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Post subject: Makin' that Champion 600 a Champ! easy mod, no parts
Posted: Thu May 27, 2010 9:30 am
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I finally got myself together to do some proper troubleshooting on my broken champ 600. The 470ohm 2w resistor at the cathode of the 6v6 was completely shorted. But that's not what this is about.

After doing a bit of reading and checking schematics I decided on the prob easiest mod to do to this little beast.
Just 'cause theres only a volume knob doesn't mean this thing ain't got a tone stack. BUT, the tone stack is a fixed resistor Blackface type, and the champ sound as we know it from Layla is definitely tweedish!
So what to do? REMOVE IT! Simply lift up R19, you don't have to take out the circuit board to solder on the back of it, just heat up one leg of the resistor, add some solder and pull it up with a plier, just one leg, and that's it, the tonestack is bypassed to get rid of that shrill mini-blackface sound(blackface sound is fine, it just has to be HUGE and with a speaker that doesn't break up)
But while we're at it, lets give R7 the same treatment, this should remove NFB(negative feed-back) from the circuit, making the amp WAY more gainy.

And that's it, no new speakers, trafos, caps or resistors, just half an inch of solder, and 10 mins work including disassembly and re-assembly

Turn the amp to 5, this'll be WAY WAY louder than 12 before the mod, and you'll agree that LAOALS could very possibly be recorded with champs

I don't get it, Fender really $@!&*% this one up, big #$@*&!% time! :roll:

I'm laughing my $@! off in sheer joy of the wonderful sounds this baby produces now
try it, you won't be disappointed and by lifting the resistors u can easily solder them back in to re-ruin your champ :wink:
An alternative would be to change the tone stack resistors with trimpots of similar resistances, dial in your tone and leave it, cutting holes in the front to mount up external pots for a 'normal-style tone control' is too much hard work for something unnecessary

Ain't got speakers or tubes to replace but i'll try to fit some grill cloth from and old radio instead of the woolly velvet curtain Fender used


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Posted: Thu May 27, 2010 12:01 pm
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That sounds pretty cool, Time-Machine. I've been considering picking up one of those little amps, and this might be worth trying. Could you possibly upload some photos? 8)

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Posted: Thu May 27, 2010 3:20 pm
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russianracehorse wrote:
That sounds pretty cool, Time-Machine. I've been considering picking up one of those little amps, and this might be worth trying. Could you possibly upload some photos? 8)


Not much to see, just pulled up a leg on each of the above mentioned resistors. Ain't got cash for tubes, speaker or transformers the next couple of weeks
I didn't get to change grill cloth as I've just spent the entire evening rewiring my epiphone, *sigh*, after today, i might very possibly start refusing to work on chinese productions for the future

I'm busy all day tomorrow, but if you really want to see the guts of this thing I'll get some pics during the weekend. It's not pretty though :lol:

I'm starting to think this thing might be worth a cap job and replacement of the critical links, even carbon comp resistors, though the circuit board and layout of the wiring is kinda messy
But the amp is just freakin' charming!
The speaker is not as bad as people say, but it cannot handle the amps output when mod'ed, so a replacement will sure be nice


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Posted: Thu May 27, 2010 3:46 pm
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Oh, one important note, my amp came with an EHX 6v6 out of the box, the 12ax7 is a no-name made-in-china (if i'm really lucky I'll trade myself a mullard tomorrow, from a classmates Hagström restoration)


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Posted: Thu May 27, 2010 7:51 pm
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That sounds pretty interesting. Might give it a go.
On the subject of valves, I replaced the stock (no name) 6v6 in mine for a JJ and noticed a HUGE improvement in the sound. I then swapped the 12ax7 for an EHX but noticed no change, other than the slightly fatter tube was very difficult to get into the holder.

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Posted: Sun Jun 20, 2010 2:10 am
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Stupid question time.

So, you pull this resister off one side to brighten it, ok, but how hard would it be to add a tone pot to get some control?

Seem like all you would need to do is drill a hole for the pot, install say a 250K, take a lead off the board and replace the resister running it through the pot.

Might be a fun Idea, yes?


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Post subject: Re: Makin' that Champion 600 a Champ! easy mod, no parts
Posted: Wed Jan 15, 2014 4:42 am
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Did you try to replace the resistor with a pot of similar value?
Did it work and sound nice?
I am thinking about modding my Gretsch 5222 this way at R7 and R19.
So i would have one Gain and one Tone Control Pot :)


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Post subject: Re: Makin' that Champion 600 a Champ! easy mod, no parts
Posted: Wed Jan 15, 2014 8:55 am
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Actually, it looks like the tone-stack is still in place, even after removing R19. Removing R19 maybe like cranking all the tone controls to "10." You'd need to replace the tone-stack with a 0.022mfd coupling cap to truly revert the amp to 5F1 standards. I've done this with several BF and SF era Champs and VC's. Works out nicely.

And if you need a bit of GNFB... replace R7 with a 22k-ohm resistor = 5F1.

Anyhow, it's being a bit anal. If the mods works, as you stated, go with it. Easy mod and it's easy to re-configure back to stock.

Thanks, for a nice tip! :D :mrgreen: :D


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Post subject: Re: Makin' that Champion 600 a Champ! easy mod, no parts
Posted: Wed Jan 15, 2014 1:39 pm
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Do it the right way:

viewtopic.php?f=13&t=63259

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