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FDP Forum / Amp Mods, Repairs, and Projects / voltage on blue jr filter cap


Kansas City

It's in Missouri
May 9th, 2017 04:39 PM   Edit   Profile  

I just installed the Bill M tone stack mod on my blues jr. the amp sounds really good but measuring the voltage on the new filter cap reads 740v and I thought it was only supposed to be about 330v.I am attaching the negative to the chassis and the positive to the positive side of the filter cap. My meter only goes to 500v.Why am I getting 740v reading? I am not a pro just wanted to give it a try. Like I said the amp sounds good but just concerned about that voltage. Also I got a reading of about 260 degrees when I put a digital thermometer probe on the outside glass of the power tube. Is that to hot?


Cincinnati, USA

May 10th, 2017 08:34 AM   Edit   Profile  

AC or DC?


Kansas City

It's in Missouri
May 10th, 2017 09:55 AM   Edit   Profile  

Had meter set for AC


Kansas City

It's in Missouri
May 10th, 2017 10:31 AM   Edit   Profile  

Set the volt meter for DC and got 335v. I'm guessing that's what I should have been doing in the first place? If so appreciate the info amphead4, thanks.


Cincinnati, USA

May 10th, 2017 10:41 AM   Edit   Profile  

Common mistake!



May 11th, 2017 12:12 PM   Edit   Profile  

After rectification the voltage is DC. Just not filtered.

FDP Forum / Amp Mods, Repairs, and Projects / voltage on blue jr filter cap

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