Jordan - Gig Wah

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Rambozo96
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Post by Rambozo96 »

Bought a broken Jordan Gig Wah off the bay in hopes of repairing it and hopefully drawing up a schematic for it. As it stands it appears to use a rather odd (and probably one of the first) opamp (an MC1709C reportedly). Will report my findings when I get it on the bench. In the meantime I found the datasheet for said opamp, quite an unusual pinout!
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Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
Completed builds: Superfuzz’s, Mosrite Fuzzrite, various Tonebenders, some oddball Russian stuff, MXR Distortion II, modded various DOD pedals to true bypass, opamp Big Muff.
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Post by Rambozo96 »

Ok it arrived and I notice the following:
•Uses a 14 pin Motorola MC1709CL chip.
•Seeing how the 2 battery clips are wired I suspect that this is used two 9v batteries to achieve a bipolar 9vdc (like the Mutron III)

I provided a gutshot of mine, I seen another Gigwah with what appeared to be a 8 pin chip. Since I do not have this version the best I can do is try and trace this version with the 14 pin chip. Will report back when I uncover any new findings, a dual gang pot is also used.
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Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
Completed builds: Superfuzz’s, Mosrite Fuzzrite, various Tonebenders, some oddball Russian stuff, MXR Distortion II, modded various DOD pedals to true bypass, opamp Big Muff.
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Post by Rambozo96 »

Obviously my provided datasheet is incorrect as it shows a DIP8 package when mine is a DIP14. Had to purchase a Motorola IC datasheet book from 1973 in hopes my oddball chip is in it. Set me back a good $16 just to get info off the chip but I been wanting to document and dissect one of these for a while.

Manfred
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Post by Manfred »

I found the LM709 as a replacement for the MC1709CL, which shows the pinout for the 14 pin dual-inline package
LM709 Operational Amplifiers.pdf
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Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
Completed builds: Superfuzz’s, Mosrite Fuzzrite, various Tonebenders, some oddball Russian stuff, MXR Distortion II, modded various DOD pedals to true bypass, opamp Big Muff.
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Post by Rambozo96 »

Quite odd that in the 14 pin chip there’s a bunch of pins that appear to serve no purpose....odd. I thank you for digging that up for me. Will use this to progress in the tracing of the pedal.

Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
Completed builds: Superfuzz’s, Mosrite Fuzzrite, various Tonebenders, some oddball Russian stuff, MXR Distortion II, modded various DOD pedals to true bypass, opamp Big Muff.
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Post by Rambozo96 »

And looked at the traces of the pedal and it seems only pins 3, 4, 5, 6, 9, 10, 11, and 12 have traces that lead elsewhere. The unused pins are merely given a solder pad. I got a schematic halfway drawn up, I’ll triple check before giving it to the forum for public consumption, bad schematics are a common issue these days and I don’t wanna add to said problems. Thanks again Manfred!

Manfred
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Post by Manfred »

Hi Rambozo96,
do you have a shot of the solder side?

Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
Completed builds: Superfuzz’s, Mosrite Fuzzrite, various Tonebenders, some oddball Russian stuff, MXR Distortion II, modded various DOD pedals to true bypass, opamp Big Muff.
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Post by Rambozo96 »

I don’t at the moment but I can when I get home. Is that the best method of tracing a pedal? I just follow the traces and use my ohmmeter to confirm the connection between the components. As it stands the dual gang pot shaft is broken where it separated from the inside which may be the cause of the reported “random shriek” the pedal produces when you use the treadle. I don’t know where I’ll locate the pot for it. Seems like the top one is about 50k and the bottom 150k, I suspect one of them performs the volume pedal function.

Manfred
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Post by Manfred »

For tracking I scan the solder side and use the image as a rough PCB layout with the Sprint Layout 6.0 software.
With this software it is possible to insert this image in the background, so you can easily insert the components, pads and traces in the correct position.
With the integrated test function software the connected pads and traces can be highlighted for the clicked element.

Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
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Post by Rambozo96 »

Finally got around to it.
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Rambozo96
Posts: 41
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Post by Rambozo96 »

I’ll try to take a picture of the two 9v set up. On one clip the positive goes to the ring lug. Most of those chicklets are .1uf, one of the ceramics is 220,000 pf so .22uf basically. Hopefully in the enclosed pics I took clear enough shots of the chicklet and ceramic caps. Both electrolytics are 20uf.
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Manfred
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Post by Manfred »

I am currently working on a PCB clone, could you please fill in the component values.
JordanGigWahPCBComponents.jpg
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Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
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Post by Rambozo96 »

Working on that now! Thanks

Manfred
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Post by Manfred »

I added the connection points to the new component view, please also enter the targets of the wiring there and check the values already inserted,
JordanGigWahPCB_Layout.JPG
JordanGigWahPCB_ComponentSide.jpg
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Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
Completed builds: Superfuzz’s, Mosrite Fuzzrite, various Tonebenders, some oddball Russian stuff, MXR Distortion II, modded various DOD pedals to true bypass, opamp Big Muff.
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Post by Rambozo96 »

Here we go
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Rambozo96
Posts: 41
Joined: 08 Oct 2018, 00:01
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Post by Rambozo96 »

If any more questions let me know.
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Manfred
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Post by Manfred »

Here is the preliminary schematic in accordance with the layout and pictures.
The values of the potentiometers and the electrolytic capacitor which is connected to pin 10 of the operational amplifier are still missing.
JordanGigWahSchematic preliminary schematic.JPG
JordanGigWahLayout2.JPG
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