Slight Hum vanishes when volume or tone cranked .

[showbander]

this one

[cbass]

Looks right.
i would try taking that 100 ohm out and conecting the CT directly to pin 8
Martin probably has a better idea than me so wait for him.

[showbander]

ok will try that...thankyou indeedy

[martin manning]

Cbass, I don't know why that 100R won't be fine there between heater CT and Rk, but maybe it will make some difference.

Showbander, can you post a pic of the input jack and first cathode grounds?

[ToneMerc]

Cbass, I don't know why that 100R won't be fine there between heater CT and Rk, but maybe it will make some difference.

Showbander, can you post a pic of the input jack and first cathode grounds?

Martin, I built a couple the Weber 5F2H ciruits, which float the filament CT 100 ohms above the cathode , it seemed to work ok.

TM

[showbander]

cheers guys, i removed the 100ohm resistor and no change.

Is it possible noise at inputs....if i hook a small patchlead to inputs(no guitar connected) with the 1 meg resistor on i get alot of noise when volume turned up.

Doing the same in the other inputs much less noise ,very noticeable !!!

I know my soldering is slightly dodgy at inputs so i shall redo that.

[showbander]

i will get pics up tomo as they make more sense than words....usually

[showbander]

right guys i have sourced the hum ...it seems the closer the large 25 watt resistor is positioned to the first 40uf cap the more hum increases....i have moved as far away as possible with what length of the resistors legs allow me....any fix for that such as lengthening legs and positioning away from cap , would this be ok ?
Thankkyou

[martin manning]

The 25W resistor is carrying the B+ to the OT center tap, and has a high ripple current. It's 120 Hz. In the Weber layout the power tube grid wires pass near that resistor, and I'm inclined to believe that is the issue rather than the proximity of the resistor and the 40uF cap. Can you separate the grid leads from the leads connecting the resistor to the standby switch? Note in the Weber layout the red lead from the OT is routed well away from the power tube grid leads.

[showbander]

cheers martin. do you mean these 2 (arrowed)
Thanks

[showbander]

yeh at moment the red OT lead is tied in with other ot leads & directly over 6v6 socket wiring ...i will change this later. I hope we may have it cracked coz it,s def better after tilting the resistor back and also pushing the 4n7 tone cap higher as you show in your grounding scheme.

[martin manning]

cheers martin. do you mean these 2 (arrowed)
Thanks

I was referring to the red wire arcing over from the lower end of the 25W resistor to the OT. Keep that and all of the HT leads away from grid wires and tone stack wires and caps.

[showbander]

Hey martin...You /we have cracked it. You were right with your suggestions.
I moved the red lead from near the 6v6 and the big resistor ,moved the tone cap above the pot an the hum has all but gone and followe your grounding scheme.

Thanks very much for all your help & anyone else that chirped in , much appreciated. Time to Enjoy it fully now !

I have learnt lots here if i ever do a build again.
A fantastic Forum this is !

[martin manning]

Cheers, good to hear it's sorted out, and we're all a little smarter now ;^)