Another Champion 600 help thread

[SamuraiJackson]

Hi Guys,

first of all, I'm a total noob of guitar amp electronics and modding, so sorry for this.
I bought an used champion 600 and modded it to almost tweed specs I believe. What I've done is to remove the tone stack,adding the .022 coupling cap from top of r18 to bottom of r20, changed the R10 resistor to 680k 2w, removed C10 and jumpered R3. Also changed R7 to 48k if I recall correct?

Now, when I turn the amp on, I got almost no volume until the knob is at noon, and then, if I hit the strings strong enough the amp farts loudly. Tubes are glowing and fuse looks good. I checked all the solderings and everything looks fine. Do you have any idea of what's going wrong? Did I forget something?
Hope someone can figure it out!





Kind regards,
SJ:

[Enzo]

It pays to know what each part does. R10 is the power tube cathode resistor, and changing it from 470 OHM to 680k OHM is not going to work. 680k is 680,000 ohms. A 680 OHM might work, but not sure why we want to change that.

Removed C10 and R3 and replaced them with a wire????? That leaves the tube with only 47 ohms in the cathode lead, and that also makes R7 kinda pointless.


What old schematic are you trying to emulate? I don;t see a 680k or even a 680 ohm power tube cathode in the fenders I have. Nor those other changes.

[SamuraiJackson]

Hi Enzo,

I believe you found the main problem, which is the R10 resistor changed with the wrong value. It must be 680 not 680k! For what I understand, changing the R10 value help the power tube dissipate less current or something like this? I took all these mods idea from the topic regarding Champion 600 upgrades in the Telecaster discussion page. I'm going to change R10 to 680ohm and report back!

Thanks!

[Enzo]

I was not aware these amps drew too much power tube current in the first place, but i guess it can;t hurt.

I would say that whole C10/R3 thing is either a mistake or at least wrong, it makes no sense, and is not likely to work well.

[SamuraiJackson]

I think that the original tweed champ had only one or not at all cathode bypass cap, that's why the guy that did the mod in the first place took C10/R3 out? And yeah...I have almost no idea of what I'm doing! Thanks again Enzo.

[Enzo]

The original Champ also used a pentode instead of triodes. Removing the bypass cap is one thing, but removing the whole cathode resistor and replacing it with a wire is something else completely.

[SamuraiJackson]

So is it better to put the resistor back in R3?

[SamuraiJackson]

I changed R10 to 680 and It works! Thanks a lot Enzo. I think I'm going to put R3 back and R7 to stock.