Hum in 5E3

[FREYES_7]

Hello All,

I built a 5F1 from scratch and it sounds fine hehe

Now I tried a 5E3 from a mojo kit and it is hummy,

Any recommendations to decrease the hum?

[tubeswell]

Improve the grounding


https://valvewizard.co.uk/Grounding.html

[FREYES_7]

Improve the grounding


https://valvewizard.co.uk/Grounding.html

Thanks for the wisdom, merlin is the goat

[JPK]

Can you post some pics? Post layout. I built one of these. Totally silent. Boothill kit.

[tubeswell]

Improve the grounding


https://valvewizard.co.uk/Grounding.html

Thanks for the wisdom, merlin is the goat

If it’s already said well by someone, why bother regurgitating it ad nauseum in forums every time someone raises a problem about it? Simpler just to reference the existing excellent work with a handy link.

[dogburn]

Where are your two 100 ohm resistors for the heater wires? They should be coming off of the pilot light and going to ground.

[dogburn]

It's hard to see without close up pics of the chassis & board, but at least from the video, it looked like the resistors (i.e., the artificial center tap for the heater wires) were missing - that could be a big source of your hum.

[FREYES_7]

Indeed thank you very much!

I fixed the earth connections a little bit like in rob robinette's page,

All the pre to normal lo jack's earth

All the power to the same earth connections as well,

The only difference is as I soldered the pots lug to its back, I did not dare to unsolder them, so I don't ruin the pot.  When they are at max the start to hiss so I guess I'll get new pots and solder their lugs to the same pre earth bar, as rob suggests

For home volume levels, the amp noise floor reduced dramatically hehe

I'll mod this kit until it falls apart 

Improve the grounding


https://valvewizard.co.uk/Grounding.html

Thanks for the wisdom, merlin is the goat

If it’s already said well by someone, why bother regurgitating it ad nauseum in forums every time someone raises a problem about it? Simpler just to reference the existing excellent work with a handy link.

[FREYES_7]

Thanks! The PT has 6.3 center tap

Where are your two 100 ohm resistors for the heater wires? They should be coming off of the pilot light and going to ground.

[FREYES_7]

Got so much hate by doing this last time 

Please if anyone has anything to say about my soldering skills, feel free to do so in any form, just let me also know how to improve, this is my second build ever and started learning how to solder just to build amps,

I do have solid theorical knowledge about electricity, so don't fear for my dear life neither, don't know much about amps, but I do know where not to put my hands and to discharge caps

https://imgur.com/gallery/IO1pnLW

Can you post some pics? Post layout. I built one of these. Totally silent. Boothill kit.

[tubeswell]

The vids you posted aren’t hi-res enough to inspect the soldering on-line.


A ‘2-point ground’ usually works well enough for a simple amp like a 5E3, but it also depends on the type of steel the chassis is made of and how good your chassis ground connections are (as well as all the other stuff like your soldering skills ;-) ). The galactic ground scheme in Merlin’s article is a great scheme because it side-steps the variable of poorly founded bit of sheet steel. Not saying the chassis you have used isn’t up to the task - but also not assuming that it is.


But obviously there is some ground hum from what you posted. I’d say there is also hum from one or more other sources. But you could try reducing the ground hum first, and the troubleshoot the other stuff through a process of elimination.

[mresistor]

Hi. If you think it's 60hz hum sometimes a tube can cause hum.