New Champ Build Problems...

[Meaux]

My first Amp build...

Triode Champ Amp Kit... 15watt Upgrade Transformer to run 6L6's... Separate On-Off switch... 470ohm 10 watt power resistor instead of the 5 watt...

I have a Humm problem... Volume control works, dosen't effect the Humm... I get Guitar sound from both inputs... Fuse dosen't blow, no smoke...Checked all grounds till I'm blue in the face... I've re-soldered most of them... Star grounding on Power Transformer Bolt...

I do notice some weird problems... When I turn it off, the Dangerous Filter caps drain themselves... Pretty Safe Amp, but I don't think it should do that...

Voltage Checks yield weird High readings... From L to R on the Weber Layout, I get B+ at 400vdc, not 340... next I get 400, not 275... next I get 352, not 250... then I get 30, not 18... and 252, not 150... and 250, not150...finally I get one right, 1.5 is i.5...

I'm about ready to give up...

Thanks,

Meaux

[Jazz P Bass]

Let's try to narrow this down a bit.
Does the amp hum without an input, all controls off?
Pulling the phase inverter tube should kill the hum, if it is a preamp problem.
If it does not, then that points to the power tube section.

[Meaux]

Let's try to narrow this down a bit.
Does the amp hum without an input, all controls off?

Yep... Hum is there with the 12AX7, and without...

Pulling the phase inverter tube should kill the hum, if it is a preamp problem.
If it does not, then that points to the power tube section.

No Humm with 5Y3 pulled...

No Humm with both 5Y3 and 12AX7 pulled...

[Prattacaster]

It looks like the problem is in the Power section, I'd check the resistance from the positive side of each filter cap to ground. Should be pretty high resistance.

[Meaux]

It looks like the problem is in the Power section, I'd check the resistance from the positive side of each filter cap to ground. Should be pretty high resistance.

Thanks, I'll check that in the AM... I don't do this stuff 'under the influence'... RollTide!!!

[Meaux]

It looks like the problem is in the Power section, I'd check the resistance from the positive side of each filter cap to ground. Should be pretty high resistance.

Yep, as it should be...

[JHow]

I'm not clear which circuit we are discussing. Is this an AA764 champ circuit? To Jazz P Bass' comment does it even have a phase inverter? Is it just a 5y3 - 12ax7 and 6v6 (or 6L6)?

[jmaf]

Severely unmatched power tubes will make it hum without any 12ax7's plugged in.

[MikeH]

Are you using a center tapped filament supply, or the 2 100 ohm resistor method?

[Meaux]

I'm not clear which circuit we are discussing. Is this an AA764 champ circuit? To Jazz P Bass' comment does it even have a phase inverter? Is it just a 5y3 - 12ax7 and 6v6 (or 6L6)?

It's a 5F1 Circuit... http://site.triodestore.com/5F140-18027120V.pdf


The only changes are: 15watt Upgrade Transformer to run a 6L6... Separate On-Off switch (to reduce Humm)... 470ohm 10 watt power resistor instead of the 5 watt that came with the Kit...

[Meaux]

Are you using a center tapped filament supply, or the 2 100 ohm resistor method?

I'm using the the GRN/YEL - RED/YEL to Power Trans. as pictued in this Layout... http://site.triodestore.com/5F140-18027120V.pdf

I 'alligator clipped' the 2 100 ohm resistors in with no effect... I also tried a GZ34 Rectifier Tube with no effect either... I have swapped out numerous 12AX7's, and 6L6's, all with the same Humm...

[Prairie Dawg]

Well, you're down to a few possibilities-either there's a bad component or you've got something miswired. The latter should be easy enough to check.

[Jazz P Bass]

I'm not clear which circuit we are discussing. Is this an AA764 champ circuit? To Jazz P Bass' comment does it even have a phase inverter? Is it just a 5y3 - 12ax7 and 6v6 (or 6L6)?

Duh!
Single ended Champ.
No, there is not a phase inverter.
Thanks
(brain fart)
Still, if pulling the 12AX7 does not get rid of the hum, the problem lies in the power section.

[Meaux]

Duh!
Single ended Champ.
No, there is not a phase inverter.
Thanks
(brain fart)
Still, if pulling the 12AX7 does not get rid of the hum, the problem lies in the power section.

So, should I just order the entire list of components X 2 and start with replacing the filter caps and the 2 resistors first? Since I'm gonna have to start yanking parts, I like everything I've read about a choke replacing the 10K resistor, makes me want to go that route... I just don't know which choke to buy...

[JHow]

So, should I just order the entire list of components X 2 and start with replacing the filter caps and the 2 resistors first? ...

If your parts are new, I wouldn't order more parts. Most likely scenario is something mis-wired. For me personally, trouble areas are: input jacks, OT to output jack, grounding. You may need to play with the latter. Also, I typically favor shielded wire on the grid inputs to the 12ax7.