MXR - Super Badass Variac Fuzz

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.

MXR - Super Badass Variac Fuzz

Postby dbalu » 05 Jan 2018, 01:56

Hello,
As I am an avid cloner myself, I thought that it's my time to give something to the DIY community. I got ahold of the effect mentioned in the title and I am providing some gut shots, also a list with components. Capacitor values on the list have "?" due to my lack of experience with SMD components. Where there is no indication on the list will be completed tomorrow then I'll get a magnifying glass. All other info from the list are markings on the components (mostly SMD).
Here are some links to the pictures. The final picture is the components list.
https://ibb.co/k3Rwuw
https://ibb.co/ctMMuw
https://ibb.co/i931uw
https://ibb.co/hWUruw
https://ibb.co/cMgh1b
https://ibb.co/g8bRSG
https://ibb.co/imkLnG
https://ibb.co/cDMt7G
https://ibb.co/irOHZw
https://ibb.co/eyf9gb
https://ibb.co/e34D7G
https://ibb.co/jKjVnG
https://ibb.co/fywMuw
https://ibb.co/jRmnZw
https://ibb.co/k7VQMb
https://ibb.co/gjOO7G
https://ibb.co/jF7uEw

For this message the author dbalu has received thanks: 3
dv8r601 (05 Jan 2018, 12:32), RnFR (06 Jan 2018, 07:54), twangcat (06 Jan 2018, 18:02)
dbalu
 
Posts: 3
Joined: 05 Jan 2018, 01:41
Has thanked: 0 time
Have thanks: 3 times

Re: MXR Super Badass Variac Fuzz

Postby modman » 05 Jan 2018, 19:06

Screenshot from 2018-01-05 18-52-39.png
You do not have the required permissions to view the files attached to this post.
User avatar
modman
a d m i n
 
Posts: 4346
Joined: 19 Jun 2007, 17:57
Has thanked: 3283 times
Have thanks: 611 times

Re: MXR Super Badass Variac Fuzz

Postby dbalu » 05 Jan 2018, 22:28

modman wrote:
Screenshot from 2018-01-05 18-52-39.png

If you want i can give you more detailed/Hi-Res pics of the circuit, these are made with my phone
dbalu
 
Posts: 3
Joined: 05 Jan 2018, 01:41
Has thanked: 0 time
Have thanks: 3 times

Re: MXR - Super Badass Variac Fuzz

Postby dbalu » 06 Jan 2018, 16:07

The rest of the values that were not included in the list
Q1-836
U1-K6NCD
D5,6&7-B2 INFINITY
U3-G114
Q6-GY G
Q8-JAM 6 sideways
Q3-1R6
D1,D2-AD
U2-K6NCD
Q2-GY G
Q7-1E6
Q5-GY G
D3-8F 6 sideways
Q4-1E6
D9-??BC
dbalu
 
Posts: 3
Joined: 05 Jan 2018, 01:41
Has thanked: 0 time
Have thanks: 3 times

Re: MXR - Super Badass Variac Fuzz

Postby 10goo » 12 Jan 2018, 18:53

Hello... I think I saw a YouTube video, where the guy explains how the "super badass" came about... It's a "Band of Gypsy" fuzz with a tone added....and then the "variac" circut added on...
You could start your search there...

Good luck
10goo
 
Posts: 2
Joined: 03 Apr 2014, 05:42
Has thanked: 0 time
Have thanks: 0 time

Re: MXR - Super Badass Variac Fuzz

Postby DanGibbs » 18 Sep 2019, 23:23

Hello All :)
I'm hoping that there's still some interest in decoding this pedal as I bought one that needed help off of Reverb last week and it doesn't pass audio at all when the effect is on/LED lit up.

I bought this as I like to buy broken pedals and fix them which I'm usually successful at except for a few new(er) Dunlop/MXR/WayHuge pedals that I/we cannot get schematics for.

I therefore earlier this week started a schematic "decode" of this pedal using EasyEDA and have the core effect-function of the pedal schematicized. I ran into a brick wall with regard to what I believe to be the "variac" portion of the pedal at U3 which is marked "|G114" - I did a five minute search on google and I found nothing like it which halts me in my tracks. I was earlier able to identify U1 marked K6NCD which is actually an MMDT3904, a dual 2n3904 package. I'm still trying to ID Q1 marked 9EB which measures as a PNP transistor albeit who knows which one. Some one before me also replaced Q8 and this replacement is marked 1AM - I don't know if this is actually the correct transistor or not as the pictures on this post aren't clear enough to read with regard to Q8.

I'm willing to schematicize the whole pedal if anyone can help figure out what all of the semiconductors are on the board.

In the photo with the pencil-written parts list, U4's part number is incorrect and should be TC7660SC which is the voltage-converter IC that I believe operates the 5-15VDC "variac".

I have an 94kB png image of the partial work-in-progress schematic but I don't know how to insert it here (why is it always so damned hard on a forum to just insert an image?!? -rantoff).

Dan Gibbs :)

For this message the author DanGibbs has received thanks:
ozzy666 (29 Sep 2019, 15:21)
DanGibbs
 
Posts: 2
Joined: 27 Jul 2018, 22:44
Has thanked: 0 time
Have thanks: 2 times

Re: MXR - Super Badass Variac Fuzz

Postby george giblet » 19 Sep 2019, 00:29

I believe to be the "variac" portion of the pedal at U3 which is marked "|G114" - I did a five minute search on google and I found nothing like it which halts me in my tracks.

U3 is some sort of regulator.

Go to the page 5 or 6 of this thread,
viewtopic.php?f=1&t=13121

So for the Variac, U3 pin 5 goes to R30 (41.2k), then R30 to U3 pin 4,
U3 pin 4 goes to R34 (34.0k), then R34 to ground.

From that I can see, the output voltage would be,

Vo = Vref * (R30 + R34) / R34

Where Vref is the reference voltage of the regulator referred to ground. I would expect Vref to be around 1.23 to 1.25V. However, it could be 1.14 following the number printed on the chip (as some regulators are marked like that). Suppose we go with 1.25V

Vo = 1.25 * (41.2 + 34.0) / 34.0 = 2.76V

That seems low but maybe the pedal is called "variac" because the voltage is reduced; as variac would do on an amp.

So keep going! It's only power rail. You will see the rest of the circuit make more sense once you know that.
Notice the output of U3 goes to a resistor R1 (10 ohm) then to maybe looks like big cap.
george giblet
Solder Soldier
 
Posts: 167
Joined: 30 Dec 2008, 18:27
Has thanked: 73 times
Have thanks: 90 times

Re: MXR - Super Badass Variac Fuzz

Postby george giblet » 19 Sep 2019, 00:33

However, it could be 1.14

Maybe even 11.4V. Don't worry about the details for now it might become clearer.

FWIW, in the other link I posted I've identified a lot of parts on that unit. You might be able to copy some of that info (the text in the thread had quite a few misidentified parts so watch out).
george giblet
Solder Soldier
 
Posts: 167
Joined: 30 Dec 2008, 18:27
Has thanked: 73 times
Have thanks: 90 times

Re: MXR - Super Badass Variac Fuzz

Postby DanGibbs » 26 Sep 2019, 02:05

Hello George Giblet and thanks for the info!

I've been working diligently in most of my spare time on the schematic and I think I have it all diagrammed. A crap-ton of stuff to figure out and trace for sure. I'm in the process currently of verifying traces between the actual PCB and my schematic after removing most of the through-hole components to make sure I haven't missed anything (I'm sure I have). I called and got the actual part numbers for all of the transistors and ICs last week but I shied away at that moment of asking for the diodes and SMT capacitors as I don't want to seem too greedy and burn that new bridge.

I'll definitely get back when I'm satisfied that the circuit is as correct as I can see it. The next debacle would be trying to re-arrange the schematic to where it's better than a ball of rewound yarn to where I can make sense out of the circuit sections (phwew whadda mess). I'll prolly upload it anyway once I verify the traces before I try to re-arrange.

Again, my goal here is to make a schematic to repair my non-op unit that I bought a few weeks ago. I'm not looking to clone it and I doubt it would really be worth the effort to most folks to clone it - just my opinion.

Dan :)

For this message the author DanGibbs has received thanks:
ozzy666 (29 Sep 2019, 15:25)
DanGibbs
 
Posts: 2
Joined: 27 Jul 2018, 22:44
Has thanked: 0 time
Have thanks: 2 times

Re: MXR - Super Badass Variac Fuzz

Postby george giblet » 29 Sep 2019, 03:41

I'm not looking to clone it and I doubt it would really be worth the effort to most folks to clone it - just my opinion.

Same here.
george giblet
Solder Soldier
 
Posts: 167
Joined: 30 Dec 2008, 18:27
Has thanked: 73 times
Have thanks: 90 times


Return to Modern Stompbox Effects (1975 - ...)

Who is online

Users browsing this forum: Google Feedfetcher and 19 guests