Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on May 08, 2017, 05:58:24 pm

Title: Bad tube or bad cap?
Post by: Colas LeGrippa on May 08, 2017, 05:58:24 pm

Hi my friends, got an amp here that works fine but from time to time gives a loud fart ( just like me  :icon_biggrin: ).  Are there more chances that the sound comes from a bad tube or a bad cap? The chopstick method did not reveal nothing.


Thanks


Colas

Title: Re: Bad tube or bad cap?
Post by: shooter on May 08, 2017, 07:10:47 pm

Quote

bad tube or a bad cap

try monitoring voltage over time, maybe hours, at idle.  dropping Volts "should" indicate a leaky cap. swap tubes and see if it farts

Title: Re: Bad tube or bad cap?
Post by: Colas LeGrippa on May 09, 2017, 04:29:26 pm

Q: bad caps or bad tubes?
A: Bad tubes.


I was surprised to realize that old tubes could fart from time to time and still sound good. I put the beast on test for 12 hours while working and swapped the tubes for new ones. That was the easiest move to make before replacing the power caps. I didn't have to change the caps, farting has stopped with new tubes. The old tubes were drawing approx. the same current as the new ones. What happened in them? Stomach problem ? :laugh:


Colas LeGrippa

Title: Re: Bad tube or bad cap?
Post by: shooter on May 09, 2017, 06:31:19 pm

Quote

I was surprised to realize that old tubes

I talked with a musician after his set, told him I thought his tubes were about dead, he smiled, said he knew, then told me there is no sound better than a twin with dying tubes.  I did agree he had a great set, although the tech in me was twitchin :icon_biggrin:

Title: Re: Bad tube or bad cap?
Post by: Tony Bones on May 09, 2017, 06:34:20 pm

It might have been dirty contacts somewhere, probably on the tube sockets . Pulling out the old tubes and pushing in the new ones cleaned the contacts enough to stop the unpleasant noises.

Just for kicks, try putting the old tubes back in.

Title: Re: Bad tube or bad cap?
Post by: Colas LeGrippa on May 11, 2017, 08:23:35 am

Just for kicks, tubes were bad.


Have a good day!


Colas

Title: Re: Bad tube or bad cap?
Post by: Tony Bones on May 11, 2017, 08:00:22 pm

Sorry. Didn't mean to offend.  :)

Title: Re: Bad tube or bad cap?
Post by: John on May 11, 2017, 08:27:14 pm

You can't offend Colas, he's too busy kissing his wife.  :icon_biggrin:

Title: Re: Bad tube or bad cap?
Post by: Willabe on May 11, 2017, 10:14:08 pm

Quote from: John on May 11, 2017, 08:27:14 pm

You can't offend Colas, he's too busy kissing his wife.  :icon_biggrin:

  :laugh:

Title: Re: Bad tube or bad cap?
Post by: Colas LeGrippa on May 12, 2017, 04:24:18 pm

how did you know about my wife ???? :w2:

Title: Re: Bad tube or bad cap?
Post by: Colas LeGrippa on May 12, 2017, 04:26:49 pm

she told tou you everything about me, didn't she ? :laugh:

Title: Re: Bad tube or bad cap?
Post by: Colas LeGrippa on May 12, 2017, 04:27:48 pm

oops sorry for the ''tou'' ( it is not even a french word....)

Title: Re: Bad tube or bad cap?
Post by: PRR on May 12, 2017, 11:01:05 pm

> how did you know about my wife ????

She tells us every night.  :grin:

> oops sorry for the ''tou''

Just FYI: there is a "Modify" icon (http://el34world.com/Forum/Themes/default/images/icons/modify_inline.gif) above and/or below your posts. You can fix your own words before anybody sees them, or even later.

Do be careful. Some browsers jump to the bottom of the page "New message" instead of the Modify Message box.

Title: Re: Bad tube or bad cap?
Post by: Colas LeGrippa on May 13, 2017, 10:08:38 am

OMG, my wife won't get any kiss from me for a while....