#2
Well I've done basically the same thing to my vavle junior. Do you have an understanding of how an amp works or how to read a schematic?
Guitars:
LTD F-50
Yamaha EG-112
'77 Harmony
Roadworn Starcaster
Gretsch G5120

Amps:
Vypyr 15
Epiphone Valve Junior combo
#3
so so, but my brother is electronic engineer and he told me to find a diagram or something like that cus he know how he COULD do it but dont want to f*ck up the amp if something goes wrong, thats why I'm asking for someone who has already done it
#5
Well all I'm finding is the schematics of the old versions, ask him if he knows how to discharge caps and ask him if he's ever worked with tubes.

Also are you wanting to have the master volume too? Because on small amps like this they're not very effective and the pre-amp overdrive you get is like almost none unless you use a guitar with really hot pups. And are you wanting treble mid and bass? Because the older ones just had Treble and Bass.
Guitars:
LTD F-50
Yamaha EG-112
'77 Harmony
Roadworn Starcaster
Gretsch G5120

Amps:
Vypyr 15
Epiphone Valve Junior combo
Last edited by grungebaby at Aug 5, 2011,
#6
I added a mid control on my Champ 600, since boosting the mids acts as a gain boost when you push the amp all the way, gives that Derek and the Dominos style Clapton tone, since he used an original Champ on that album.

I know at the same time, I was going to add Bass and Treble, but ended up not seeing a need for it, even my Mid knob stays around 6 all the time (which is the same resistance as it would be stock). Search around google, I remember someone had an explanation or which resistors did what in the tone stack.

EDIT: Here is the thread I used: https://www.ultimate-guitar.com/forum/showthread.php?t=782108
Last edited by Wylde_Life at Aug 5, 2011,
#7
the schematic is on the fender website.

http://support.fender.com/schematics/guitar_amplifiers/Champion_600_schematic.pdf


modification is extra easy.
-R20 and R21 makes a voltage divider, replace it with a 250kA pot with the middle (wiper) at the middle. this is the treble knob. when turned all the way to 10, the resistance for R21 should be 0.
-R22 is the bass resistor. use 250kA or 500kA here, 500k giving more bass. u can use 1M, but i think 250kA is enough. wire it as a variable resistor with one of the side lugs not connected. when turned all the way to 10, the resistance should be 250k (max).
-R23 is the middle resistor. use 25kB here, or 50kB for mega (read 'farty') mids. wire it as a variable resistor with one of the side lugs not connected. when turned all the way to 10, the resistance should be 25k (max).


this mod is somewhat practical, giving u flexibility. the circuit is pretty much there, with hard set value resistors, which is kind of lame. you can add a lot more, but i dont think that much work is necessary for this amp.
Call me "Shot".

ShotRod Guitar Works

Custom Hand-wired Amplifiers and Effect Pedals.

Est. 2007


Source to everything I say about Guitars, Pedals, and Amplifiers: I make them.


UG's Best DIY PedalBoard
#8
Dangit Shot you beat me to it haha.

Yeah basically what he said, the only thing I have to add is that R18 is your slope resistor, lower it for more bass and mids and raise it for less.
Guitars:
LTD F-50
Yamaha EG-112
'77 Harmony
Roadworn Starcaster
Gretsch G5120

Amps:
Vypyr 15
Epiphone Valve Junior combo
#9
Quote by ECistheBest
the schematic is on the fender website.

http://support.fender.com/schematics/guitar_amplifiers/Champion_600_schematic.pdf


modification is extra easy.
-R20 and R21 makes a voltage divider, replace it with a 250kA pot with the middle (wiper) at the middle. this is the treble knob. when turned all the way to 10, the resistance for R21 should be 0.
-R22 is the bass resistor. use 250kA or 500kA here, 500k giving more bass. u can use 1M, but i think 250kA is enough. wire it as a variable resistor with one of the side lugs not connected. when turned all the way to 10, the resistance should be 250k (max).
-R23 is the middle resistor. use 25kB here, or 50kB for mega (read 'farty') mids. wire it as a variable resistor with one of the side lugs not connected. when turned all the way to 10, the resistance should be 25k (max).


this mod is somewhat practical, giving u flexibility. the circuit is pretty much there, with hard set value resistors, which is kind of lame. you can add a lot more, but i dont think that much work is necessary for this amp.


To make sure I understand this right (sorry to jack a bit of the thread, this now has given me the urge to do some modding, lol): For the Treble pot, I would wire the top side of r20 to one of the outside lugs of the pot, the middle of r20/r21 to the middle lug of the pot (obviously, as you posted) and then the bottom of r21 to the other lug of the pot?
#10
if u ripped out the two resistors, ur left with three terminals. they go in order, with the output at the junction the of two resistors u had before. if rue going to do some modding, make sure u leve the amp off for a while, take out the power cord for a while, and Check the voltage across the filter caps first.
Call me "Shot".

ShotRod Guitar Works

Custom Hand-wired Amplifiers and Effect Pedals.

Est. 2007


Source to everything I say about Guitars, Pedals, and Amplifiers: I make them.


UG's Best DIY PedalBoard
#11
No, you take the resistors out, you're replacing the resistors with the pots.
Guitars:
LTD F-50
Yamaha EG-112
'77 Harmony
Roadworn Starcaster
Gretsch G5120

Amps:
Vypyr 15
Epiphone Valve Junior combo
#12
Quote by ECistheBest
if u ripped out the two resistors, ur left with three terminals. they go in order, with the output at the junction the of two resistors u had before. if rue going to do some modding, make sure u leve the amp off for a while, take out the power cord for a while, and Check the voltage across the filter caps first.


Ok, I thought that was it, just wanted to make sure. Thanks!
#13
Quote by grungebaby
No, you take the resistors out, you're replacing the resistors with the pots.


Sorry, I guess I wasn't clear, I realize that, I was just making sure I was wiring the pot the right way. I was just reffering to the R20/R21 as a reference point I suppose.

EDIT: Wait, Shot, isnt R19 the Middle Resistor?
Last edited by Wylde_Life at Aug 5, 2011,
#14
woops u caught me there buddy. I just assumed it would be numbered 23, but ure right. it's r19 that's the middle resistor.
Call me "Shot".

ShotRod Guitar Works

Custom Hand-wired Amplifiers and Effect Pedals.

Est. 2007


Source to everything I say about Guitars, Pedals, and Amplifiers: I make them.


UG's Best DIY PedalBoard
#15
Just did the Treble and Bass Controls (I already had the mid), thanks for the quick info Shot! Also thanks to the TS for getting my modding urge going, haha!

TS, I recommend doing this, very easy, I don't know much about electronics and only read basic schematics. Sounds great, I recommend just mounting them to the back panel, instead of cutting the back panel and adding a piece, I feel it looks better than in the video.