Bugerra Trirec might have bad output transformer but not sure.

Jimi-C

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I have a trirec that got fried in a thunder storm while playing in the basement . I heard a loud squil just before the sound went dead as lighting struck a tree near the house and blew the breaker on the house transformer out side.
next day I tried to turn the amp on , and everything lit up but no sound was produced in the clean channel , the second and third channel produced a small sound but with out volume control having any effect .
I then connected my guitar to the return on the fx loop and had out put . my question is if my output transformer was shot would I still get out put of any kind .
I'm not that familar with electronics just basic stuff and I was wondering what else in the signal chain got fried beside the output transformer maybe in the clean channel . I looked to see if any fuses were blown , pulled them out and checked them with a multimeter none were open .and I didn't see any burn marks on the pcbs. I was hoping someone may have had a problem like this and could tell me what to check for before I take it to a shop ,
Any suggestions would be helpful .
 

Jon Snell

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Storm damage can cause untold issues. Not likely to be output transformer though, more likely a voltage surge cause failure in the circuit somewhere.
What happens when you plug a signal into the direct input or effecs return. That will tell you if a valve has failed or a semiconductor has failed by separatimg the pre amp, tone controls and power amp.
 

Jimi-C

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What happens when you plug a signal into the direct input or effecs return.
I get sound when I plug my guitar into the effects return , and I replaced all the tubes to make sure that was not the cause ,the first one look a little funny it was a 12ax7A , I would not be surprised if some kind of power transistor burned out . I can't find bugerra trirec schematics so I don't know exactly where to start testing , have to go by the basics for this one , if I can locate the problem it will save a bundle on labor charges , I don't want to spend more on repairs than what the amp is worth. it's a nice amp , I would like to fix it.
 

Jon Snell

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That means the power section is good. Work your way back towards and through the tone control section.
It uses TL072 ICs everywhere.
Pins 1 & 7 are the outputs of the ICs. If you have signal on pin 2 or 3 then there will be signal on pin 1.
If you have signal on pins 5 or 6 you must have signal on pin 7. If you have no Oscilloscope, take it to someone who has.
Please look at the attached for 072 and 074 types.
 

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Jimi-C

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Thank you @Jon Snell , I will do my best , I don't have an oscilloscope , is it posisble to test with an ohm meter ? or here is a low cost oscilloscope on amazon I could purchase for testing ( STARTO Handheld Digital Oscilloscope Kit 2.4” TFT with BNC-Clip Cable Probe and Power Supply) I'm not sure it has all the functions I need for testing , maybe you could take a look at it and let me know if it will work . keep in mind I'm a novice at electronics so I might ask a lot of questions , never used an oscilloscope but I understand it's purpose .
 

Jon Snell

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You could make a probe consisting of a little amplifier a ground clip and a meter lead as a probe.
As you touch the pins you will hear the signal. See attachment for a schematic I just designed.
Many oscilloscopes are available on fleabay and amazon etc.
The more you pay, the better the specification.

Have fun building and this probe can be used for lots of things.
 

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Jimi-C

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@Jon Snell Got It . I willl order parts and build it ,
Thank you for all your help , I'm not an electronics engineer but I love to tinker :thumb: I manage to find some schematics on the amp , rev I , thats whats on the pcb . that TL072 & TL074 are those op amps ?
 

Jon Snell

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@Jon Snell Got It . I willl order parts and build it ,
Thank you for all your help , I'm not an electronics engineer but I love to tinker :thumb: I manage to find some schematics on the amp , rev I , thats whats on the pcb . that TL072 & TL074 are those op amps ?
Yes TL072 is a dual op amp and TL074 a quad.
Excellent op amps.
 


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