Unsolved problem EL34/12AT7/5AR4

Delphaure · 4th October 2008, 03:26 PM

Hi guys,

(I'm a real newbie, so please be indulgent with me

)

Someone gave me a SE EL34/12A*7/5AR4 amp.
It sounds quite good but one channel is louder than the other, particularly in the mid-range.

I swapped tubes, swapped and changed the 12A*7; the only one I didn't change is the rectifier.

I interchanged my speakers; I tried the amp with another pair of speakers. I swapped wires and changed them.

I checked soldering, resistors and caps. Everything seems OK. But obviously, there is something wrong. Because one channel is always louder than the other.

The next step I should do is checking transfos. Gosh. I'm not really sure what to do about that...

Before this step, do you think I could do something else, that is obvious for an old DIY pro but unevident for a rookie ?

I know I should have done the schematic, but I didn't

Thanks a lot

TubeHead Johnny · 4th October 2008, 07:55 PM

How old is the amp? Sounds to me like a resistor or cap has drifted in value, making the channels sound uneven.

Do you have knowledge working with high voltage electronics? If not get a qualified tech to check it out. Voltages inside an amp are deadly!

4th October 2008, 03:26 PM	#1
Delphaure diyAudio Member Join Date: Oct 2007	Unsolved problem EL34/12AT7/5AR4 Hi guys, (I'm a real newbie, so please be indulgent with me ) Someone gave me a SE EL34/12A7/5AR4 amp. It sounds quite good but one channel is louder than the other, particularly in the mid-range. I swapped tubes, swapped and changed the 12A7; the only one I didn't change is the rectifier. I interchanged my speakers; I tried the amp with another pair of speakers. I swapped wires and changed them. I checked soldering, resistors and caps. Everything seems OK. But obviously, there is something wrong. Because one channel is always louder than the other. The next step I should do is checking transfos. Gosh. I'm not really sure what to do about that... Before this step, do you think I could do something else, that is obvious for an old DIY pro but unevident for a rookie ? I know I should have done the schematic, but I didn't Thanks a lot

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4th October 2008, 07:55 PM	#2
TubeHead Johnny diyAudio Member Join Date: Jan 2005 Location: The emerald city, Seattle, WA.	How old is the amp? Sounds to me like a resistor or cap has drifted in value, making the channels sound uneven. Do you have knowledge working with high voltage electronics? If not get a qualified tech to check it out. Voltages inside an amp are deadly!