EVH Chassis Layout

For all things to build the brown sound

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mightymike
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EVH Chassis Layout

Post by mightymike » Wed Nov 02, 2005 4:16 pm

Here's 3 eyewitness accounts:

(1) By Mark Cameron by pictures taken in the early 80'S.
There ARE small tone altering and/or gain altering mods.
I do have pic's so I CAN physically see that the amp has a split cathode arrangement.
...the cap on v2(330uf) cathode.
...its a 2.7k/.68 and the resistor looks like the stock part(but I don't think it is)but the cap is one of those yellow square type from the 70' Marshall's. From the circuit card It looks like it came stock with this arrangement. The post that is pressed in looks stock too witch tells me more than anyone could.In the pics the serial # is 12301.


(2) By C errem. 1980.
To try to wrap up is ED thing...
His head was a 67/68 and he had the first stage valve with BOTH cathodes tied together sharing the same 820 ohm resistor that was bypassed with a 330uF blue cap...

His treble cap was a round shaped ceramic that was a 250pF that said MURATA ... With 56K on the tone circuit feed..

One of the 470K mixer resistors was bypassed with a round hollow tubular MURATA cap 500pF... If memory serves me right on the value, or it was a 330pF..I will check my notes....

The real kicker, his phase-inverter "get-rid-of-the-FIZZIES" cap was a 100pF instead of the normal 47pF ....and this my friends is how the "brown sound" with that added compression happens..

Oh, BTW those 820 ohm resistors were carbon-comp and drifted in value up about 1.1K and make the amp much more gainy and warmer, since these re-bias the 12AX7 valves in a bit more non-linear region..

I am pretty sure the feedback resistor was a 47K ...I will have to check my notes...

The filter cap in the center of the board was a dual 16uF gray RS cap...

The screen filtering was 2 DALY 32uF light-blue caps in series... The voltage doubler were 2 100uF DALY royal-blue caps...

Rear cap on top of chassis was a royal-blue HUNTS 32uF or 16uF...need to check notes..

The value of the coupling cap between V1 and V2a....022uF.

At least that was what it was in 1980...


(3) Plaap (a friend of Peter Van Wheelden who restored Eddie's amp.)
Edwards amp's internal measurements were as follows:

1.The first 820 ohm resistor (carbon type) measured a little over 1K. It was bypassed with a blue 330uF resistor. can

2.His treble cap was a 250pF Murata flat ceramic one. The cap across his 470K was a Murata hollow round 330pF. cap

3.His second stage 820 ohm (which also measured a little over 1K, was also bypassed with the exact same type 330uF blue colored cap that was on the first cathode resistor.

4.The filtering caps for the middle of the board were gray colored RS caps that had dual 16uF values.

5.The screens were 2 blue caps in series (DALY 32uF's).

6.The voltage doubler were two big blue caps (100uF DALY's). The one on the outside was a blue Daly - and was a single 32uF.

7.The feedback resistor was a 47K of unknown origin.

8.His power transformer was the smaller one of that era. His OPT was also the smaller one with 1.5" stack.

The amp was either left stock into a load resistor or, a big Ohmite(or other) power resistor was placed somewhere in the circuit to cut the power of only the output stage meaning Sylvania 6CA7's were the only valves to hold up to this.

If this is true - doesent this kinda dispel the whole 'special' 67 slp 100 myth ...as almost all amps of that year had pretty much identical configurations (with the small exception of the 330uf cap on the second preamp stage?

Dankuwell !(dutch for many thanks)
Plaap

Update: 12-10-14
I have a 3 version animation I drew up a while back. It plays in this order: C errem's description, Stock67 (With Split Cathode), and Ralle Spec (as it was back in 2005).
http://www.mediafire.com/view/i4z59v958 ... mation.gif

If you watch it changes to the different specs, and reveals under board wires. The way to tell which is which: The Ralle Spec has the 4 100uf Caps on the Power Board, and the C errem Spec has the 100pf fizzy cap at the Phase inverter instead of a 47pf, and the other is Stock.

Warning: there where some mistakes in my drawing. I fixed them, but when my Desktop died all I could find was this older one.

1) Missing Green wire on V3 PIn2 goes to the 1 meg on the board to the left of the 470 ohm resister on the board. I forgot to draw it in.
2)One of the input jacks is wired wrong.See how I ran the black wire to the wrong terminal on the jack
on the bottom left? The one to the right of it, is how it should look.
3)and on one of the 1.5 K resistors on the Power tubes are to the wrong terminal on the right side

If you open the file up in a Graphic program you can see each frame and print individually
Last edited by mightymike on Wed Dec 10, 2014 3:50 pm, edited 1 time in total.

Billy Batz
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Post by Billy Batz » Wed Nov 02, 2005 4:24 pm

Good stuff tp put here
Last edited by Billy Batz on Wed Nov 02, 2005 4:49 pm, edited 1 time in total.

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VelvetGeorge
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Post by VelvetGeorge » Wed Nov 02, 2005 7:03 pm

The chassis alyout in EVH's amp is the same one used in the 67/68 bare bones kit available in the store. One cap on top, 1.5" OT ect.


George
Check out Plexi Replicas for my personal amp builds...
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rockstah
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Post by rockstah » Wed Nov 02, 2005 7:22 pm

which variation to try first.. hmmmm:)

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Flames1950
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Post by Flames1950 » Wed Nov 02, 2005 11:07 pm

As I pointed out on that post at PlexiPalace, I'm 99% sure that ****** also posted once that he saw that amp a little later and it had been converted to split cathodes on V1. I thought the John Suhr thread at Gear Page or wherever detailed split cathodes whenever John saw it.

Do you ever wonder if, like so many things Eddie doesn't like 'fessing up about, there is not just one "magic" Marshall? The differences in accounts of sightings almost make it seem as if there was the original amp, and then he found at least one more that he liked as well and used too, but he'll never tell?
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Post by Billy Batz » Thu Nov 03, 2005 7:43 am

Im perfectly ready to buy that/ Especially seeing how stock all of the alleged values are. That large wattage resistor accross OT primaries trick is cool but I dont think thats necessarily the best VH tone. It does sound instant VH1 though. But dangerous apparently.

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Post by clarkydaz » Sat Nov 05, 2005 7:54 am

how much of the 'magic' is a very good sounding marshall with the production of the first album? Ralles's clips account for the produced sound, (which may make it better?)

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Post by guitar007 » Thu Nov 10, 2005 9:01 pm

Hey, guys..this is my 1st post. What a great board! Now on to my question...mightymike, what software did you use to create that image? It Rocks!
~guitar007

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mightymike
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Post by mightymike » Sat Nov 12, 2005 5:35 am

Thanks Guitar007
If you like this kind of stuff, check out Billy Batz's drawings too. He's a wiz with that Photoshop program.

I used George's 68 Layout Board as a base, changed the values, and then drew the rest with Paint Shop Pro 7 (which a poor man's Photoshop) I'm still learning, and that's why its a little blurry.

Hey Dan, I just bought the Adobe Suite.
Hope you don't mind if I hit you up for a few pointers
once I get her up and running.

Billy Batz
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Post by Billy Batz » Sat Nov 12, 2005 7:22 am

Go ahead. Im no pro. Those layouts are the best I can do graphically and I probably did a lot of it the hard way because I dont know th eprograms as well as I should.

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mightymike
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Post by mightymike » Sat Nov 12, 2005 7:45 am

You're being modest. I saw some of your latest stuff with the 3d effects you've added to your repitour. They're the bomb.

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Post by Billy Batz » Sat Nov 12, 2005 5:03 pm

Mike I still cant get that to work when I link to it?

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mightymike
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Post by mightymike » Sat Nov 12, 2005 5:41 pm

The file won't play if you open it with your photo editing software, that you probably have .gif associated with. The program will think it's only one image.

I just double left click the link, and it opens in a new window in explorer. But if you have a slow connect, then you might want to right click the link, and choose "save target as" to download it. After you download it, then right click the file, and chose "open with", then choose windows explorer, Netscape, or Windows Picture and fax Viewer,

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Post by Guest » Sat Nov 12, 2005 6:43 pm

Hey Everybody. Excellent idea for a forum! Glad this was set up :-)

I got a question about the mightymike chassis layout diagrams. Are the 1.5K resistors on the power tubes in the right place? According to the schematics I know of it looks like it should be like this: ( I made the resistor leads green to stand out)

Image

Instead of this.

Image


Or is that how it's actully hooked up in Ralle's amp? (you never know what happy mistakes might give good tone) Anyway, Though I would inquire into if anyone's amp is actully wired like this and does it sound good before I started experimenting and blowing things up. Thanks! -Clay

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mightymike
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Post by mightymike » Sat Nov 12, 2005 7:24 pm

Shit, glad you caught that.
Guess I have some updating to do.
The link will be back up, with the fix asap.

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