Installing a 3pdt switch into a vintage US Big Muff Pi

[decadentdesign]

Hello,

I'm new to the forum and relatively new to modding and building this stuff.  I have an older Big Muff and I can't seem to find any good instructions on how to replace the original switch (which was splintered into pieces) with a new 3pdt true bypass switch.  The confusing thing is, there were only three wires running into the original switch, and since it was in pieces I couldn't even perceive how they were connected.  Here's a pic of the innards...



Any help with this would be appreciated.  Once I get through this project I may think about other mods ~ any recommendations?  If this pedal has any real value I'd probably not try, but if this is a common enough pedal then why not?

Thanks!

[salocin]

http://www.singlecoil.com/docs/vintage_muff.pdf
Found at http://www.singlecoil.com/frmset.html

[decadentdesign]

 Thanks for the link though I actually already saw that... If youcompare the picture that I posted to the example you'll notice the three wires don't match up and if you look even closer the boards are differentt too! I would be guessing if I tried connecting wires based on that.  I need help for the version of the BM I have and not well versed in reading schematics...

[scott_v]

if you plan on using the 3pdt in that picture then you'll need some extra connections to be made or you can choose to not use a row in that switch turning that 3pdt into a dpdt type.

A 3pdt switch is used with an LED, i believe vintage US muffs did not have an LED???

if you going to add an LED you need to drill a hole and add an LED with a resistor in series to it...

I'm pretty sure these vintage muffs were NOT wired true-bypass at the time, but you can do it now with or without a LED.

you'll need to identify the lose connections, and you'll need more than 3...

the connections required are:

1. from the input jack (which i can see the loose wire in that photo)
2. from the output jack (which i can see the loose wire in that photo)
3. input from the circuit board
4. output from the circuit board (this maybe from lug 2 on the volume pot?)
5. universal ground (likely where that black wire from the battery clip is going to on the board, can't tell from the pic...)

need to find those board connections & ground, i see one wire from the board its hard to tell what it is, you almost have to flip the board and follow the circuit to determine where is what... plus ther eis that on/off switch? between the jacks i forget how this is connected on these older muffs.

go to the "DIY FAQ" section of this site and lookup switching and you'll find diagrams on how to do some of this... plus maybe someone from the Electro-Harmonix forum thats well versed around the many versions of these Big Muff can help identify those wiring connections.

[decadentdesign]

Wow, this is turning out to be way more complicated than I had expected... Now I'm thinking true bypass is not the way to go...  Thanks for the info though. If I knew a little more about this stuff maybe it wouldn't seem so intimidating...

[Brymus]

Look in the gallery(do a search) there is an excellent PDF on converting the BMP to true bypass with a 3pdt.
There are two more you might want as well,one on the history another on modding the factory circuit boards.

[petemoore]

  I didn't hear about input needs grounded, in my BMP it isn't.
 So
 Input jack to left, output jack to right, [middle row across has open lug still at switch's center.
 Jumper across from L-top to R-top, your bypass should work through the jumper side of the switch [ie you may have to switch it once.
 Since you want input to circuit input when you hit the switch, Left Bottom to circuit input wire, R-bottom to circuit output wire [you can see how the circuit is like the jumper, signal goes either through the jumper 'around' through the top lugs of the switch or the circuit through the ''bottom'' outside lugs.
 The LED wiring goes in the middle and is separate from [except that it 'borrows the power supply'] from the audio circuit power supply.
 So effect and bypass work, then it's just put the Led circuit through the remaining middle and bottom lugs of the switch, so when the switch is 'up' using picture as model, the LED circuit is opened.
  If nonsense^, start by using the DMM to Left/middle lug, it should 'beep' through the top left lug, or the bottom left lug, depending on the switch mode [hit the switch].
  The middle column and the right column do the exact same thing, separately, and simultaneously...think three switches side by side, each has 3 lugs for Throw
Pole
Throw

[zombiwoof]

 I didn't hear about input needs grounded, in my BMP it isn't.
 So
 Input jack to left, output jack to right, [middle row across has open lug still at switch's center.
 Jumper across from L-top to R-top, your bypass should work through the jumper side of the switch [ie you may have to switch it once.
 Since you want input to circuit input when you hit the switch, Left Bottom to circuit input wire, R-bottom to circuit output wire [you can see how the circuit is like the jumper, signal goes either through the jumper 'around' through the top lugs of the switch or the circuit through the ''bottom'' outside lugs.
 The LED wiring goes in the middle and is separate from [except that it 'borrows the power supply'] from the audio circuit power supply.
 So effect and bypass work, then it's just put the Led circuit through the remaining middle and bottom lugs of the switch, so when the switch is 'up' using picture as model, the LED circuit is opened.
  If nonsense^, start by using the DMM to Left/middle lug, it should 'beep' through the top left lug, or the bottom left lug, depending on the switch mode [hit the switch].
  The middle column and the right column do the exact same thing, separately, and simultaneously...think three switches side by side, each has 3 lugs for Throw
Pole
Throw

Using the wiring true bypass scheme that grounds the input of the board in bypass is supposed to help with popping issues.  It's not necessary to ground the input, but many think that is a superior method because it can help with the popping.

Al

[petemoore]

  Being wired as described, knowing what grounded input is like isn't happnening here, ie, the BMP works...it has enough pop that I had to check it, ie enough that it does pop but small enough that I couldn't remember registering or thinking about it before.
  So, the pulldowns are fine with this one, and I still wonder if a last little bit of pop can be reduced by input grounding, which of course is effective for eliminating bleed-through or pinning self-oscillation to a ground point.
 

[decadentdesign]

Brymus - Thanks for the info, but...  I'm pretty sure that the pdf you are talking about is the same one that someone else posted and in that, if you look at the board that they modded, it's different.  The wiring is just different.  Maybe if I understood this stuff a little better (and I think I'm starting to) I'd be able to take that info and apply it to my version of the muff.  But right now I was just hoping to find instructions for the exact version that I have.  I suppose I didn't realize how many variations there were and I'm really wondering which version it is that I have now...

Petemoore - I think I'm following what you are suggesting.  I'm going to print that out and see if it makes sense when I get inside the BMP again.  Thanks for the info!  I might have to get back to you all on the ground since that part is still evading me, but right now it sounds like it's not required... 

Wish me luck and I'll let you know how it goes...

[petemoore]

  Either method bypasses.
  The input ground method is harder to explain.
  The orientation of the switch in your picture made it easier to explain the 'Left is left / right is right'' of the input/output, it's a pretty straightforeward top/bottom deal.
  The grounded input method took a while to understand when looking at it, then when I decided to try one I had to stare at it again and analyze it before the 2 paths for bypass/effect became clear.

[zombiwoof]

Here's a link to GGG's   "Bypass Switching Options", scroll down to the ones for a 3PDT switch and pick the option you want (battery only, with LED, etc.), and open the link.  It will give you diagrams for the different types.  I would assume you want true bypass, but I'm not sure you want the LED option, or if your pedal is negative or positive ground.  I like the wiring with the input grounded, but that's up to you.  Check it out, and see if it helps:

http://www.generalguitargadgets.com/content/view/33/27/

Al

[decadentdesign]

Ok, this is probably going to sound like a stupid question, but...  how come, on the input side, the only connections to the jack appear to be to the same point (i.e. the tip).  there are two wires soldered to the same point but nothing to the other contact.  Is it possible that the case itself is actually conducting a signal from some point to another? 

[dune2k]

Ok, this is probably going to sound like a stupid question, but...  how come, on the input side, the only connections to the jack appear to be to the same point (i.e. the tip).  there are two wires soldered to the same point but nothing to the other contact.  Is it possible that the case itself is actually conducting a signal from some point to another? 

The case is grounded and since both jacks are connected to it they are too.
You should use a wire to connect them though, since they might come loose or dirty or whatever and the result would be the effect not working properly.

[decadentdesign]

So yeah, this is definitely more than I was expecting...  Guess I was assuming it would be more like paint by colors, matching colors, etc. but this is a bigger project than I had planned.  That said, I'm still working through it.  Knowing that the ground is running through the case helps for sure and sort of explains the lack of one of the wires I expected to see.  I'm going to go and look at everything I have and see if it's making more sense yet and get back to you all. 

I appreciate all your help and input BTW!

Oh yeah, and would I be assuming correctly that my version of BMP is the Ram's Head?  The pot's are in a row and it has the head graphic in the bottom corner with the BMP in red...

[decadentdesign]

You know...  Everytime I think I'm about ready to start soldering/desoldering I start thinking about it more and end up with more questions...

Looking at the input jack the only wires are coming from the 'tip' lug or connection and nothing is apparently contacting the sleeve?  Does this make sense? both the input wire (to the board) and the wire that ran into the switch are attached to the same ring that contacts the tip.  On the output jack though it appears that output wire from the board runs to the sleeve and one of the wires from the original switch runs to the tip (this I'm thinking is the bypass).  The third wire that was attached to the original switch runs to the volume pot (middle connection).

It just seems odd to me that the main input and output wires from the board would reverse from 'tip' connection on the input to the 'sleeve' connection on the output.  Also, it then seems that there is no signal transfer for the input 'sleeve' which doesn't sound right.



Maybe the sleeve is actually running a contact through the case?  I guess I'm going to have to take of one of the jacks to better perceive what's connecting to what...

If I just start soldering things, what are the chances that I'll blow something or ruin some of the components in this pedal?

[dune2k]

As I said the ground connection between the 2 jacks is mad through the enclosure. Since EHX used a non true bypass method on the BMP the input is connected to the circuit all the time and they basically just switch in/out the output.
the second wire on the output jack is there to connect circuit ground with the ground of the output jack (and the case).
the wire from the pot is basically the output of the circuit.

[decadentdesign]

As I said the ground connection between the 2 jacks is mad through the enclosure. Since EHX used a non true bypass method on the BMP the input is connected to the circuit all the time and they basically just switch in/out the output.
the second wire on the output jack is there to connect circuit ground with the ground of the output jack (and the case).
the wire from the pot is basically the output of the circuit.

Yeah, I guess I get that now...  For some reason I was mixing up which was ground and didn't realize that the sleeve is the ground.  Using the multimeter and a bit more research suddenly made that clear.

But what I still don't understand is the input wire is wired from the tip (positive,right?) but output is to the sleeve/ground.  On the otherhand, the output for the bypass runs to the positive.  Is this normal?

Thanks for all your help!!!

[decadentdesign]

I did it!  What was confusing me I think was the one wire running to the ground on the output side.  I finally realized that was just a ground running to the board (since there doesn't seem to be one anywhere else).  I did go ahead and add a wire from the ground in to the ground out and replaced and added wires that I was working with.  Here's the finished project...



It sounds great ad I didn't notice any clicking. when I hit the switch on and off.  I'm very pleased.  Thanks for all the help and advice (and patience) to those who have helped ~ much appreciated!

A follow up question...  Is it me, or do some people over complicate the wiring of the 3pdt switches for little or no reason?

Past that, now I'm thinking about adding a power adapter plug and an led.  Is that going to hurt the value of this pedal?  The case is actually rather worn so I'm guessing this wouldn't be an ideal unit for sale, but all the same, I'm not sure how far I should go before leaving well enough alone.  Being able to run this with an adapter would be really helpful and the led would just be convenient.  If I go that far I'll probably replace the battery cable and I'm thinking that maybe I should go ahead and just disconnect the on off switch in the back that doesn't really seem to be all that necessary... Thoughts?

Thanks again for the input and help!

[tiges_ tendres]

I
A follow up question...  Is it me, or do some people over complicate the wiring of the 3pdt switches for little or no reason?

No, there is a reason.  Often the more complicated wiring on 3pdts are so that the input of the effect is grounded when the effect is switched off.  This is especially useful in high gain pedals as it can help to quell oscillations that can sometimes occur if the input is left floating.