JCM 800 split channel mod ?

[Alexmc1988]

Hi I have a JCM 800 4210 and was wondering what mods I can do to make it sound better. It sounds very muddy compared to other 800s i have played. I have replaced the pre amp and the power amp tubes and I rebiased them properly. I have never modded an amp but I have modded effects pedals. I am currently downloading a video on how to service and overhaul amps so I hope that this will so me how to discharge the capacitors without killing myself.(Would I just have to touch them with like a screw driver that has a rubber handle?) Also I have trouble seeing what has changed in schematics. I was looking at Otto’s found in this thread http://music-electronics-forum.com/s...ead.php?t=5107 but it was just hard for me to tell what he had changed. I play a wide range of music. Any thing from John Mayer to Coheed and Cambria to Muse to Contemporary Christian Stuff. Any suggestions on mods and how to go about learning how to do them would be great.

Thanks,
Alex

[Alexmc1988]

OK so this older guy at work that used to have an electronics repair shop told me how to discharge the capacitors correctly and he said he would help me out a little with doing some mods. Now i just need to know what to. Any suggestions?

[Tubis]

First learn what every little bit in the original circuit does to the sound before starting to modify it to your taste.
This model is very differnt from say an 2203. It has the eq before the distortion stages and it has a diod clipping distortion stage that i always remove. That has no place in a tube overdrive amp, finito.

[Alexmc1988]

ok so I found this page. http://www.tone-lizard.com/Ultimate_JCM800.htm I was wondering if these mods can be doen to the 4210. I didn't know if it is close enough to the 2203/2204 or not. If I can do these I will still need something to improve the clean channel.

[Alexmc1988]

OK so I am fully confident that I can Otto's mod. I have gone threw the schematics and highlighted all of the changes that I can find. I must admit this is a bigger mod that I thought it was going to be but I am still confident. I have all of next week off and then I am moving back to school so I will have time to work on it. I know how to discharge the amp by placing alligator clips on the first pin of a pre amp tube then on to the chassis or some other ground. I am just having trouble following the schematics. For one Are the letters, such as "A" were the lines just stop will I make a connection to a solder pad or trace there and the then trace goes to where the other "A" is? I am also not sure where I will have to cut the board. It looks like the reverb is cut out of the signal switching. Will I still be able to turn the reverb on and off with the foot switch? Also I to am having trouble reading a lot of the values are you sure you can't just make a parts list? Also is there additional information on the hand drawn schematic? It looks incomplete to me and I don?t know what the "TS" with a circle around it means. Also what wattage of resistors will I need and do you suggest metal film caps and resistors like with effects pedals?
Thanks Alex.

[otto]

Hi Alex, I'm pleased you are interested in my mod.
Write to me if you need help.