Author Topic: Mesa JCM800 restoration  (Read 6150 times)

marauder

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Mesa JCM800 restoration
« on: September 10, 2013, 04:31:45 AM »
Last time Phil came over from Hoboken to the homeland, he brought the last of his hurricane Sandy flood damaged pedals with him, a Mesa V-Twin.  This one is beyond repair :(  Corroded component legs, and pads, it would need everything pulling, and it's a nightmare to get the oxidised solder to melt,  only a pair of vactrols have been salvaged.  The board is still lying around in the corner somewhere , so if anyone wants it for the cost of shipping let me know , but I wouldn't bother to be honest.

Luckily the case is mostly stainless steel and survived ok, but the tread plate panel has suffered pitting corrosion, so has been painted.

Anyway,  the guts are now a JCM800 preamp circuit, with the second stomp acting as the lo and high input on the real amp.  The slider switch on the top switches a parallel 10k resistor on one of the existing 10k cathode resistors to give a little volume boost.

Phil wasn't bothered about some of the text being rubbed off, and said leave it as is, otherwise Haberdasher would have  been called upon to etch a face plate.

Somehow the Mesa 12AX7s survived with no ill effects, and are working well at the 190V the vero SMPS is supplying,  the best sounding tube pedal built by me or John.

Not good.




Lots of wiring.




JCM800 preamp.


9V in, 190V out.


A little repainting.


« Last Edit: September 10, 2013, 04:42:41 AM by marauder »

LaceSensor

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Re: Mesa JCM800 restoration
« Reply #1 on: September 10, 2013, 05:17:04 AM »
fackin bad ass man

kothoma

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Re: Mesa JCM800 restoration
« Reply #2 on: September 10, 2013, 05:19:42 AM »
Ouch, it really hurts looking at the first two photos.
It's a wonder the tubes survived.
What a great restoration job!

juansolo

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Re: Mesa JCM800 restoration
« Reply #3 on: September 10, 2013, 05:29:11 AM »
It does sound utterly spectacular. It murders the Twin pedal we did before. I think it's a combination of the extra voltage and using 12AX7s (which really don't work well at lower voltages). It really is a Marshall in a box now. Obv, dangerous voltages inside this one so don't undertake it lightly.
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lincolnic

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Re: Mesa JCM800 restoration
« Reply #4 on: September 10, 2013, 11:04:19 PM »
Is it bad that I see "9V in, 190V out" and I just want to laugh?

Terrific work, guys.

Cortexturizer

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Re: Mesa JCM800 restoration
« Reply #5 on: September 11, 2013, 02:31:26 AM »
when I saw 9V in 190V out I almost fell from my chair haha, AWESOME
pedal looks fantastic inside out, I don't have to hear it in action, I know it sounds like a dreamy marshall...

Darkknigh_t

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Re: Mesa JCM800 restoration
« Reply #6 on: September 11, 2013, 06:27:01 AM »
It looks amazing great job i love peoole who restore things :)

pickdropper

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Re: Mesa JCM800 restoration
« Reply #7 on: September 11, 2013, 07:04:27 AM »
Amazing restoration job, guys.  Very sharp.
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peterc

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Re: Mesa JCM800 restoration
« Reply #8 on: September 11, 2013, 01:08:33 PM »
Brilliant job. I like the 'wolf in sheep's clothing' idea.

How did you do the 12v - 190v conversion?

Peter
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culturejam

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Re: Mesa JCM800 restoration
« Reply #9 on: September 11, 2013, 02:10:58 PM »
Whoa. That is great work, man.

catfud

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Re: Mesa JCM800 restoration
« Reply #10 on: September 11, 2013, 03:26:59 PM »
Man, that's a great restoration, and I'm sure it sounds great in its new guise, but still, a damn shame about the Mesa V-Twin, that's also a lovely sounding pedal itself. I've seen the schematics for the Mesa V-Twin published somewhere too - and the circuit looked too complex for me to consider, but I wondered whether someone somewhere has done a DIY job using that schematic...

jkokura

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Re: Mesa JCM800 restoration
« Reply #11 on: September 11, 2013, 04:15:48 PM »
Now that is rad. I love repurposed stuff.

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billstein

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Re: Mesa JCM800 restoration
« Reply #12 on: September 11, 2013, 05:39:37 PM »
Top notch as usual.

juansolo

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Re: Mesa JCM800 restoration
« Reply #13 on: September 12, 2013, 01:39:40 AM »
Brilliant job. I like the 'wolf in sheep's clothing' idea.

How did you do the 12v - 190v conversion?

Peter

Using Rick Holt's 555 SMPS (http://www.diystompboxes.com/smfforum/index.php?topic=74088.120 Page 6-7). Though Cleggy has used a bigger inductor. Tried a Nixie PSU and it created a lot of noise for some reason. This one is not ideal on vero, but seems to work fine. It's been given a good long test.
« Last Edit: September 12, 2013, 01:43:55 AM by juansolo »
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hoodoo

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Re: Mesa JCM800 restoration
« Reply #14 on: September 12, 2013, 02:46:19 AM »
Geez, i wish You 2 were my mates that fixed my broken shit and made it better than new, awesome as always  :)