I want my fender champ II to break up sooner

[jdl]

Hey;

I have 1982-83, Fender Champ II amp. I was wondering if their are some tubes i can put in it to make it distort at lower volume settings. Money isnt really an issue, because as far as I can see tubes are fairly cheap. Is it possible to do this? and if so is it going to be a fairly noticeable difference?

James

[jdl]

Also, what does the "hum balance" thing on the back of my amp do? it looks like you put a flat head screw driver in it and twist?

James

[UnklMickey]

James,

i thought i had an answer for your first post. then i saw your second post.


the champ was a fairly simple amp with 3 tubes. 12ax7 preamp, 6v6 output, 5y3 rectifier.

but it didn't have a hum balance pot.


do you have a schematic, a chassis number, or can you tell me how many and what type the tubes are?


a hum balance pot is usually wired with each end connected across the filament winding and the wiper connected to ground.

with no input, and the volume turned up, adjust it for minimum hum.

you can't hurt anything if it's misadjusted. you'll just hear more hum.



unk

[jdl]

thanks unk;
Here's the info. This is what the sticker on the inside says: 2x 6V6, 2x 7025. Serial number: F305807. Also, the guy that i bought it from said that his amp tech checked it out, and as far as he knows the tubes were all original.

James

[UnklMickey]

i found what i think is the schematic for your amp here:


www.geocities.com/twoseriesfenders/champiischematicwiringpartslist.pdf


unfortunately changing the rectifier tube to one that would have more loss isn't possible, 'cause it doesn't use one.

if you have the export model, you could change the taps on the primary of the power transformer. by using the 240v and 100v connections, with a 117v input that would be like running on a variac at 98volts. sort of an eddie type thing. tends to eat tubes a bit faster (the cathodes degrade more rapidly when the filaments are colder), but gets you that "brown" sound.

or you could just buy a variac.


another possiblitiy would be to add a big power resistor or zener diode in series with the B+ from the solid-state rectifier and the first filter cap.

as far as tube changes, you might be able to find another type of output tube that uses the same pinout and will idle at higher current than a 6v6. might be a bit risky though, could cause your output transformer to fry.


if you're not experienced in modding tube amps, and don't mind replacing tubes more often, the variac idea is probably the easiest.


unk

[jdl]

Hmm...
Thanks unk, i understood a bit of what you said lol! But I think i should do some reading so i can fully understand what you meant. If you have time could you "dumb down" your post for me! If not Ill just read up and hopefully make sense of it.

Thanks for your time;
James
P.S. What is a variac?

[UnklMickey]

a variac is an adjustable transformer.

plugs into the wall, your amp plugs into the variac.


should cost $100~200. you'll need one with at least the current rating of your amplifiers requirement (1.5 ampere).

higher current capability means that you would also be able to use it with a bigger amp.


get one with a built in meter so you can see what voltage you are adjusting to. and DON'T run it above 120v output.


read more about it here.


www.amptone.com/tenmavariac.htm


if i have to dumb-down the info on mods, you probably need to learn more before you would want to attempt them. making mistakes inside tube amps can cause damage and more importantly it can KILL you. (about 400 volts)


good luck with the variac Eddie. i mean James.



unk

[jdl]

lol thanks unk;

no i would never try any thing with that much 'lectricity pumpin through it without doing alot of reading up.

thanks for the info;
james