Bugera 333xl-212 big problem

[Enzo]

Standard service procedure on any BUgera amps that have not been direct soldered at the factory is to clip off the Molex connector and solder the wires on the pins direct. The Molex connector is underrated for the heater current on the transformer connector. Factory service bulletin to that effect.

[iamomega]

Hi everybody,
mine died too (6262) - the same problem. I had an amptech solder it and the amp stage works again, but now the sound is a different one: it is very microphonic with very strong feedback. The amp is useless. What could be problem and what do I have to do? Could the tubes have been damaged? Do I have to retube the whole amp or just the preamp tubes or the 6l6s? Retubing would cost me something around 120 euro . But it would be the better case if itīd solve my problem. I hope it is not something more serious. I donīt know what to do, please help.
Greetz
Rado

[chipprogr]

Simple problem - and fix. you have a preamp tube that simply doesnt "behave" well in a high gain stage. You can isolate the tube by turning on the amp with access to the tubes and turn up the volume to a point just before it starts to squeal. thump the tubes gently with your fingernail and the microphonic one will stand out like a sore thumb. You can either change out just the 1 tube, or rotate it to a non critical other tube socket.

Good Luck- Eric

[Sloan]

This is common anywhere your sending high voltage/current through a molex, it's just not a good idea. Your best bet is to cut off the connector, unsolder the pins from the board and solder the wires in their respective places on the board. Be careful, all the heat generated when the molex failed can cause the tracings on the board to lift up a bit.

Here's a pic of a Bugera 333xl I just did this too, looks sloppier than it is.

[pittsville]

A Thermistor Fell Out on Mine

It's on the little board that the power cord plugs into.

The amp died. I went to check the molex connector and it had already been bypassed by the factory.

I took the little circuit board off that the power cord plugs into, and noticed that a component appeared to be missing. I shook the chassis and the part fell out from under the main board. It's a round green thing. There are a few of them on that board. This one was R3.

How they managed to make two bad solder joints on one component is beyond me. I soldered it back and and it started working again.

[Enzo]

The part got hot and weakened the solder.

[pittsville]

I believe it did. I read up on that part, and it's supposed to heat up as part of it's function.

There wasn't a whole lot of solder on either side of it, for something with leads as big as the part had.

The soldered side of the board faces up, so maybe it might be a good idea for anyone working on the molex connector to take a look at the little board and see if any of the solder joints look suspicious while they have the chassis out of the cabinet.

This amp is only a little over a month old, and I was disappointed at first to see that the factory had already bypassed the molex connector, by soldering the wires directly to the pin and heatshrinking the joint, so I knew I probably had another problem.

I didn't see the thermistor at first because it had slid under the main circuit board. I sure didn't expect to find anything like that but I'm glad I did.

[Enzo]

They are not the only people who have thermistors fall off.

We are instructed to hard wire those Molex connectors on any Bugera amp we see. They hard wire them at the factory. The early ones used the connector and ther were too many failures. Don;t be disappointed, that direct wiring is a good sign. it is an engineering change, not a repair.

[pittsville]

I was only disappointed about the direct wiring because I was hoping that the problem with the dead amp would be the molex connector!

And I was glad that the thermistor fell completely out, because otherwise it could have been an intermittent problem that came and went at the worst times, and I might never have found it.

I'm not complaining. We love the Bugera 333XL. I posted this so other guys who have problems would have something to look for if their molex wasn't burned, or was already bypassed, and the amp still didn't work.

[Enzo]

Actually of you had posted that your amp completely lost electrical power intermittantly, that thermistor is the first thing I would have suggested. I look at those on any amp that uses them. And that is the most common warranty repair I do to those amps.

[raynman]

Bugera 333XL 60htz buzz

Hey,
I have a 333Xl combo for a little over a year now. I haven't used it very much (thanks to our lovely economy). In the last month or so I noticed on 2 occasions at rehearsal after it was on for about an hour it started to produce a 60 htz hum or buzz.
Now it does it every time I turn it on. It is proportional to the volume level. If the volume is all the way off the hum goes away with it. It does it on every channel.
The amp still amplifies and sounds normal but has this annoying buzz that won't go away.
I verified that the Melting Molex connector had been hard wired (at the factory.)
I swapped out all of the power tubes. (with used El34's). I swapped out the pre amp tubes one by one, I tried a different cab..no luck.

I took a look inside and didn't notice any burnt wires or components.
I checked the solder joints at the tube sockets and they seem ok.
I didn't remove any of the boards to look under them.
Does this sound familiar to anyone?

[Sloan]

Since the hum goes away when you turn down the volume, it's probably somewhere in the preamp, which is good since preamp stuff is usually not too difficult to troubleshoot.

Check the solder joints on your input jack and all your potentiometers, while you have it open, go ahead and clean the pots with some no residue electronics/contact cleaner. Also, go ahead and clean all jacks in the amp with contact cleaner, I usually clean all this stuff before getting down and dirty diagnosing a problem since dirty pots and jacks are typical problems.

You could have a preamp tube problem, but since you swapped them that seems unlikely, but if you have known good tubes, try them anyway.

[Enzo]

Before you do anything inside the amp, turn the volume control on the guitar down to zero. Does the hum remain or go away? if it goes away, that means the guitar is picking up the hum.

[iamomega]

Hi everybody,
mine died too (6262) - the same problem. I had an amptech solder it and the amp stage works again, but now the sound is a different one: it is very microphonic with very strong feedback. The amp is useless. What could be problem and what do I have to do? Could the tubes have been damaged? Do I have to retube the whole amp or just the preamp tubes or the 6l6s? Retubing would cost me something around 120 euro . But it would be the better case if itīd solve my problem. I hope it is not something more serious. I donīt know what to do, please help.
Greetz
Rado

So.... This is what i did to solve my problem. I found a tube in the preamp which was clearly microphonic and I was very glad about that. I bought another 3 12ax7 tubes (each from a different manufacturer). I replaced the "bad" tube and nothing happend, the new one went immediately microphonic in that position. The same went on with the other tubes. So I took it back to the amp tech who tried to do his best without having the schematic. He swapped the tubes, did this and that (Iīm not sure exactly what he did and I think nor did he, because Bugera painted the electronic parts in the inside so they wouldnīt be recognisable and thus it wouldnīt be possible even to draw a scheme which the amp tech could have worked with). After that the amp is more or less OK again, I think it is a little bit more squealish than before.
Though I like the amp I just donīt understand the Bugera policy. As far as I know thereīs no way circuits could be pattented or copyrighted so even if stolen from Peavey... And if lets say Peavey wanted to get the Bugera schematic it would have done it by now. I know many guys around forums like this do have it!!! So whatīs the problem? I hope somebody will finally anonymously publish the schematic...

[raynman]

Enzo,
The guitar volume has no effect. It buzzes without the guitar plugged in.

Turning the effects loop on with the clean channel seems to lower it a little.
Turning the effects loop on with the crunch/lead channels seems to make it worse.

The amp works and sounds exactly the same. There is just this buzz that came out of nowhere. You can drown it out as you are playing.
It gets louder with any volume increase. It goes away completley with the Master off
I turned every knob on the amp off. It still comes back as you turn up the Master volume.
Thanks for the reply