Burning smell coming from my BFDR

AlRob

Member
Messages
174
Last night I was rehearsing with my 66 BFDR and after about an hour i began to smell a strong burning smell. I immediately shut it down and unplugged it. I sniffed around and it seemed to be coming from the transformer side of the chassis. Could this be the transformer burning out? The only thing I've done lately to the amp was to install a NOS RCA 12AX7 tube in the V2 slot just last week.
If this is the transformer does anyone have a suggestion for a replacement?
Thanks appreciate the help.
 

Blue Strat

Member
Messages
30,744
First things first. Check the bias on the power tubes and measure the 470ohm screen grid resistors for the power tubes.

If you don't know how to do this find someone who does.

Has the amp ever had a cap job? If not, that could be what caused the problem (the bias cap in particular). If it hasn't you need to do that before anything.
 

guitarcapo

Senior Member
Messages
2,326
It's probably not the transformer. More likely a burnt out cap or resistor along the rail or plates of the tubes where the high voltage is. I'd at least check there first. "All original components" on a 46 year old amp is not a good thing..... contrary to what collectors might tell you.
 

AlRob

Member
Messages
174
First things first. Check the bias on the power tubes and measure the 470ohm screen grid resistors for the power tubes.

If you don't know how to do this find someone who does.

Has the amp ever had a cap job? If not, that could be what caused the problem (the bias cap in particular). If it hasn't you need to do that before anything.

Thank you, I don't believe its ever had a cap job.
I forgot to mention in the original post that the amp was sounding fine at the time I smelled the burning.
 

AlRob

Member
Messages
174
It's probably not the transformer. More likely a burnt out cap or resistor along the rail or plates of the tubes where the high voltage is. I'd at least check there first. "All original components" on a 46 year old amp is not a good thing..... contrary to what collectors might tell you.

Thank you thats good news. I think the amp over due for a check-up
 

Blue Strat

Member
Messages
30,744
Thank you, I don't believe its ever had a cap job.
I forgot to mention in the original post that the amp was sounding fine at the time I smelled the burning.

There's a saying in the amp tech world. "The best sounding amps are the ones just about to melt down".
 



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