Bugera 333 212 combo, very low output

[Jazz P Bass]

There is a thread around here for a BX1200 Behringer amp..\ Look it up. Jazz P Bass posted your schematic over there, I assume by mistake. Go get it.

http://music-electronics-forum.com/a...242224-333.zip

[Enzo]

I never know which pin is which on JFETs, there is no standard. One is ground, another goes to the two resistors, and the remaining one is the gate. An ohm meter will sort those out.

If you got half a volt there, and no DC voltage on the other two, then that was the gate, and I suspect that part. Try removing that transistor and see if the amp wakes up.

[bwheat]

Rechecked the voltages on the 3 pins, had basically none on the other 2 , so I removed the transistor and now have full volume. It definitely doesn't sound 100 percent correct, has some popping and volume inconsistencies, kind of fades off a little bit after hitting a note, but has full power. Going to order a new part tonight, any brand that you might reccomend over others? The effects loop doesn't make a loud popping noise either, it does give it quite a bit of a boost when kicked in.

[Enzo]

The sole purpose of that part is to mute the amp briefly when changing channels. If you do not get loud noises as you channel switch, then you could leave it out.

Brand? It is just a transistor. get it from a real parts house, not ebay.

[bwheat]

I hooked my other amp's line out up again to the effects return again, and the issue with the volume cutting out is present when using the preamp from the other amp, but fine when the effects send is ran into the front of the other amp, so sounds like likely something in the power section causing that. Going to have the power tubes tested on Monday, maybe go thru and check the grounding spots. It has a little corrosion on the poles that the boards mount to. My plan when I get it running properly was to take the boards out, clean up all the mounting posts, clean all the dust and debris out and clean the pots.

[bwheat]

Got a little more free time to mess with this thing. Did a little messing with it and got it sounding real good, except for the clean channel, it has a rather rattly distorted sound to it.

[The Dude]

I'm wondering if you're hearing crossover distortion. Have you checked bias? Another possibility: Have you tried the speaker(s) with a known good amp or the amp with known good speaker(s)? Could be a bad speaker or speakers. Using the distortion channel could easily mask either of those sounds. The "rattly distorted sound" could be there always and only noticed on the clean channel.

[bwheat]

It resembles the sound of a blown speaker, but just sounds so good on the gain channels, even with the gain turned down. I did hook each speaker up one at a time, and the sound comes thru both the same. I am thinking about using the line out into another amp or headphones to see if the sound is replicated. Don't have another set of speakers to try out, other amps are small practice amps. I haven't checked the bias yet, planning on making a cable to hook to the test port.

[bwheat]

Borrowed a cab and hooked it up, same thing thru that cab. Speakers are fine.

[bwheat]

I have tried recording some sound files which are wmv but for some reason the attachment manager won't let me load them on here. None of them are bigger than 5 mb.

[g1]

You can't attach wmv. MP3 or M4A can be attached.

[bwheat]

OK, I will see if this works.

[bwheat]

First video clean channel, 2nd is crunch channel, 3rd video is crunch channel with effects loop/boost kicked in, 4th is crunch channel again, and 5th is the lead channel.