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Hi,
the Maxon CP101 Compressor is an higly regarded opto-compressor. If someone is interested in analysing the circuit here it the schematic and the PCB layout.

This Schematic is for the vintage red Maxon CP101 Compressor.
The new black Maxon CP101 Compressor has the same circuit but some added features, it has a input buffer, fet switching if I recall and uses 4558 instead of 741.

Hi there,

I was just wondering if anyone knows how to mod the attack of this pedal.

On the Maxon website there is advertised a " Subtle Squash Mod ". ( as well as a super squash mod ).

can anyone figure out what this would involve ?

Thanks in advance.

Borderline wrote:Hi there,

I was just wondering if anyone knows how to mod the attack of this pedal.

On the Maxon website there is advertised a " Subtle Squash Mod ". ( as well as a super squash mod ).

can anyone figure out what this would involve ?

Thanks in advance.

I have no ideia,
also I dont know why do they have that in their website?

Are they offering those mods for that pedal?

The strange thing is , theres no way of contacting Maxon themselves. you have to go through godlyke the distributer. I remember asking before when only the subtle squash was advertised. They replied that they couldant contact anyone who knew how to do the mods anymore.

i went back on the site recently and they have now added super squash mod - so i dont know whats changed. Ive shot them a mail but not very hopeful for an answer to be honest.

it would be great to be able to add an attack knob.

I've contacted Maxon directly in the past using this email:

maxon5@maxon.co.jp

There's also this one, but I got no luck:

sales@maxon.jp

Came here looking for a schematic of a simple optical compressor and found only broken links. Best I could find on the web was a blurry lo-res thumbnail by Yamazaki. So I've redrawn the schematic starting with the blurry thumbnail and using part values from Storyboardist layout. This schematic is the vintage red version with features added from Storyboardist's layout; input pulldown R1, reverse polarity protection D1, and power filtering C9. I also added component numbering.

G.Bisson wrote: ↑16 Sep 2021, 14:55 Came here looking for a schematic of a simple optical compressor and found only broken links. Best I could find on the web was a blurry lo-res thumbnail by Yamazaki. So I've redrawn the schematic starting with the blurry thumbnail and using part values from Storyboardist layout. This schematic is the vintage red version with features added from Storyboardist's layout; input pulldown R1, reverse polarity protection D1, and power filtering C9. I also added component numbering.
Maxon_CP101_schem_GBisson.png

Ldr's anode should be connected to v+, not ground

plush wrote: ↑16 Sep 2021, 16:18

G.Bisson wrote: ↑16 Sep 2021, 14:55 Came here looking for a schematic of a simple optical compressor and found only broken links. Best I could find on the web was a blurry lo-res thumbnail by Yamazaki. So I've redrawn the schematic starting with the blurry thumbnail and using part values from Storyboardist layout. This schematic is the vintage red version with features added from Storyboardist's layout; input pulldown R1, reverse polarity protection D1, and power filtering C9. I also added component numbering.
Maxon_CP101_schem_GBisson.png

Ldr's anode should be connected to v+, not ground

Fixed, thanks

It's likely to be the same board as the old Orange Ibanez Compressor, This one is a later version and has an LED.

viewtopic.php?f=19&t=1880

pics, pcb CO102A

https://www.tonehome.de/ibanez/narrow-b ... ompressor/


The version prior to that had no LED (and no power jack). About 1977.
It had the trimpot loaded and transistors were 2SC828Q. PCB marked MP-CO102A.
Pic attached.

There was an earlier version which didn't have the trimpot.
Off-hand the trimpot wasn't even on the board and the board was CO102 without the A.
These might go back to 1974/1975.

And yes these units had 100 ohm emitter resistors and no diodes on the two rectifier transistor.

Bought a modern 2010's black label version to dissect. I traced the entire circuit and drafted this schematic:
Few extra notes:
All capacitors 1uF and above are electrolytic type. C9 is a bi-polar electrolytic. All 1uF caps are 50v. All 10uF & 100uF caps are 16v. C4 is 10v. C18 is 6.3v.
I was unable to read any markings on D1 and guessing it's a 1N4001, 1N5817, or similar.
Diodes D2 & D3 appear to be small signal diodes similar to 1N914. They have a very short glass drop casing, shorter than a typical 1N914.
I've included most of the jumpers (JP#) on the schematic, except JP1 and JP9 are not shown. They are both part of the Vb pathway.

The control of the gates of Q1 and Q2 is missing in the schematic, there is no connection to the circuit around the toggle switch.

Manfred wrote: ↑30 Sep 2021, 02:42 The control of the gates of Q1 and Q2 is missing in the schematic, there is no connection to the circuit around the toggle switch.

Opened up the pedal again to confirm there's a trace between C14 & R29 that's faintly visible in the photo. Schematic has been updated.

This is the link for the optocoupler:

https://www.datasheetarchive.com/pdf/do ... P873G35687

check the connections around R12 and TR3 collector. They don't functionally make sense ( in my mind at least).

bmxguitarsbmx wrote: ↑30 Sep 2021, 17:13 check the connections around R12 and TR3 collector. They don't functionally make sense ( in my mind at least).

Misread my own fat marker tracings! Updated the schematic again. Detector circuit now looks identical to the older pedal version.
Thanks to all the extra eyes checking this.

I traced the entire circuit and drafted this schematic:

For the 2010 version the Trimpot is 500 ohm like the other versions.
(The marking is 501 not 105.)

george giblet wrote: ↑01 Oct 2021, 05:11

I traced the entire circuit and drafted this schematic:

For the 2010 version the Trimpot is 500 ohm like the other versions.
(The marking is 501 not 105.)

Fixed. Schematic has been updated.