Boss - OD-3 Overdrive [schematic]

[masajinobe]

For a long time I've wanted to do a re-trace of the Boss OD-3 OverDrive.
20 years have past since Luja/Axiom Drift posted his tracing.

The parts not on the Luja schematic are the footswitch flip-flop, power supply,
and also an addtional buffer in bypass path (that's where wampler's C18 mod comes in.)

I started tracing and found some errors in the the power supply section on the Luja schematic.
I just about got to the end after resolving a lot of part designators from pics and was
stuck on the voltage of the zener D13 as there were no clear pics. I could see "6B" or 68 on
one of the pics. Was it 5.6V or 6.8V? whatever the case it was clear is the power rails
for the overdrive section are somewhat lower than the 9V on the Luja schematic.

To cut the story short, I was hunting down pics trying to get a pic showing D13
and I found a Japanese blog with a very accurate tracing.
The tracing correctly shows all the power supply details and also has
correct part designators matching the PCB. The guy did a great job.

So here it is:

boss_od3_schematic - kanengomibako_dec_2021.png
boss_od3_overlay - kanengomibako_dec_2021.jpg


Boss OD-3 OverDrive schematic
kanengomibako
Dec. 2021

Boss OD3 Tracing, 1998 model
https://drugscore.blog.fc2.com/blog-entry-279.html
https://blog-imgs-132-origin.fc2.com/d/ ... ematic.png
https://blog-imgs-132-origin.fc2.com/d/ ... _2od3B.jpg

Additional info:
C24, C33 are tantalums
C17 located on Level/Tone pot board

Variants:
2017 Model:
- R3, R5 10k
(- it's possible the R3, R5 change also implies different IDSS category JFET switches.)
- C1 47n
- C25 100uF
- D13 larger package, black

Wires:
1 V footswitch
2 GY footswitch gnd
3 O LED+
4 GN LED-
5 W Output
6 BU 0V in (to input socket switch)
7 R +9V (to battery)
8 BR Input
9 GR GND (from input socket)
10,11,12 Level pot, Tone pot board
13,14 Drive pot board

I thought everyone already knew about his blog... there is also BD-2 SMD (& WAZA), but no OD-3 SMD.

[nooneknows]

So here it is:

boss_od3_schematic - kanengomibako_dec_2021.png

Hi,
after 11 years I come back to this thread to share the only really useful mod I've found in this pedal, but, well, it works to tame the bass, my only complain about this pedal: decrease C13.

Put a 22n or even a 18n in place of that 33n, that's enough. The characteristics of the distortion remains the same, it's just the output bass content being modified.

bye

[m4268588]

It looks good

[nooneknows]

I was expecting a bigger graph difference, anyway, it's clearly audible