Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: newguitarsmell on January 10, 2019, 07:11:03 pm

Title: Hoffman 5e3 build - no hum/hum
Post by: newguitarsmell on January 10, 2019, 07:11:03 pm

Hi
I built a Hoffman 5e3 - spent a long time retiring things last night and the amp sounded great. It continued to sound great until after about an hour I started hearing noise. It was a combination of radio noise which progressed to a pretty loud hum.
I don't know how or where to take voltages - so if somebody could let me know what to post to get help.

I will recheck all the solder joints - I am so close!
Thoughts?

No filament wires are touching each other.

Title: Re: Hoffman 5e3 build - no hum/hum
Post by: vampwizzard on January 10, 2019, 07:28:08 pm

Id go back through it and check for cold joints and places where you may inadvertently have grounded it.

also, https://el34world.com/Forum/index.php?topic=17701.0 (https://el34world.com/Forum/index.php?topic=17701.0)

Title: Re: Hoffman 5e3 build - no hum/hum
Post by: PRR on January 11, 2019, 03:17:53 pm

Crap that builds over an hour has to be a poor mechanical "joint". Expands, loses contact.

Which in a guitar amp, is most likely a "soldered" joint that isn't really metal-to-metal "wet", but just globbed-up on top of tarnish. (It could be a loose ground bolt or a highly tarnished chassis at that bolt.)

Title: Re: Hoffman 5e3 build - no hum/hum
Post by: VMS on January 12, 2019, 12:41:10 am

If you're using new set of tubes i would try to swap the tubes to older set that you know works

Title: Re: Hoffman 5e3 build - no hum/hum
Post by: newguitarsmell on January 14, 2019, 12:14:30 am

I am going to resolder. Had a bit of a time getting the solder to stick to the back of pots, even with flux but it worked. Will check back. Might also bias the tubes.
Tubes are NOS. Amp sounds great, but starts to hum. I suspected it was a solder/heat thing.
Thanks all!