Park - Auto Wah  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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analogguru
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Post by analogguru »

Interesting, I have never seen this before:

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

Somebody else ?

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MoreCowbell
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Post by MoreCowbell »

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


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Post by Professor SourTone »

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

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Ice-9
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Post by 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. :wink:
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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modman
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Post by modman »

Attachments
Park - Auto Wah
Park - Auto Wah
Park - Auto Wah
Park - Auto Wah
Park - Auto Wah
Park - Auto Wah
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Post by 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?
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Ice-9
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Post by Ice-9 »

Nocentelli wrote: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.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Ice-9
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Post by Ice-9 »

Pictures of top and bottom of PCB,
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Park autowah guts 2
Park autowah guts 2
Park autowah guts 1
Park autowah guts 1
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Ice-9
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Post by Ice-9 »

Sorry for the oversize pics, I have no idea why that happened ? right click and save for full picture.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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DanAmpora
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Post by 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 :lol:
Attachments
Park Auto Wah Schematic v1
Park Auto Wah Schematic v1

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Ice-9
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Post by 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.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Ice-9
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Post by Ice-9 »

The capacitor hidden under the bent over greenie cap is 1n
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Ice-9
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Post by 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. :thumbsup
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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Post by DanAmpora »

Thanks for the info, Ice-9. I'll breadboard this as soon as I can.
Attachments
Park Auto Wah Schematic v2 -- now with pot values!
Park Auto Wah Schematic v2 -- now with pot values!

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Post by 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)?
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by 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

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Manfred
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Post by Manfred »

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
(17.89 KiB) Downloaded 233 times
ParkAutoWahPCB_SolderSide2.pdf
(8.18 KiB) Downloaded 214 times
ParkAutoWahPCB_SolderSideMirrored2.pdf
(8.22 KiB) Downloaded 203 times
SprintLayout6 file:
ParkAutoWah_2.zip
(24.12 KiB) Downloaded 226 times

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Post by DanAmpora »

Manfred wrote:The polarity of C7 is wrong in the schematic drawing.
The indent (+) is toward the edge of the board.

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Post by Manfred »

DanAmpora wrote:
Manfred wrote: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.

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Post by DanAmpora »

In the process of trying to make a smaller layout with more modern components (think radial electros and EBCs :lol:) I somehow managed to redraw the schematic. Here's one for the archives:
Attachments
Park Auto Wah Schematic v3 -- oh hey the LFO makes sense now
Park Auto Wah Schematic v3 -- oh hey the LFO makes sense now

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