Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bibio on November 05, 2019, 08:01:45 am
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Hello,
I recently finished building a 5F1 style kit amp for a friend. I upgraded some of the components but all values were kept the same.
It sounded great and worked perfectly.
After a few weeks, it started to develop this noise after around 15mins of use:
https://vocaroo.com/i/s1HtgRzWCPc6
As you can hear from the link there is a lot of hum and a popping sound.
Unfortunately, I'll be away for the next month so won't be able to inspect it.
The sound is quite unique, does this ring a bell with anyone?
Strange it only happens after 10-15 of use, sort of implies its heat-related????
When it was built it had all brand new components fitted. Cathode, screen and plate currents all verified and dissipation checked.
I'm quite confident it's not a dry joint or lose connection but open to all possibilities.
Could anyone hazard a guess at a potential cause of the issue?
All help much appreciated.
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Might be bad tube or RF interference.
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Strange it only happens after 10-15 of use, sort of implies its heat-related????
I'm quite confident it's not a dry joint or lose connection but open to all possibilities.
Could anyone hazard a guess at a potential cause of the issue?
All help much appreciated.
Yes, heat is a good guess.
Tube could be bad, but doesn't revel itself until after getting hot, grid/cathode/heater alignment could move with heat.
I know you think your solder connections are good but, could be bad solder joint, common for this to revel itself after heating up. Hum and popping are common symptoms.
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Hi Guys,
Thanks for the response.
It's a difficult one to identify with the limited information.
Equally frustrating I can't start fault finding right now!
You know that feeling when you can't wait to solve a problem.......
Not exactly sleepless nights but lots of wondering, did I make a mistake????
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sounds like arcing. is the 5Y3 healthy? cold solder joint?
--pete