NAD - Reverb dumpster dive

[fitz]

Picked this '97 Marshall JCM600 chassis out of the parts only bin on Reverb last weekend.

Listing said:
"Operational Condition: The clean channel works as intended while the distortion channel has very low volume. The shaft of the "presence" control on the back of the amp has been broken and will need to be replaced."




Amp arrived Thursday and I tried all the easy stuff.
Power tubes are TAD EL34B and the Preamp tubes are 2 JJ ECC83S & 2 unlabeled tubes - one appears to be a long plate.
Suspecting a possible bad preamp tube might be part of the OD channel volume issue, I just put in 4 known good JJ's from the stash.

Deoxit gold on all the pins and some D5 in all the pots and jacks.
OD channel volume issue is still as described - very low volume, but audible.
Volume and gain on the channel function at said low volume.
All the tubes light up and the normal channel seems, well, normal.



Hooked up a Zoom gizmo and the loops are both working as they should.
Running it through a 212 of V-Types with some TBE in the series loop and a little front-end dirt from my on-board Hondo OD it sounds fantastic.



Nothing visibly apparent as burned out, and there does not look like any tube heat damage to the boards or sockets.
Came without the reverb tank, but I got one ordered from T&M along with a new presence pot & some hardware for a head shell build.

 

[fitz]

Had another look around today and found this loose wire...

Connected to the tube board at W111:

And there was this lonely hole in the front pot board at W3:

So, I scanned the downloaded schematic for those board numbers and came across this:

Apparently, that wire from W111 goes in that hole at W3...

Took off all the pot & jack nuts and wiggled out the front board to get at the back side.
Hit the wire with the iron and a dab of solder for good measure.
Wiggled the board back in, put the tubes in and fired it up.

It's a 2 channel amp again!!!

Can't wait to get the presence knob in and the reverb tank.
Now I just need some matching cabs...

 

[fitz]

While I'm waiting on parts, I got started on the head shell build.
Scrap wood from my stash.

A little router action and some sanding.



Also found a tube cage on Reverb, so that's inbound too.

 

[Amp Mad Scientist]

Had another look around today and found this loose wire...
View attachment 88542
Connected to the tube board at W111:
View attachment 88543
And there was this lonely hole in the front pot board at W3:
View attachment 88544
So, I scanned the downloaded schematic for those board numbers and came across this:
View attachment 88546
Apparently, that wire from W111 goes in that hole at W3...

Took off all the pot & jack nuts and wiggled out the front board to get at the back side.
Hit the wire with the iron and a dab of solder for good measure.
Wiggled the board back in, put the tubes in and fired it up.

It's a 2 channel amp again!!!

Can't wait to get the presence knob in and the reverb tank.
Now I just need some matching cabs...

So how much $$$ did you pay for it?

 

[fitz]

So how much $$$ did you buy it for?

$175.
But it came without the reverb tank and I "negotiated" a $25 refund to cover most of the cost of the one I got from Tubes & More.
Tube cage was another $27 and I got about $25 more in corners/handle/feet stuff from T&M.
Tolex / grill for the head and pending pair of 1x12 cabs will run about another $100.

 

[Thatbastarddon]

Wow @fitz ! Good job! You lucky so and so!

 

[steveb63]

Congratulations
Nice score.

Your ambassador title should be Amplifier Macguyver Advisor.

Way to get it up and running.

 

[Mitch Pearrow SJMP]

Complete score brother
Congratulations
Nice dive retrieval

 

[fitz]

Congratulations
Nice score.

Your ambassador title should be Amplifier Macguyver Advisor.

Way to get it up and running.

That loose wire was a blind squirl moment for me.
I'm an accountant, I ain't no MacGyver amp tech...
But my numbers brain says all in for about $350-400, and I'll end up with a nice little 60w Marshall rig.
Lifelong wood working hobby, so the cab builds are my favorite part of the process.
I got all the reclaimed plywood I'll need for a pair of 112's (3/4" ~ 11 ply BB) and I have a choice of speakers in the stash.

 

[Jethro Rocker]

Wow! Very cool!!
It will look stellar when done too I will bet.,

 

[Session 5]

Congrats! nice score..

 

[DirtySteve]

Just awesome!

 

[guitarweasel]

Nice!

 

[steveb63]

That loose wire was a blind squirl moment for me.
I'm an accountant, I ain't no MacGyver amp tech...
But my numbers brain says all in for about $350-400, and I'll end up with a nice little 60w Marshall rig.
Lifelong wood working hobby, so the cab builds are my favorite part of the process.
I got all the reclaimed plywood I'll need for a pair of 112's (3/4" ~ 11 ply BB) and I have a choice of speakers in the stash.

It's better to be lucky than good most times anyway. Lol.

Just always appreciate bringing old gear, tools whatever back to life.

I would rather have something I "Macguyvered" and brought back to life, than a new toy any day.

Hell, I use a homemade wooden hammer my Father and I made about forty years ago, instead of a fancy new one made out of old PRS offcuts!

 

[syscokid]

Very cool, Mr fitz! You da man…

 

[Inspector #20]

$175.
But it came without the reverb tank and I "negotiated" a $25 refund to cover most of the cost of the one I got from Tubes & More.
Tube cage was another $27 and I got about $25 more in corners/handle/feet stuff from T&M.
Tolex / grill for the head and pending pair of 1x12 cabs will run about another $100.

Need a Reverb Tank???

 

[fitz]

Need a Reverb Tank???

Already got one inbound that matches the OEM Marshall specs for the JCM600.
Thanks, if you were offering - the one from Tubes & More was $27.95, and I got $25 back from the seller.

 

[Inspector #20]

Already got one inbound that matches the OEM Marshall specs for the JCM600.
Thanks, if you were offering - the one from Tubes & More was $27.95, and I got $25 back from the seller.

Mine was an Accutronics from a 1997 Valvestate - date coded

 

[Clockworkmike]

That's a helluva score, to only have to do that minimal work and fix it! The JCM600 was actually a really cool amp that got next to no attention when it debuted almost at the exact same time as the JCM2000 series.

They were essentially replacements for the JTM60s that were retired the year before but with some more modernesque tweaks and apparently fixing the overheating problem some of the JTMs unfortunately suffered, while borrowing a lot from the JCM2000s EQ design

Definitely a classic Marshall tone, akin to the Plexis

 

[fitz]

That's a helluva score, to only have to do that minimal work and fix it! The JCM600 was actually a really cool amp that got next to no attention when it debuted almost at the exact same time as the JCM2000 series.

They were essentially replacements for the JTM60s that were retired the year before but with some more modernesque tweaks and apparently fixing the overheating problem some of the JTMs unfortunately suffered, while borrowing a lot from the JCM2000s EQ design

Definitely a classic Marshall tone, akin to the Plexis

Thanks.
The PCB boards in it are all stamped JTM60.
I'm going to keep it inverted in the headshell like the pics above - keep the tubes on top.

Closest thing I have to compare it to is my DSL20, although it has a smoother clean channel that breaks up to a more classic tone with volume, and the overdrive channel is a lot like my 5010 cranked, but with a definite tube feel and way more volume on tap.
Keep in mind, I still have to replace the presence pot, and I have no idea what the snapped of shaft is set at.

I tried running through another 212 cab with V30's today, but I think I like the V-Types better with this amp.
I also have a pair of T-75's in the closet that I will give a try when I get the new cabs made.
I'd love to run it through some greenbacks, or H-30 anniversaries I have, but I might like it too much and worry about the power handling when it's cranked.