Old Muff Revisited

[Phend]

Hello,
Way back, when I first became a member of this forum I was trouble shooting a 1970's version of a EHX Muff Fuzz.
Back then, after years of it sitting in a box I plugged it in. 
Did not seem to do much. A little but not any Fuzz.
I did find that R5 was 27K and not 2K7. (as many "Neg Gnd" schematics show)
I believe it is a manufacturing mistake in this particular effect, maybe even making it "rare".
But being that it is in a difficult place to remove I have left it alone.
I do not want to mess with this vintage effect any more than I have by removing and putting back the original transistors.
They too were also difficult to remove.
I have learned a bit since then.
Using the theory of constrictor parallelism I can make the 27K into a 2K7 with a 3K in //.
I have tried this (without solder) and it makes a huge difference.
One problem is that I cannot find any schematic of this particular Muff Fuzz.
It used BC239 transistors and has a Pos Ground. NPN with a pos gnd ??
The voltage readings are odd, Q1  C 6.8  B 8.0  E 8.6  Q2  C 4.0  B 6.8  E 7.5
Those are with the 3K possible modification.
BIG Question, should I solder in the 3K in parallel with the 27K and make the thing work Better ?
OR leave it alone because it is a vintage effect in somewhat working order ?
See Pics (note the 27K) and and circuit (I have drawn) I can't find anything like it on the web.
Thanks for any input !

[antonis]

I think you've messed up with supply polarity and various GNDs..

[Phend]

Thanks antonis. ...
The battery has always had the positive lead to ground.
The schematic is drawn same as the components are soldered together.
It is different from those when you search Muff Fuzz.
Note R1 and R2 are not directly connected.
Note the elec. cap, Plus is to ground.
Maybe this was made on Monday.

[antonis]

I also note the way Volume pot and diode pair are "grounded"..

[Fancy Lime]

This is quite curious. 1978 was when Big Muffs were in the opamp phase. I always assumed that this was also when the Muff Fuzz was switched from the BJT to the opamp version. I don't really know, though. Also, if the transistors are indeed NPN, I am very surprised that this thing works at all, no matter if R5 is 27k or 2k7. Could the transistors be mislabeled? Could they be different transistors by the same name? A lot of bizarre $#!+ happened back in the early days. More like early 60s than late 70s but maybe someone found an old box of odd transistors. Or is it possible that the enclosure is from an opamp Muff Fuzz and someone decided they'd rather have a transistor version so they gutted it and filled it with whatever is in there now?

Sorry, no answers, just questions...
Andy

[Mark Hammer]

I had one of those little spider-web monstrosities, with the components connected to each other "in air".  I still have the box (which houses an AMZ MosFet booster nowadays), and the components got repurposed for something else.  I have a Neo Muff that I modded to have variable gain and a treble cut.

That drawing is just plain wrong.  Because of how the components are connected to each other, it is difficult to know if the thing had been modified or improperly "repaired" unless one was the original owner.  Consult the drawing over at GGG to see it done right.  The Muff Fuzz is a silicon Fuzz Face circuit, set for modest gain, and supplemented with clipping diodes on the output.  The EHX Double Muff is two of them cascadable, in the same enclosure.

[Phend]

Yes, nuts, the transistors are BC239 and BC239c.
I am the original owner with sales slip and box. 1978.
I made no modifications. The schematic is what is there.
The case of the pot has the elec cap, diodes and + battery soldered to it.
And it works well with the 3K // mod if done.

[PRR]

...It used BC239 transistors and has a Pos Ground. NPN with a pos gnd ??

It's possible. Your hand-drawn schematic would work. It is strange, but Mike had access to strange wacky-weed in those days. I don't know why he would do that, and maybe he doesn't either.

[Fancy Lime]

It may pass signal, but it wouldn't be doing at all what a muff fuzz normally does. It would work as a (probably) mis-biased buffer with clipping diodes, if I'm not mistaken. Am I mistaken?

What I would do is put this thing back on the shelf for now, marvel at its oddness and put together a Muff Fuzz from scratch according to the "accepted" schematics out there. Then compare the sounds. These old plug-in boxes are historically interesting but their practicality in a modern setup is, uhm... a matter of debate. They make good conversation starters if you have them on a shelf in the living room, though.

Andy

[Mark Hammer]

The "accepted" schematic yields a pleasing grunt.  It's not intense enough to be described as a "fuzz", but it is clearly an overdriven tone.  A 10k C-taper pot in series with a 10uf cap to ground, in parallel with the 2k7 emitter resistor, provides for stock tone and higher-gain that gets you more of what people think of as "fuzz".

Alternatively, one can use the same trick as on Fuzz Faces and their derivatives.  Run a smallish (e.g., 220R) fixed resistor to a 5k linear or C-taper pot, whose other outside lug goes to ground.  The wiper goes to the aforementioned 10uf cap to ground.  Pot position dictates what the resistance is from emitter to cap, and consequently gain.

[Phend]

I added a 3K resistor in parallel with the 27K (mistake) stock resistor.
Been trying to fix this 1970's Muff for the last couple of years.
It should have been easy, in the end it was.
Back in the early 80's I made a double muff using the same circuit.
That circuit was the only one I had, ie copy the one in the "box". It worked well I remember.
Did I know what I was doing, NO.
RS was around so it was easy to get electronic stuff.
Fast forward 30 years, I made a few Muffs using GGG's schematic.
Here is a comparison of one I recently made and the ole 78.

[Phend]

Then compare the sounds. These old plug-in boxes are historically interesting but their practicality in a modern setup is, uhm... a matter of debate. They make good conversation starters if you have them on a shelf in the living room, though.

Agree, I can close the case of the Muffed up Fuzz. Display it under the TV in the living room. 
Take out battery first. Always take out the battery from unused effects.