LAL GM2 Green Monster (Lastgasp Art Laboratories)  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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Gila_Crisis
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Post by Gila_Crisis »

I recently got a LAL Green Monster, a super rare fuzz and long discontinued pedal by LAL.
Since I opened it to clean it a bit, I decided to take also some gut pictures.

Some notes to the pictures:
True bypass 3PDT footswitch
Pots: Vol 10kB, Sens1 10kB, Sens2 10kB, Sens3 50kB
Wiring: Green GND, Yellow OUT, White IN, Red +9VDC

Opamps are both UA741CP, and there are only 2 components which maybe are a bit tricky to track.
These look like 2 diodes: the black one in the middle of the board (I guess is a 1N400x for 9VDC polarity protection?), and the second is a black-yellow one (marked 4Z and something else I wasn't able to read: zener for LED power?).
The other diodes look like normal 1n4148 or 1n914 (clipping diodes I suppose).
Capacitors are marked 103, 104 and 56.

The RED +9VDC wire goes to one pins of the 3PDT switch and from there to the +9VDC power plug! That means when the pedal is bypassed (OFF) the power is killed on the whole circuit!

Enjoy and have fun with the tracing!

Official LAL website: https://lalweb.com/gm2/gm2-e.html
790FEC8C-52C3-438B-A272-1517C171A8BF.jpeg
Attachments
P1000798_Fotor.jpg
P1000801_Fotor.jpg
P1000803_Fotor.jpg
P1000806_Fotor.jpg
P1000809_Fotor.jpg
P1000817_Fotor.jpg
P1000831_Fotor.jpg
P1000832_Fotor.jpg
P1000833_Fotor.jpg
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karul
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Post by karul »

preliminary
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2.webp
1.webp

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ppluis0
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Post by ppluis0 »

fkj19072 wrote: 19 Apr 2022, 07:04 thanks for sharing
https://www.probestwriter.com
WOW !!! :shock:

There is a new ways to send unsuspecting readers to a commercial site:

Thanks for sharing...
I draw a layout...
Here is a veroboard for this schematic, etc. etc

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Post by Manfred »

I made a layout copy for tracking.
I found other positions of the potentiometer names.
I suspect that the D1 is a 1N4001 diode and D2 is a 5.1V Zener diode.
The clipping diodes looks like Zeners or Schottkies
Can you measure them with the multimeter.
Some multimeters have a measurement mode for diodes where the threshold voltage is displayed.
If no measurement is possible, it could be Zener diodes. In this case there should be an imprint with the Zener voltage.
LAL GM2 Green Monster schematic corrected.jpg
LAL GM2 Green Monster Layout.JPG
Ready-to-Print PDF-files:
LAL GM2 Green Monster Component Side.pdf
(10.22 KiB) Downloaded 81 times
LAL GM2 Green Monster Solder.pdf
(3.68 KiB) Downloaded 82 times
SprintLayout6.0-file´:
LAL GM2 Layout.zip
(12.18 KiB) Downloaded 66 times

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karul
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Post by karul »

My initial guess was that 50k pot is the one on the output too. But one photo (there was a link somewhere for bigger gallery with 40 photos and a note) shows 50k pot above the 10k resistor and two diodes. Also the position of the green and yellow wires is clearly visible.
LAL Green Monster:
True bypass 3PDT
Pots: Vol 50k, Sens 1-2-3 10k
Wiring: Green-GND, Yellow-OUT, White-IN, Red-9VDC
Opamps are 741
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1.webp
Last edited by karul on 21 Apr 2022, 19:51, edited 1 time in total.

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Post by karul »

Z4. visible marks for the diode. 4.1V, 4.3V, .... 4.x ?
J on the other one. It's for polarity protection so 1n400x would be fine.

link for the bigger gallery 140Mb zip file
https://mega.nz/file/Ct8ABApD#Zc2nYzH4e ... C6HB9e-eLo
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Post by Gila_Crisis »

Sorry for the mess with the pots.
I confirm Sens3 is 50kB all others (Vol, Sens1+2) are 10kB!!!


The "power diodes" diodes: the zener is the LED protection only, the other polarity power protection and looks like a 1N400x.

Note the wiring: when you bypass the pedal you also remove the electrical power from the whole circuit.
Ths said a normal true-bypass switch shall work as well.

The clipping diodes looks like 1N4148 or 1N914. These are used very often in LAL designs.
Last edited by Gila_Crisis on 30 Apr 2022, 06:00, edited 1 time in total.
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Post by Manfred »

Gila_Crisis wrote: 29 Apr 2022, 20:49 Sorry for the mess with the pots.
I confirm Sens3 is 50kB all others (Vol, Sens1+2) are 10kB!!!


The diodes: the zener is the LED protection only, the other power supply protection looks like a 1N400x.

Note the wiring: when you bypass the pedal you also remove the electrical power from the whole circuit.
Ths said a normal true-bypass switch shall work as well.

The clipping diodes looks like 1N4148 or 1N914. These are very often in LAL designs.
Here the corrected documents according your review.
LAL GM2 Green Monster schematic corrected 2.jpg
LAL GM2 Green Monster Layout corrected.jpg
Ready-to-print file:
LAL GM2 Green Monster Componets Side corrected.pdf
(10.51 KiB) Downloaded 80 times
Sprint Layout6.0 file:
LAL GM2 Layout corrected.zip
(12.28 KiB) Downloaded 77 times

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Post by Gila_Crisis »

Note that Deadend FX released a PCB for the Green Monster, called 'Zilla, with an additional switch for more gain and devastation!
https://www.deadendfx.com/product/zilla
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Post by digi2t »

Please note that the resistor that is 47R is actually 470K. If you look closely at the picture of the resistor, you can see that the black band has been deceptively hand painted. Not only are the edges not crisp, but you can see the yellow bleeding through.

Besides... there's no way you'll get enough gain out of it with a 47R, but 470K sounds just right. The DEFX board adds a toggle that switches between the original 470K and 4M7, which will totally flatten Tokyo. Again. :mrgreen:

And great big thanks and flying high five to gila for the chance to trace out these gems. Muchos gracias amigo! :applause:
No matter how many times I cut it, it`s STILL too short!

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Post by Manfred »

LAL GM2 Green Monster schematic corrected 3.jpg
LAL GM2 Layout corrected 3.jpg
Ready-to-print PDF-file:
LAL GM2 Components side corrected 3.pdf
(10.54 KiB) Downloaded 78 times
SprintLayout6.0- file:
LAL GM2 Layout corrected 3.zip
(12.37 KiB) Downloaded 76 times

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Post by karul »

digi2t wrote: 16 May 2022, 02:31 Please note that the resistor that is 47R is actually 470K. If you look closely at the picture of the resistor, you can see that the black band has been deceptively hand painted. Not only are the edges not crisp, but you can see the yellow bleeding through.
yep
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Post by Jarno »

That is very creative, and also a potential headache for someone looking to repair one of these products, unless a service manual is available (probably not). Also, it adds no value to the product, so yeah, idiotic.
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Post by digi2t »

Jarno wrote: 16 May 2022, 10:47 That is very creative, and also a potential headache for someone looking to repair one of these products, unless a service manual is available (probably not). Also, it adds no value to the product, so yeah, idiotic.
I prefer that to gooping. At least you can still get at it with a multimeter. Besides, it sort put my sleuthing skills to the test, and a decade plus of staring at schematics finally paid off. :lol:
No matter how many times I cut it, it`s STILL too short!

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Post by Gila_Crisis »

I've built a Green Monster clone following digi2t schematic and using his Deadend FX board: I compared it with the original LAL, and it totally nails the original GM!
Plus the Deadend FX has an additional switch to increase the gain in the IC1 stage, which is a nice addition to this noise maker.
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