More stuff to my Jcm-800

[Sanguis]

hello, I whas wonderin about if any one can help me, add an effect loop, a extra gain stage, responce nob, a mid shift and a second channel.

Her is a shematic you kan use
http://bwilliamson.home.mchsi.com/schems/marshall/2203-800s.gif

[Johan]

...as helpfull as this crowd is, I think you will get better responce over at ampage with these questions.

if you want my opinion.
the JCM800 is closing in on becoming a vintage amp and the mods you are talking about is quite exstencive, you probably need to drill extra holes for the responce and midshift pots as well as for the FX-loop.  all of this will lower the value of the amp.
why dont you just trade it for something like a JCM900 SL-X  ( 90's two channel hi-gain Marshall based on the 2203.. ) or something?...
..here in Sweden at least, a swap like that would also leave you with a little extra cash in your pocket...

Johan

[Dai H.]

ultimately it's your choice, but I agree with Johan. Sell it and get something you really want. Mods like that can reduce the value, be unsightly and cause problems if not done well.  Also, is it serviced and in good condition? Any leaky caps, bad or weak tubes? Is it biased correctly, etc.? Maybe it just needs some service.

[lovekraft0]

If you've got a real 2203 Master volume, and a boost pedal in front of it won't get you enough gain, then trade it for a 5150 or something - don't screw it up trying to make it something it'll never be.The only problem with a stock JCM800 is that they only sound really good at high volume - set the master between 3 and 4 o'clock, and they wail!!

[Kleber AG]

The only problem with a stock JCM800 is that they only sound really good at high volume - set the master between 3 and 4 o'clock, and they wail!!

ughhh... mine has 100W, 2203 that's just not possible in home  :cry:

Kleber AG

[william]

MMMM, 5150, I kind of love mine.  I'd avoid messing with the JCM800.  If you MUST modify it, build one, then modify that one.  That's what I'm planning to do.

[vanhansen]

I agree with everyone else's opinions on this.  The JCM800 2203 is just not an amp you want to go modifying these days.  They're too sought after and becoming valueable.  Any mods will hurt that.  I would love one myself but am very happy with my JCM900 2100 MkIII (pre-SLX) amp.  It has an effects loop.  It's not really a two channel amp, but more a 1 channel amp with two master controls (channel B for boost).  Mine was made in 1990 which is the year it was introduced.  And like it was said earlier, it's a high gain version of the JCM800 2203 and 2204 models.  If you can find one of those, you'd be in good shape.  I paid under $500 for mine used back in 1995-96.

Service your 2203 to keep it in tip top shape and just hang on to it.  It's quickly becoming a classic, if it hasn't already.

[lovekraft0]

ughhh... mine has 100W, 2203 that's just not possible in home  :cry:

Yeah, it's not an ideal bedroom amp - have you tried a THD Hot Plate, or a Weber MASS, or any other attenuator? They're not perfect, but they're not all bad!

[Kleber AG]

Nope, never tried something like that...

I may try to just get it going with a pair of the tubes (50W), still not a bedroom amp, it never will be :lol:

I removed the hi-pass cap (1nF) on the preamp vol, but a long time ago, not sure what it have improved or not.

I'd like to try JC M."viva analog" JCM800 MODs, I have it saved here but it seems to don't be on line anymore? Had anyone tried that MODs, they're kinda not so simple MODs but I'd try that if someone (JC?) could say it's worth...

Thanks
Kleber AG

[Danny G]

There are some reversable mods you can do to an 800.  

They have a brite cap on the volume control--a 470 pf-ish ceramic cap.  Clip one leg, and say goodbye to thin tone at low volumes.  

Also, you can replace the cheapo box caps with high quality Sozo caps (replicas of the old Mustard caps).  More of a parts upgrade than a mod.  The JCM800 2203 board is designed to take caps of many sizes for certain values.  They really smooth out the tone.

Both of these tweaks are 100% reversable, but really smooth out the tone of these wonderful amps.