Park - Auto Wah [schematic]

[analogguru]

Interesting, I have never seen this before:

http://cgi.ebay.co.uk/Park-Auto-Wah-Mar ... dZViewItem

Somebody else ?

analogguru

[MoreCowbell]

Thats one Ive never seen either. It makes me wish I had a bunch of "expendable" money. It sounds cool from the description.


Link

[Professor SourTone]

Looks like a Mk1 Tonebender box, and the insides look pure Colorsound.

[Ice-9]

Sorry to raise such an old thread but I have just picked up one of these Park Auto-Wah pedals, it's in need of some TLC. I wondered if anyone had ever drawn out the schematic for this at all. There are not many components inside and it shouldn't take long to trace but if it has already been done it could save me 20 minutes drawing it out.

[modman]

I found this:
http://c-nelson.com/1960s-park-auto-wah/

[Nocentelli]

I had assumed it was going to be an envelope filter type "autowah"...

Is that four transistors? Perhaps a phase shift oscillator like schaller trem LFO coupled with a twin-t wah like the colorsound?

[Ice-9]

I had assumed it was going to be an envelope filter type "autowah"...

Is that four transistors? Perhaps a phase shift oscillator like schaller trem LFO coupled with a twin-t wah like the colorsound?

There are 5 transistors which are 2n3702 . I did make some pictures of both sides of the pcb , I will post them as soon as I get a chance.

[Ice-9]

Pictures of top and bottom of PCB,

[Ice-9]

Sorry for the oversize pics, I have no idea why that happened ? right click and save for full picture.

[DanAmpora]

Some pot values would be nice, and I'm not 100% sure about the pot wiring. I'd also like to confirm the values of the cap(?) hidden by the green cap (C2) and the other green cap under it (C4).

Happy holidays y'alls

[Ice-9]

Some pot values

SPEED = 47k Linear
TONE = 5K linear
DEPTH 5k linear

I will get back to you on the other values and wiring.

[Ice-9]

The capacitor hidden under the bent over greenie cap is 1n

[Ice-9]

Everything looks correct in your schematic DanAmpora, I just traced it out following my pictures and pcb along with your schematic. Pots are all correct as well as all comp values.

[modman]

Thanks for the info, Ice-9. I'll breadboard this as soon as I can.

[Nocentelli]

Thanks for all the effort on this one, an interesting little circuit. I'm going to have a play with breadboarding it: Might it work with NPNs and a "positive power" scheme (i.e. not positive ground)?

[Manfred]

The polarity of C7 is wrong in the schematic drawing.

I created a PCB-layout clone according to the PCB-shots.
The layout component names corresponds to the names in the schematic.

Ready to print documents:



SprintLayout6 file:
ready to print documents

[modman]

The EDIT-button does not work, for whatever reason.
Once more, therefore:
The resistor R11 did not appear in the layout.

ParkAutoWahLayout2.JPG

Ready to print documents:

ParkAutoWahPCB_ComponentSide2.pdf

ParkAutoWahPCB_SolderSide2.pdf

ParkAutoWahPCB_SolderSideMirrored2.pdf

SprintLayout6 file:

ParkAutoWah_2.zip

[DanAmpora]

The polarity of C7 is wrong in the schematic drawing.

The indent (+) is toward the edge of the board.

[Manfred]

The polarity of C7 is wrong in the schematic drawing.

The indent (+) is toward the edge of the board.

You are right, not your fault.
In my opinion the capacitor C7 is installed incorrectly,
because there is a negative DC voltage on the positive connection of it.
Maybe it will not be noted in practice, because the amount of the voltage is very low.

[DanAmpora]

In the process of trying to make a smaller layout with more modern components (think radial electros and EBCs ) I somehow managed to redraw the schematic. Here's one for the archives: