Fender Champion 600 Mods

matta

Hey Guys,

Well since there are a couple of you interested in the geeky side of things I thought I'd post some info on a amp mod/rebuild I just did for a fellow Forum member.

As you may know Aja already owns a Champion 600 that I modded, which he affectionately calls the 'matta edition', LOL. Well this amp was no different, it contains the same mods PLUS 2 new additions. I replaced the stock chinese output transformer with a USA built one and I also added a three way switch to change the output from Pentode (5W) to Triode (2W) with a 'Center Off' position which puts the amp in Standby.

Here is the stock amp, both the innards and the cabinet/chassis.

The weird thing about the Champion 600 is is that is NOT a Champion 600 circuit, it is actually a BLACKFACE CHAMP with a fixed tonestack, voiced to work with the stock Chinese Speaker, giving it an almost 'HiFi' tone, not very rock and roll... that changed...

So here is a shot of the innards once I'd completed the mods:

In order of events we have the following:

1. DC Heater Mod: Basically the stock amp is buzzed like crazy at higher gains, so in order to tame the beast so to speak(er) I converted the AC Heater/Filament to DC using a Bridge Rectifier and a hefty 4700uF cap.

2. HT Drop and Increase Filter Caps: The stock Chinese Power Transformer puts out WAY too much juice, a little drop was in order and at the same time the extra filter caps take away the VERY annoying hum that this amp produces stock.

3. Replace and Reposition Output Transformer: Firstly the stock OT is WAY too close to the Power Transformer, again adding to the annoying hum that the amp produces stock, by repositioning it you clean up the hum... I went one step further and decided to replace this with a US MADE OT... one Caveat... it seems the Chinese have their colour coding backwards as the first time I turned the amp on she squealed like a banshee... turns out the secondaries are reversed on the Chinese clone...

4. Revoice to Tweed 5F1 Specs: As shared above the amp is actually based on the BLACKFACE CHAMP (AA764), with a fixed tone stack voice for the chinese speaker... not very rock & roll like. I swapped out the 6" chinese speaker for a 6" Jensen Mod, ideally an 8" would be better, but the baffle cannot accommodate it and 6" is in keeping with the original Champion 600. I then changed the circuit to follow the 'classic' tweed era 5F1 circuit, this opens the amp up and gives it alot more gain/grunt.

5. 6V6 Circuit Mods: A couple parts changes here will make the Output Tube last alot longer....

6. Install HT Fuse: Just as a precaution I added a fuse to the HT line, a cheap fuse is better than loosing a power transformer...

7. Combined Triode, Standby & Pentode Switch: Soldistate rectified amps SHOULD have a standby switch to allow the heaters to warm up before hitting them with HV, which can cause cathode stripping. At the same time I decided to make it a '3 way switch' allowing the output valve to be switched between Pentode and Triode operations, so the amp can be set to 2 Watt or 5 Watt operation, great for cranking the amp without annoying the neigbours ?

And here she is, chassis fitted, ready to play. At the same time the Chinese tubes had to go and she got fitted with new JJ's, you can see the repositioned output trano as well (compare it to the stock amp above).

Ok, so what does she sound like? Well at 5W's she doesn't have much clean headroom and was built for rocking, below are 2 clips, one with the stock 6" and then driving my Jensen equipped Fender 2x12 cabinet, both are Ceramic.

Champion 600 6" Jensen MOD Speaker
Champion 600 12" Jensen C12N Speaker

The amp was played using my PRS SE ONE into input 1, guitar volume maxed, amp volume at 10 (it goes to 12!).

Well I hope you enjoyed amp modding 101... tune in for more adventures soon.

Matt

MikeM

? ?

BRAVO!!!!

racman

Can't wait to get it and start playing - thanks Matt!!!! ?

Vick

Dud,a few questions,what level of understanding/knowlige must one have to perform these mods...?
Are the instructions on the net that r reliabil for the mods?
Were duz one get the components for the mod?
AND
and hows the SE one? ?

matta

Hi Vick,

RE skill level, um, this is NO BEGINNERS project! We are dealing with HV lines in excess of +300VDC, if you screw up it could lead to death as those voltages are lethal... HV scared me for years. I'm a cautious guys and spent 5 years on solid state electronics before attempting my first tube mic pre build a few years ago.... so take that for what it is worth... as a friend of mine has written on his commercial units "Warning - Death is permanent".

RE what is available on the web, there are LOTS of mods, some reliable, others not, other are for sale and generally come with instructions/parts and photo's making the build out alot easier for those that need paint by numbers and don't understand terms like "cut the trace at the junction of C2 and R10, jumper said trace to a middle contact on a SPST switch" etc... if that is all greek... buy a paint by numbers mod kit ?

I can recommend the Alnico Mods (Nigel) for amps like the Harvey Benton/Champion 600/Epi Junior/Blackheart BH5 and ones I incorporate into my own amp mods. Check out his Ebay shop here: http://stores.ebay.com/alnicomagnetp. Bill M's mods are also recommended for Fender Blues Jnr's, http://www.billmaudio.com/ you can also look at the Mercury Magnetics upgrade kits: http://www.mercurymagnetics.com/pages/catalog/kits/index.htm

Again all these projects are potentially lethal and can result in serious injury at best, death at worst... proceed with caution and at your own risk.

RE parts, I stock a fair few bits and have several suppliers that I regularly import from worldwide, contact me if you need anything in particular.

RE the SE ONE, I love it, it is somewhere between my Tele and Les Paul Jnr, sounds great, feels just as good.

Cheers

Matt

Vick wrote: Dud,a few questions,what level of understanding/knowlige must one have to perform these mods...?
Are the instructions on the net that r reliabil for the mods?
Were duz one get the components for the mod?
AND
and hows the SE one? ?

Vick

....Death? ?

oky...think im gona put that on hold...

r there any books you chould recomend for just an "introduction" into these things?

thanx man

matta

Hmmm.... a couple good ones are Forrest Mims "Getting started in Electronics", a nice 'beginners' book. A staple to have on your shelf is Horowitz and Hills 'The Art of Electronics', the digital section is somewhat dated, but good solid basics all round... I'd start with a few basic solid state projects first before tackling any HV stuff.

Cheers

Matt

Wizard

I had 'The art of electronics'.
My electrical engineer friends had it as a text book at university when I was there ... many, many moons ago.
Cool book.

Vick

Thanx man,il c if i can get hold of a copy