5e3 Build noise with volume passed 4

[rud85ny]

Finished building 5e3 Tweed Delux, all of my pin out voltages are within spec, the transformers and tube temperatures are within spec. The preamp and power supply are grounded in separate posts that are ultimately chassis grounded. For the life of me i can not remove this humming/ poping noise. Anything over 3-4 volume on any channel produces tremendous hum. I posted a vid on youtube. please help!!!

https://www.youtube.com/watch?v=2Qy5czgat7o

[Planobilly]

I will try to help but I need a couple of things.

Post the schematic you used.
A photo of the inside of the chassis. We need to see the wiring as clearly as possible.
Disconnect you guitar and report the hum as you turn up the gain.

If you have a scope or a DMM that can measure the frequency of the hum at the output transformer do that. As it is a low pitch hum it could be 120Hz.
If you have a scope measure the ripple at the the filter caps.

Things to check for...heater wiring...connection to ground for the filter caps.

Cheers,

Billy

BTW...if you do those things there are several people here that can help

Cheers,

Billy

[eleventeen]

Quick thoughts:


Your volume control, to me, is dangerously close to the power transformer. Without seeing the guts, I would suspect using shielded wire with that mechnical/physical layout would be mandatory.


Cut all power & drain all caps. Clip 1 lead of your ohmmeter on one end of every pot and clip the other lead on the center/wiper terminal of every pot. Have to use clips because you need a hand or two free. Now rotate the pot very slowly and be sure you have contact (meaning SOME reading) all the way around as you turn. Move the end connection to the other terminal of each pot and do the same. The suspicion that you may have a funny pot is aroused because of how your tone control cuts in the hum all of a sudden. Not that likely but possible.


I think you're going to have to run shielded wires everywhere up through the first triode. There are lots of 5E3 guys here and you should get some good tips. Me = less.

[rud85ny]

Thanks for the reply guys, i shall take those steps. And try to get good photos. As far as shielding or interference noise, wouldn't it be apparent and consistent at all volumes? and also the super loud poping and High pitched hiss consistent with  the photometer positions seems like its some sort of out of limit value that gets exaggerated at certain Pot Resistance values. Notice how at around 2 o'clock everything works but past that it goes over bored. 

[shooter]

wouldn't it be apparent and consistent at all volumes

you need a certain level before a signal will "feedback", or "crosstalk".

spend some quality time looking, wigglin, and swapping, you should be able to isolate the problem to a single stage pretty quick.

[sluckey]

These type of problems with a new build are almost always due to a wiring error, poor layout or workmanship, or wrong component value. Compare your schematic, layout drawing, and actual build. They should all agree. Sharing your schematic and layout and some hi rez pics may help us spot something. Follow the link in my signature line at the bottom of this message for some good techniques on verifying your wiring.