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Notes on Boss OS-2 schematic
----------------------------
2nd edition: 7/12/2002
Some errors are corrected; you'll find that the new schematic has some components that have a curved line drawn around them and a triangle with a "2". These are components that were wrongly named and/or valued up until this edition (Probably by copy/paste- and typing mistakes).
Changes:
OLD -> NEW
---------------------------
* R48/100k -> R17-100R
* C13/47n -> C29/10n
* R50/56k -> R43/1M
* C32 -> C31
* C15 -> C14
* C20/10n -> 100n
* R29/4k1 -> 4M1
* C8/20p -> 820p
I'm really very sorry if any of you have encountered problems due to my typo's. If there are any more comments feel free to send me an e-mail.
===============================================
1st edition: 30/12/2001
Text on my circuit board contains error !!!:
2 transistors are labeled Q6! I renamed the JFET
to Q8 (as this number wasn't used). This error
might be revised on newer units so watch out:
you might need to swap names of Q6 and Q8 in the
schematic if you have newer unit !! You can tell the
difference by the numbers on them (see below)
I don't know which one of the Q6's those guys at
Roland would rename in a revision.
Additional info on components:
------------------------------
IC1: Mitsubishi M5218AL dual opamp 8-pin SIL
Pin4=GND
Pin8=9V
IC2: JRC 14580 dual opamp 8-pin DIL
Pin4=GND
Pin8=9V
VR2=20kG (A=lin;B=log; but wtf is G???)
VR3=270k Stereo pot (no text on pot; value measured with DMM. I also don't know if it's lin or log, but I guess that doesn't really matter since "drive" doesn't count in numbers, right? I'm only kidding. it will of course effect your level of fine-tuning)
All VR's and C35 are mounted on a separate "VR-BOARD" connected to the main PCB with a 13wire Flat-Cable. These 13 wires are labeled 4~16.Other cables:
1: Input (grey)
2: PCB GND to input-jack (brown)
3: Adaptor GND to input-jack (black)
.
.
. (4-16 are in flat-cable; see above)
.
.
17: Battery +9V (red)
18: Cable to Footswitch (purple)
19: Output (white)
20: LED anode (orange)
21: LED kathode (green)
Output jack is grounded to pedal body; NOT to PCB.
Connection from PCB ground to body is through input-jack-ring (I wouldn't risk it. If you want to build this, i'd recommend connecting the output-jack-ring to PCB
as well)
All resistors: 0.25Watts 5%
All "1 Megaohm" resistors 10% (?)
D1: 1N4004
D5: 5.6V Zener
D11:Red 3mm LED
All other diodes are ordinary switching diodes, I guess. I tested one and it has a regular voltage drop of 0.65 V.
Q1,Q7,Q6*: 2SK118Y (N-ch. JFET)
Q4: 2SK184GR (N-ch. JFET)
Q2,Q3,Q5: 2SC3378GR (NPN) (good replacement: 2SC2240BL)
Q8*,Q9: 2SC2458GR (NPN) (good replacement: 2SC2240GR)
Difference between 2SC2240's is in hFE-values
(BL:hFE=350~700 ; GR:hFE=200~400).
(Q6*, Q8*, see top of text.)
In schematic, the power supply is in the top left corner. The 9V point (above D1) is used to feed the OP-AMPS and transistors. The feed of the
circuitry is (mostly) done with 4.5V (Vcc/2) derived from the connection between R8 and R9. So: All the arrows marked "9V" or "Vcc/2" in the schematic are in fact connected to their match in the upper left corner.