Boss MT-2 Metal Zone Schematic

[anotherjim]

Correcting U02a inversion?
Those 10p caps over 22k are either the designers go to stability/anti rf or place holders in case more high cut was needed. You could fit anything up to 330p in lieu of 10p if you want without cutting any high end -  and maybe you wouldn't know if you left them out altogether?

[nickbungus]

Well I have a working board.  As predicted I made a few silly mistakes that have now been corrected and I'm going make another one this week.

Theres a few things which I need to address before I make a final version:

• Get each set of Pot pads together and on the board edge
• Look at the physical size of the caps.  All the electros are occupying too much space and some of the others are too

Anyway the board is 52mmx 100mm


And the layout:


And the bom:
Ref Name   Component   Value
C001   Capacitor   10uF
C002   Capacitor   10uF
C005   Capacitor   10uF
C008   Capacitor   220nf
C009   Capacitor   47n
C010   Capacitor   10p
C011   Capacitor   1uF
C018   Capacitor   10p
C019   Capacitor   100uF
C020   Capacitor   220nf
C021   Capacitor   1uF
C022   Capacitor   47p
C023   Capacitor   15n
C024   Capacitor   15n
C025   Capacitor   1n5
C026   Capacitor   100p
C027   Capacitor   10uF
C028   Capacitor   47p
C029   Capacitor   33n
C030   Capacitor   10uF
C031   Capacitor   47n
C032   Capacitor   100p
C033   Capacitor   15n
C034   Capacitor   27n
C035   Capacitor   10n
C036   Capacitor   22n
C037   Capacitor   1uF
C038   Capacitor   100n
C040   Capacitor   100uF
C041   Capacitor   100uF
C042   Capacitor   47nf
C043   Capacitor   8n2
C044   Capacitor   10n
D003   Diode   1n4148
D004   Diode   1n4148
D006   Diode   1n4007
U01   Opamp   TL072
U02   Opamp   TL072
U03   Opamp   TL072
U04   Opamp   TL072
R001   Resistor   1k
R002   Resistor   10K
R003   Resistor   100K
R004   Resistor   100K
R012   Resistor   2k2
R013   Resistor   100k
R014   Resistor   22k
R015   Resistor   22k
R024   Resistor   10K
R025   Resistor   470k
R026   Resistor   22k
R027   Resistor   470ohm
R028   Resistor   22k
R029   Resistor   100K
R030   Resistor   3k3
R031   Resistor   4k7
R032   Resistor   10K
R033   Resistor   2k2
R034   Resistor   1K
R035   Resistor   47k
R036   Resistor   47k
R037   Resistor   10K
R038   Resistor   47k
R039   Resistor   1M
R040   Resistor   100K
R041   Resistor   1K
R042   Resistor   10K
R043   Resistor   100K
R044   Resistor   220k
R045   Resistor   10K
R046   Resistor   2k2
R048   Resistor   2k2
R049   Resistor   330ohm
R050   Resistor   330ohm
R051   Resistor   1K
R053   Resistor   47k
R054   Resistor   10K
R056   Resistor   10K
R057   Resistor   10K
R058   Resistor   1M
R059   Resistor   10K
R060   Resistor   10K
R061   Resistor   2k2
R062   Resistor   2k2
CLR    Resistor   2k2
Q001   Transistor   2N5088
Q007   Transistor   2N5088
Q008   Transistor   2N5088
Q010   Transistor   2N5088
Q011   Transistor   2n5457, 2n5484 etc

[bloxstompboxes]

Good work Nick! You'll get it.

[nickbungus]

Cheers Eric.  My v1 is built and works although I totally messed up the transisitors (fixed in the above layout) and also, I got a lot of lifted pads as I used some old copper clad board that had been printed on and then rubbed off. 

I've just bought some new board so I'll be on it again soon.  I think I'm going for the Deizel Mod with this one

[nickbungus]

Heres my V2 board. Unverified (update: Verified!) as I'm just on the vinegar strokes now but I'll report within the next couple of days.

I've got all the pot pads next to each other but it I've now had to add a couple of jumpers.  Still I reckon I can squeeze it home into a 1590b.

The sizes are 52mm x 94.5mm

[bloxstompboxes]

Liking this one better nick. I started to do my own the other day and realized I wasn't interested enough to go as far as designing my own board for this pedal when I already have an original and there are a couple of layouts available already. I'd like to know when and if this latest layout works. I'll give it a go when you've verified it.

[nickbungus]

Hi Eric

I've just finished it bar the boxing and its 100% working.   

I used a dual Linear pot (B) instead of the Reverse Log (C) for the parametric mids and will probably change it as its only useful in the last third.

Sounds awesome for bedroom metal (I actually love the fact so many people hate this pedal!).  Dont know if its because I built it myself or because my practice rig is better or its just a bit better with the modern subs (ICs and trannies) but to my ears it sounds better than what I remember my original sounded.

I'll post the board size and also an alternative version that I didn't do a copper fill on.  I actually made the one without the copper fill but etched a filled one too.  I'll use this one for my modded version.

For this version I thickened the traces and the pad sizes. 

Chuffed to bits that it works!  

If you want Eric, I'll send you the DesignSpark files, if you want to make some improvements.  Don't know if you've ever used it but its free, quite straight forward and the files can be converted to Eagle.

[bloxstompboxes]

That's cool nick. Don't bother with the files unless anyone else is interested. Please do let me know the dimensions of the board though.

Sucks about the pot. All I could get was a dual linear as well. Bought several the other day just for this build. Thinking maybe of trying this stock first, compare it to my original, and then with a few mods. There are some I found that are supposed to get rid of the harshness and better the tone control. There is a guy on youtube.com I like to watch who does guitar builds and has modded this pedal. CSG guitars I think is his brand and his name is Collin, maybe. I think he is in the U.K. somewhere. Good shredder and funny to watch.

I like how everyone hates this pedal too. Then you look on ebay and all the reviews are mostly positive, from what I remember. Agreed, it is good for bedroom playing. My amp is SS anyway so it doesn't really matter to me, I guess, though.

Thanks for the hard work.

[nickbungus]

I've updated the images.  The sizes are 52mm x 94.5mm

I had a few places where I had holes for a ceramic but used a mylar and the other way round.  These are now fixed.  Also, the schematic has polarised 220n's but I used some ceramic non-polars for these.

[nickbungus]

I dont know how genuine these are as they were stolen from another forum but heres a list of mods:

Diezel mod:

C35 : remove
C34 .047uF
C25 : remove
these three mods remove harsh

C42 1uf
D3 DEL
D4 1n4001
------ make the sound more dynamic and full
C36 .1uf----- EQ more usefull

Boogie/Bogner mod:

C35 a enlever
C34 .047uF
C36 1uF
D3 led
D4 1n4001

EN PLUS:
R46 increase values, more pre-distortion + mids
R41 reduce value you obtain more distortion (470ohms to start)


Mods don't have the same sound of diezel amp or Bogner amp, but it can be better tant the stock sound.



Keeley mod:

C20 .22uf
c42 .1uf
c37 , c39 , c17 , c11 1uf
c8 .22uf
c9 .1uf
c20 .22uf
d3 , d4 LED

I'm going to give the Keeley one a shot.

[ElectricDruid]

I'd like these sort of mod suggestions much more if they came with some more detail about *what they actually do*.
No criticism of you intended, nickbungus. I know how it goes, and we look for clues wherever we can find them. Me too. But I wish the people who came up with mod X or mod Y actually bothered to understand what it was their mod had altered and quantified it in some way.
What I'd like to see is stuff like "Change C46 from 330n to 470n to move the midrange peak down from 2KHz to 1.4KHz" or similar (I made that up - don't try it). But instead we mostly get touchy-feely stuff, like " change C46 to 470n to remove harsh top end". One person's "harsh top end" is another's "cutting solo tone". I'd rather have a few facts.

</grumpyoldman>

Tom

[nickbungus]

Sorry. It was a blind copy and paste job as is looking for what he mods are.   For the uneducated like me,  I usually find a YouTube video comparing the stock model against a modded one.

I do wish I understood more though and had the facts.

[nickbungus]

I etched my copper fill board and it was a bit tight with the gaps so heres a later version:

[swever]

I am going to perform a dark magic trick and resurrect this thread just to say a big thank you to Nick! I think more people should see this.

I almost shed a tear when I heard this amazing "djdjdj" for the first time since around 2003 when I bought the original. It was the first pedal I ever bought, also with my first self-earned money (I think I was still in high school).

Anyway, I've got mine up and running. For some reason my low pot does not work. It seems like it stays in it's neutral position, because there's just enough of it, haha. Let's see if I can find what's wrong once I am sober

[nickbungus]

You're more than welcome.  I love mine and still use it although not for gigging.  I use it in the house for those hair metal moments. 

[swever]

I'm not sure whether it's better to start a new debugging thread or not so I just post here. For some reason my LOW control does not seem to work properly. 

My LOW control does not seem to work correctly. At first it did not work at all, then I found a broken pcb track around c008 and fixed it. Now it seems that the control works as some sort of a mixture of gain and volume control (my wild guess is that it could be a way too low Q, but I am absolutely not sure).

When I started debugging, I noticed that C009 was missing in the redrawn schematic. However, it is present in the layout. I checked all the components that I believe to be the low freq control gyrator and all the values appear to be correct.


(I added the c009 to the drawing)

I am almost certain that it's some sort of silly mistake I made somewhere (as always), but I am clueless. Any suggestions please?

[nickbungus]

Chuggs spotted the missing cap.  I fixed it but didn't upload the amended schematic

[swever]

I am still struggling to get the LOW control working right. Could someone please suggest me something else to try before I go nuts and smash the board with a hammer, start running naked in the street ect?

[nickbungus]

Sorry, I would love to be able to help but I'm an idiot and I dont really understand electronics.

But if you want me to test anything on my working board I will gladly help.

[swever]

Thanks for your support, Nick! You've done a great goodness for the community already by making this thread happen!

It would be really helpful if you could measure the DC voltages at all pins of U01 and U04 IC's. Or, if you really don't mind, at all the IC's and transistors so that I don't molest you again later.

Talking about being an idiot and not understanding electronics, I am a damn expert at that stuff