Marshall Neanderthal by Ivanberg - Build Thread:

[Inspector #20]

@syscokid and @ivan H were super kind and helpful during the Marshall Origin Headfirst/Ivanberg Modifications. Their collective knowledge is really amazing and I'm grateful for their help on the Origin project.

Recently, i killed my 1993 Valvestate Bi-Chorus 8200, and I was thinking outloud about maybe purchasing a hand-wired Marshall re-issue and @syscokid suggested we build a 50 watt Master Volume from scratch with only the very best, USA components.

The proposed build would feature a Metro FX Loop and a resonance control in place of the voltage selector.

It will use 6550 power tubes and CV4004 preamp tubes, plus will be custom voiced.

Parts are already arriving and we will post updates soon....

 

[Don O]

What happened to the Valvestate?

 

[syscokid]

What happened to the Valvestate?

Yes, I was wondering too. I'm betting that it's something simple to diagnose and fix!

 

[Inspector #20]

What happened to the Valvestate?

Yes, I was wondering too. I'm betting that it's something simple to diagnose and fix!

I went through the 8200 Valvestate and found nothing visibly wrong. I changed the tube to no avail. I was unable to get any components to respond to light chopstick tapping. The "rushing wind" sound persists.

I'm afraid the 8200 might be a write-off.

 

[syscokid]

I'm afraid the 8200 might be a write-off.

 

[Inspector #20]

View attachment 81483

I'm kinda at the point where I'm suspecting filter caps, PCB, which are both way outside my skill level and equipment.

 

[Don O]

I'm kinda at the point where I'm suspecting filter caps, PCB, which are both way outside my skill level and equipment.

I can certainly take a look it. I got meters, o-scope and a function generator. I also have the 8280 to compare it too.

 

[syscokid]

I'm kinda at the point where I'm suspecting filter caps, PCB, which are both way outside my skill level and equipment.

I can certainly take a look it. I got meters, o-scope and a function generator. I also have the 8280 to compare it too.

This is a real good idea. You guys are practically neighbors!

 

[Amp Mad Scientist]

I'm kinda at the point where I'm suspecting filter caps, PCB, which are both way outside my skill level and equipment.

You should send it over here so either Sysco or I could fix it.
But I don't understand why techs at FMIC couldn't fix it just as easily.

Recap, new jacks, is a good idea when the amp is so old. But new caps don't cost very much either.
I think we could fix it if nobody else will.

 

[Inspector #20]

You should send it over here so either Sysco or I could fix it.
But I don't understand why techs at FMIC couldn't fix it just as easily.

Recap, new jacks, is a good idea when the amp is so old. But new caps don't cost very much either.
I think we could fix it if nobody else will.

No doubt!

 

[Inspector #20]

I can certainly take a look it. I got meters, o-scope and a function generator. I also have the 8280 to compare it too.

That's mighty kind of you, Doc..

The 8200 and 8240 use the same schematic, that much I do know....

 

[Inspector #20]

Cabinet ordered from Guitar Cabinets Direct.

Marshall Black Elephant Tolex with a Red Elephant Tolex front panel, gold piping and gold handle.

 

[eSGEe]

I can certainly take a look it. I got meters, o-scope and a function generator. I also have the 8280 to compare it too.

you know you have a FLUX CAPACITOR --- admit it

 

[Don O]

you know you have a FLUX CAPACITOR --- admit it

I’ve been soldering since I was 6 years old. I don’t advertise fixing stuff since I’ve been doing that my entire career (under the radar). I still have schematics I drew in the 70s.

 

[Inspector #20]

Parts arriving....







We opted for toggle switching as opposed to the lighted Rocker switches with a custom front panel.

 

[Inspector #20]

Transformers are 12 weeks out, but will be supplied by Marstran. Order is now confirmed.

We are using a Drake 784-139 type output transformer Drake 1202-118 type power transformer.

Exciting news!!!!

 

[Inspector #20]

Today's progress!!!!

Resonance control replaces the voltage selector switch...

 

[Amp Mad Scientist]

Parts arriving....

View attachment 81512

View attachment 81513

View attachment 81514

We opted for toggle switching as opposed to the lighted Rocker switches with a custom front panel.

Before I put any parts on the chassis,,,
The first thing I do is solder the ground lugs to the chassis. (instead of just a nut bolt washer) You will notice that Fender does this too, if you study the amps of olde..
The ground lug is held in place by the screw when you solder it...

A good solder temperature is about 1000 degrees F.
I use a heat gun to pre heat the chassis, followed by a soldering iron w/ a big fat tip to flow the solder.

But I'm sure fender used American Beauty when they massed produced the older amps.
You know what American Beauty is?

 

[Amp Mad Scientist]

Today's progress!!!!

Resonance control replaces the voltage selector switch...

View attachment 81597

View attachment 81596

Of course with an aluminum chassis, you can't solder to aluminum.
You need a steel chassis to do that soldering.

 

[67plexi]

I have a Dagnall transformer set for my next green hornet build my friend in Italy scored me a NOS 784-139 box dated 1968