Help building the 70's Maestro MPF-1

[the-bna]

It's an old pedal designed originally by Bob Moog from what I understand. It was part of a series called the TFC-series (total foot control). And I want it - badly too. Unfortunately it's very rare, and I've been wanting to start building pedals for a while now. So yes, it will be my first build - even though it might be a little complicated for a first build. If it takes an extra effort so be it!

Okay so let me start out by posting schematics and a picture of the pedal.

Schematics: Here



1. First off. I've come to the conclusion that the numbers 1-12 in the middle of the bottom, and a little to the right of it are for a DP5T switch (a dual 5-way rotary switch, in-case naming them was only something I thought I knew how to). Can you confirm this?

2. (Answered) If it IS correct I'm looking for something called DP5T or 2P5T, correct?

3. (Answered) I want the shaft to be 1/4 inch to fit the most knobs, correct?

4. Have a look at this. http://www.surplussales.com/Switches/SWRoMisc-1.html Part number: (SWR) 172246-H1. It looks to have the right specs - except it's a make before break switch. Does this mean that for a very short while 2 pathways will be open at the same time? This is going to cause trouble isn't it?

5. (Answered) I have stumbled upon switches named 2P3-6T for example. The description said it was adjustable from 3 to 6 positions. Does this mean that you can lock it, so you can only turn it in 5 different positions? Cause I don't want an extra position, even if it does the same as the one before, or nothing at all. That would be sort of sloppy, and I don't want that in any way

6. (Answered) The schematics say I need a 10k S-Tapered pot for the "Height" control. What is S-taper?

7. (Answered) Do I need to worry about the quality of the pots and the rotary switch?

That's all the questions I have for now

[theehman]

So rare I have 2 of them plus the original box!
Unfortunately both need work and I have no time for personal projects at the moment.

Yes, it's a 2-pole, 5-position switch.  The adjustable ones will work fine.  There's a metal washer with a tab that locks it to however many positions you want.  You also want 1/4" shaft for most knobs.

According to a page at Angela Instruments ( http://www.angela.com/catalog/potentiometers/Alps_Pots.html ), S-taper is the same as linear taper.

As for the pot and switch quality, if you're going to move them with your foot, I'd use some heavy-duty ones.

[the-bna]

Thanks for the reply!

Yes, I also read about someone else who had the luck to find two of these in a music store, he wrote the might even have one left. As I live in Denmark the chances of finding something like that are extra low. I've also been watching ebay, but nothing has come up

Is there any way to tell if they're heavy duty? Should I be looking for a closed/packaged one as opposed to an open one?

Btw, I know this is asking a LOT, but could you possible take some gut shots of it? 

[theehman]

Thanks for the reply!

Yes, I also read about someone else who had the luck to find two of these in a music store, he wrote the might even have one left. As I live in Denmark the chances of finding something like that are extra low. I've also been watching ebay, but nothing has come up

Is there any way to tell if they're heavy duty? Should I be looking for a closed/packaged one as opposed to an open one?

Btw, I know this is asking a LOT, but could you possible take some gut shots of it? 

As long as there's little space for the knobs to move around you could probably get by on standard units.  The sealed units are nice because they keep dirt out however the open frame switch is a bit more robust than the enclosed (which is usually all plastic).

I'll see if I can get some gut shots to you.  Remind in a few days if I don't post them.

[the-bna]

Thanks a lot, sounds great! Thanks for the advice on sealed vs. open too.

About that make-before-break thing, do you think I should avoid that and get the standard break-before-make type?

[gigimarga]

What type of effect is this MPF?
How it sounds like?

[theehman]

What type of effect is this MPF?
How it sounds like?

It's a foot-controlled parametric filter.
Demo vid here: http://www.youtube.com/watch?v=w4Qzptnrjgc

[nelson]

Is this the QOTSA pedal?

[the-bna]

Is this the QOTSA pedal?

Yeah it is

[the-bna]

About S-Taper pots
It's true that S-taper pots are like linear pots - almost. Take a look at this:

Just to add to this... Most of the commercially produced TX pots have been designed so that they get they "full" 5K ohm range in the 60 (or so) degrees of rotation, this maximises the voltage change giving you the greatest range of values from the A/D conversion.

Right. Those are called S taper pots. They're also used in joysticks for computers and video games.

Any idea where to find these?

[gigimarga]

Wow...it sounds interesting...thx a lot theehman!

[nelson]

Cool, I might do a PCB for this - it looks like fun.

Some nice mods possible with this circuit too.

[MikeH]

A friend of a friend tried to get me to drill a hole in one of these and install a 9v jack.  I told him no f*ing way. 

[theehman]

A friend of a friend tried to get me to drill a hole in one of these and install a 9v jack.  I told him no f*ing way. 

Why not?

[the-bna]

A friend of a friend tried to get me to drill a hole in one of these and install a 9v jack.  I told him no f*ing way. 

Why not?

Dont get that either It's a pain having to change batteries all the time

[theehman]

Circuit board shot as requested (IC on right is missing):

[the-bna]

Thanks! Much appreciated

[gigimarga]

Anyone made a PCB for this in the meantime?

[fuzzo]

yeah, that could be really cool  ! (A guy of Freestompboxes.com has made a clone of this pedal)

[gigimarga]

Nobody?