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Hi guys new to this site, looking for a little advice. I have a 333 212 combo that I am trying to diagnose. It powers on and everything appears to work fine, but I am getting very little sound. I literally have to crank the master up all the way to get a little noise out of it. I tried to bypass the preamp by plugging into the effects loop. This gave me nothing but some popping noises when strumming. Also get a hum and pop when the effects loop is switched on.It seems to me that the preamp is working as I hear some noise, but the power section is not amplifying the sound. This amp already has the power transformer wires soldered directly to the board. I went thru and cleaned the paint from the chassis at the grounding points to rule that out. Also looked the board and capacitors over well and all look fine. The fuses are all good as well. Did a little voltage testing on the power side and everything seemed like what it should be. Trying to find a local shop to test the tubes for me, as they are the original bugera tubes. Any help would be greatly appreciated.
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What are your voltages for V1a,v2a,v3a,v4a, v5. Voltages with tube in the sockets and with the sockets no tubes.Originally posted by bwheat View Post
Thanks,
nosaj
Schematics herehttp://bmamps.com/Schematics/Bugera/...20333%20xl.zipsoldering stuff that's broken, breaking stuff that works, Yeah! -
I will get some exact numbers for you, when I had it open last I measured the voltage out of the tubes to the output transformer and it was between 425 and 450. I will get the exact voltage though. The red which goes to the output transformer was in the same range.Comment
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Alright, I got some measurements,
Without tubes----Pin3/plate, v1 492, v2 492, v3 495, v4 494
Pin4/screen, v1 488, v2 489, v3 491, v4 491
pin5/grid, v1 41, v2 41, v3 41, v4 41
Pin8/cathode, v1 0, v2 0, v3 0, v4 0
With tubes-------pin3, v1 445, v2 447, v3 447, v4 449
Pin4, v1 444, v2 443, v3 444, v4 445
Pin5, v1 -37, v2 -37, v3 -37, v4 -38
Pin8, v1 0, v2 0, v3 0, v4 0
Valve 5----without, pin1 439, pin2 0, pin3 0, pin6 438, pin 7 0, pin8 0
with, pin1 298, pin2 36, pin3 80, pin6 308, pin7 48, pin8 81Comment
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Those readings seem ok.
How about if the reverb is turned up and the tank is 'agitated'; do you get the normal clang?My band:- http://www.youtube.com/user/RedwingBandComment
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This amp has digital reverb, no springs. I did notice that a few of the preamp tubes have some white buildup at the bottom around where the pins go thru the glass. I found a local shop that does have a tube tester, waiting to hear back on whether not they can test the 12ax7's and 6l6gc's .Originally posted by pdf64 View PostComment
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It looks feasible to apply a signal to the reverb return, so give that a go.
Do the Vdc on IC1 look ok, ie 15V on 8, -15V on 4, 0V on 7 and 1?My band:- http://www.youtube.com/user/RedwingBandComment
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I will do the test on Ic1 , as for supplying a signal to the reverb return I am not 100 percent sure what you mean, like actually attach a 1/4 jack to that circuit so that I can hook a guitar up up to it, or by jumping the signal from from somewhere else on the board?Originally posted by pdf64 View PostComment
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Whatever works and is simplest to implement, eg tack in a link wire from the normal input jack socket, fx return, etc to the reverb return.Originally posted by bwheat View Post
Anything to get a signal to the power amp, bypassing the relays and the other stuff that could go wonky.My band:- http://www.youtube.com/user/RedwingBandComment
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While looking for a place to tap into the reverb I found quite a few differences in the 333xl schematic and what my 333 non xl has. I emailed bugera to see if they have the actual schematic for this model. Waiting back on that. I am getting the tubes tested on Monday. there is an x44 2 pin connector that runs to the power side, it is the closest to the reverb controls, but with the board still bolted in place I can't really see the traces to verify that the reverb circuit is connected to it. Going to find a different type of lighting to see if I can make it out better. These black boards are kind of hard to see the traces from an angle.Comment
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Got a message back from bugera. This place has the worst customer service ever. Basically just said that I am not allowed to repair it myself and it has to be taken to an authorized dealer for repair, and that they can't release anything, or even sell parts. hoping I find a bad tube.Comment
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Behringer has never shared schematics, except with authorized service centers, and we had to sign non-disclosure agreements.
many companies do not sell parts directly to consumers, they rely on their dealer network to handle that. yes, on the other end of the scale is Peavey, who gives schematics to anyone, and wioll sell parts to anyone. You can't call Fender for a part, nor can you call Ford or GM in Detroit fora part.Education is what you're left with after you have forgotten what you have learned.Comment
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I can actually buy the parts for gm or ford though at their dealership, and get acess to all of their repair imformation. I happen to know a little something about that industry, my specialty is automotive electrical diagnostic and repair. They specifically will not even offer you the part even thru their authorized dealer like others companies will. I can get a full schematic on a 2017 50k dollar product but not a 2011 product that is worth 200 bucks. I am well aware how this works. I was just venting a bit.Originally posted by Enzo View PostComment
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Try swapping the PI tube with one of the preamp tubes. They're all 12AX7, right? I'm curious if the nature of your problem changes...
I read about a guy who had low volume on a 333XL and it turned out to be a problem with the PI tube.
Also, look for burns on the molex connectors. Also a common 333XL issue.Comment
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