Bugera 333XL Infinium Issue

[nickb]

Hold on. It's a year since the last post. How long have those new EL34's been in there?

There are a ribbon cables that go from the power board to the bias controller. Any poor connections on that can cause havoc.

Here is a schematic of the tube board and bias PCB I drew up some time ago. There may be errors or be incomplete as I ran out of time to check it. Maybe it will help a little.

Infinium.pdf

PS: This schematic is from a Bugera 6262. I think 333XL is similar, if not the same in this regard.

[g1]

Still like to know the exact fuses you are using, and if they have all been the same type.

[Pedro Vecino]

I don't know anything about the Bugera automatic bias circuit but in a G20 that rejected the operation with new tubes I found an open resistor and an inflated capacitor. Replacing them worked again.

[stevenrb718]

Still like to know the exact fuses you are using, and if they have all been the same type.

Oh that's my bad g1, I didn't see your posting. I've been using 2A slow burns that I got from tubesandmore.com. I'm not sure if they're branded but they are in fact the same fuses I've been using throughout the diagnosis.

[doombass]

Oh that's my bad g1, I didn't see your posting. I've been using 2A slow burns that I got from tubesandmore.com. I'm not sure if they're branded but they are in fact the same fuses I've been using throughout the diagnosis.

One EL34 alone takes 1.5A current draw on the filament supply. If your power supply is the same as in the above provided schematics you are supposed to fit a 10A fuse. A 2 A fuse can withstand supplying the PI tube and one power tube but that's about it.

[nickb]

One EL34 alone takes 1.5A current draw on the filament supply. If your power supply is the same as in the above provided schematics you are supposed to fit a 10A fuse. A 2 A fuse can withstand supplying the PI tube and one power tube but that's about it.

There's a 2AT fuse in the HT supply. I expect it's that one. A 2A fuse would never work in the heater supply.

[g1]

There's a 2AT fuse in the HT supply. I expect it's that one. A 2A fuse would never work in the heater supply.

This is my point. It's not working. Unless a bunch of tubes are pulled, then it works til there's more than 2A draw on the heater line again, then it blows.
In post #6 he specified that it was F4 that blew. If he were now talking about a different one, I think he would have mentioned it.
F4, at least in the non-Infinium needs to be a 10A fuse (fast specified).

I guess we need to verify that F4 in the Infinium is the heater fuse.

(edit: re-reading all the OP's posts, it's obvious we are talking about the heater fuse. Needs to be replaced with proper value)

[stevenrb718]

I was in contact awhile back with Bugera tech support about the fuses. "Thanks for contacting us!
Fuse F1-F4 are all 2 amp slow blow fuses. "

That's the only reason I was using a 2A fuse in F4 to begin with, not that I would know of a proper value without the schematic. Did I just get bad information?

[The Dude]

From available knowledge and without a schematic, yes...... you got bad information. The filament fuse should be 10A as g1 said.

[Jazz P Bass]

Here is a crop of the 333XL power supply.
F4 is stated as 10A Fast Blo.

[The Dude]

I was in contact awhile back with Bugera tech support about the fuses. "Thanks for contacting us!
Fuse F1-F4 are all 2 amp slow blow fuses. "

That's the only reason I was using a 2A fuse in F4 to begin with, not that I would know of a proper value without the schematic. Did I just get bad information?

Was not the original fuse marked? Was it missing? I'm not sure why you wouldn't just look at the fuse that was in the unit and use an appropriate replacement?

[stevenrb718]

Was not the original fuse marked? Was it missing? I'm not sure why you wouldn't just look at the fuse that was in the unit and use an appropriate replacement?

The fuse that was in it when I got it from a friend was a 2A. He was getting the no sound and check tube LEDs. Obviously he must've changed the F4 fuse with an incorrect replacement. I don't know what caused any of the issues to begin with, or if he just somehow blew the fuse and put the wrong value in. I contacted Bugera and asked about the fuses when I kept popping the 2As for what seemed like no reason. They told me 2A for all 4 fuses (thanks a lot), so I also used 2As. For all I know I'm no closer to determining what the original issue even was.

[The Dude]

It's always more "fun" when a user tries to fix an amp himself.
In this case, I'd have a close look at all of the other fuses and make sure they are the correct value. You never know- there could be a 10A fuse in a place where there's supposed to be a 2A fuse. Somebody may have mixed them up.

[stevenrb718]

It's always more "fun" when a user tries to fix an amp himself.
In this case, I'd have a close look at all of the other fuses and make sure they are the correct value. You never know- there could be a 10A fuse in a place where there's supposed to be a 2A fuse. Somebody may have mixed them up.

Yeah that idea had already dawned on me. I'll have to check that out in the afternoon. Would the Infinium version have the same fuses as the non-Infinium, because that schematic piece of the power section is definitely showing 2 other fuses as 1As? Could the Bugera contact have been *that* wrong? (don't answer that)

[Jazz P Bass]

F1: 2A FB: High voltage supply.
F2 & F3: 1A SB: Dc heater supply.
F4; 10A FB: main AC heater supply.
All values seem reasonable.

Bugera was pulling your chain.