MARSHALL JCM900 MKIII 2500 HEAD...

[cliffenstein]

Just picked up a 1990 MkIII 50w head. I've been reading about these for a long time and neglected to pull the trigger when they could have been had for a pittance. I Decided to do so for a "good deal" in today's dollars ($999 with no tax). It came in yesterday and I've been putting it through its paces (complete with the jumpered loop trick which really DOES make quite the difference!). Appearance is average I'd say for a 33 year old amp head, but today I opened it up and took out the chassis...looks totally unmolested and the wiring looks quite clean, all things considered. I'm dropping it off with my tech on Friday for a bias, cleaning, and a replace/repair anything that needs it. I'm really REALLY liking this amp as it is...I very much look forward to getting it back after it's truly ready.

If you're knowledgeable and see anything in the pics below that you think needs attention, replacing, or upgrading, please let me know. If C8 is the bias pot resistor then that means it has the proper 22uf resistor in place so biasing to 40-42 should be doable.

PICS:

[***1776***]

HNAD and congrats - I had one for a short time and had no issues with the amp, it sounded just fine and i would rock one again if needed. These use to be about $600 all day long just a couple years ago lol, of all the 900 series i liked the SLX a little more, but the MKIII 2500 was solid with good tones IMO

Want to see how you feel when she comes back from the tech

[GuitarBilly]

These amps are killer. Congrats!!

I don't see anything wrong or in need of replacement. Let's see what your tech says after testing it but nothing jumps out at me from the picture

[cliffenstein]

These amps are killer. Congrats!!

I don't see anything wrong or in need of replacement. Let's see what your tech says after testing it but nothing jumps out at me from the picture

My thoughts exactly...I think I'm simply in for a biasing and a cleaning and that's it.

[cliffenstein]

HNAD and congrats - I had one for a short time and had no issues with the amp, it sounded just fine and i would rock one again if needed. These use to be about $600 all day long just a couple years ago lol, of all the 900 series i liked the SLX a little more, but the MKIII 2500 was solid with good tones IMO

Want to see how you feel when she comes back from the tech

Let's see...we paid people more for staying home than for working for several years and then we forced fast food joints to pay employees $15 an hour and wonder why everything is now twice as expensive! So yeah...I hear ya! I got my first year (1997) JCM 2000 DSL100 (also a marvelous amp!) for just $380 in 2016.

[_ej_]

Congrats dude. The single channel 900s are my favorite Marshall.

[thermionic geek]

Congrats! These are great amps. I had one years ago and traded mine for my beloved SLX. I liked dialing a medium grind that I could clean up with a volume knob and then boosting it with either a Boss Eq pedal or a Tube Screamer.

[cliffenstein]

I’ll be getting it back from my tech sometime next week. After new tubes (pre and power), I could already tell that it’s not gonna need the sensitivity knob on at all after biasing.

Totally killer.

[colejustesen]

I much preferred the 2500 MkIII to the SL-X I had. Granted the SL-X was the 5881 model, and the MkIII was EL34. To date, the MkIII has been my favorite Marshall that I have owned. I have never owned a JCM800 or a Plexi, so bare that in mind, but it was still pretty sweet when I had it. I sold it to fund a Laney GH50L; which was great too.

Cole

[cliffenstein]

Got the amp back...didn't need the resistor change like a lot of them did, as it already had the proper 47k bias resistor in place. So all my tech had to do was general cleaning and and it biased right up to 70% no problem.

Amp sounds totally killer...I absolutely love it.

[MacaroniSalad]

Sweet! Always nice when its less work than you expect.

I would really like to check one of these out.

[cliffenstein]

Okay...first band practice with this Marshall MKIII 2500...my gosh, what a sound, what a feel, what a joy to play through. It's my favorite amp now. Gonna take it for a trio of midwest shows I'm playing this weekend (Ohio, Indiana, Wisconsin). It's interesting because it's said by various people that this is "the same circuit as the 2204 with a built in tube screamer." I dunno...can it be the same circuit when the tone stack is like a Plexi, not a 2204? Just like a Plexi you gotta turn the bass knob all the way up...the 2204 and 2203 have a more responsive tone stack. Also, this 2500 has a better volume sweep...it has whisper quiet to roaring loud with everything in between capabilities...the 2204 and 2203 go from nothing immediately to super loud. Also there's no choke...this has as a resistor that does that job (all the JCM900 models are that way, as are the JCM 2000's).

Blah blah blah...the amp is killer!!!!!!!!!!

[colejustesen]

I forgot, it didn't come with a choke. That was a modification I did on mine. It improved the feel for me, not really the sound, and made it feel slightly bigger and dynamic. Definitely not a needed mod, but I liked the change it gave me.

I am glad you are loving the amp, it really is special. I will say again, this is my favorite of the JCM900 line.

Cole

[GuitarBilly]

Yeah I was just looking at the schematics and the 2500 is very different from the 800s. They're their own thing.

The preamp looks a bit like 2205/2210 but those have a different output section. They're both killer amps.