Bugera 1960 only runs on 2 tubes

[Jerry_C]

Hey guys, I'm new to the group and have an issue with my Bugera 1960 head. I've been using and loving it for about 9 years. Suddenly 2 days before a show as it were, it crapped out. Power but no sound. After taking it apart and checking things I noticed I could hear what I was playing in the output transformer. I don't mean just noise, I could hear the chords I was playing, in a freaking transformer. This was a new one to me. Like a very weak busted hand held radio speaker. Was very low but it was there. I ended up finding 4 fuses in the output stage, 2 of which were blown. I replaced those and as soon as power was turned on, one of them would blow. So I tried running the amp on just 2 tubes and it worked fine. I cranked it up and no problem, other than running at half power. and it didn't matter witch tubes, 1&4 or 2&3, it still worked fine. Could the problem be in the output transformer? There was no swelled or blown caps, no burnt resistors, and no burned electronic smell. Just that weird playing sound in the OP transformer (No speaker plugged in) and that one fuse that keeps blowing. BTW, I ran tubes 1&4 in sockets 2&3, and tubes 2&3 in sockets 1&4 and and again thins were fine. To summarize: No speaker cab attached, I can hear guitar playing IN the output Transformer, and 1 fuse blowing when I try to run all 4 tubes. Could the output transformer be the problem?

Thanks for any heads up on this one.
Jerry

 

[Blix]

1 or two of your tubes are blown. Hearing the sound from the output transformer is perfectly normal. :)

I have a 1960 Infinium, it eats an EL34 once in a while, running at 10 for hours takes it's toll.

 

[6CA7-A]

 

[Elf]

i don’t have a variac and I think you would need one to trace the correct voltages plus the service manual. So I would take it to a tech.

Edit. I remembered looking at this Interesting video of someone that knows what they are doing looking for a similar problem.

 

[RaceU4her]

Are you aware of the risks of electroshock from amps that are not plugged in…and also the consequences of running an amp without a load?

was gonna say, if it wasnt blown up before it probably is now

 

[Orvillain]

Do NOT play a valve amp without it being connected to a load - either a speaker, or some sort of dummy load, or loadbox. You will destroy the output transformer.

If it is working with two tubes, get through the show with that. Then take it to a tech.

 

[Jerry_C]

1 or two of your tubes are blown. Hearing the sound from the output transformer is perfectly normal. :)

I have a 1960 Infinium, it eats an EL34 once in a while, running at 10 for hours takes it's toll.

I swapped all the tubes in every configuration. 2 in center sockets then in outer sockets. Then the other tubes in bot inner and outer sockets. The all work fine, as long as it's only 2 tubes. The minute I install all 4 one of the onboard fuses blows.

 

[Jerry_C]

 

[Jerry_C]

I can fix it.

 

[Jerry_C]

i don’t have a variac and I think you would need one to trace the correct voltages plus the service manual. So I would take it to a tech.

Edit. I remembered looking at this Interesting video of someone that knows what they are doing looking for a similar problem.

I have 2 variacs but no shcematic.

 

[Jerry_C]

i don’t have a variac and I think you would need one to trace the correct voltages plus the service manual. So I would take it to a tech.

Edit. I remembered looking at this Interesting video of someone that knows what they are doing looking for a similar problem.

That's some good information but still the key is having that schematic.

 

[Jerry_C]

Are you aware of the risks of electroshock from amps that are not plugged in…and also the consequences of running an amp without a load?

Quite aware. Took an electronics correspondence coarse in the Army. Even did the "TV VCR repair coarse at home. (What a joke). But yea, I'm well aware and quite cautious. I HATE getting shocked. It makes me make up a whole new vocabulary of bad words.

 

[Jerry_C]

Do NOT play a valve amp without it being connected to a load - either a speaker, or some sort of dummy load, or loadbox. You will destroy the output transformer.

If it is working with two tubes, get through the show with that. Then take it to a tech.

We did just that. Ran on just 2, which is still ear shattering loud. I just need to get her fixed because if the other 2 go, I'm out an amp. Well I have more, just that's my favorite. Still have my 100w 34 yr old Crate head. All solid state but she still screams.

 

[Dave Lewis]

I’ve had one since new bought from Thomann back in August 2022 and it’s still going great on all the original tubes
It’s not used that regularly but when it is Mainly by my mate for a summer BBQ bash on his land in the middle of nowhere every year It sounds great
It fell backwards off a Marshall 4 x 12 cabinet once a few years ago and no damage
I have used it with my Two Notes Torpedo Captor X box at home because it’s not a true 150 w load.