gone, not one of the internal ones). I did recently put a quad of 6l6gc's in so perhaps one of the power tubes is playing up, which seems strange for the highly rated winged c 6l6gc's. After everything broke though I have reverted back to the original el34's.
Also I could be crazy but normally the stock tubes sounded horrid but it seems like after I changed all the 1ah fuses with 1.6ah fuses the amp actually sounds noticeably allot better and I have never had the amp sounding as good as it does right now and I find that quite weird that the bugera el34's are sounding better than winged c 6l6's.....?
Thank you all for you help.

[xtian]

No, don't just go putting a 10 amp fuse in random holders. That's the electronic equivalent of poking Murphy's Law in the ass with a stick.

This made me laugh. Murphy's Ass Poker.