BOSS CS-1 v1 vs v2

[Rob Strand]

I'll open it up this weekend and report back.

Cool, be good to get the schem as close as possible.

[Ry]

I finally found mine on my 'repair/refurbish' pile.  It's really muffled and I need to work through it.

It's a V2, with Q10 and D5.  One difference is that I have D3 in mine, not a jumper.

As for your question about parts, the Diode reads 4.13v engaged.  I can take more readings if you'd like.  I didn't have time to pull it off the board and inspect the markings this morning.

The middle caps are 220pf and the lower are 470pf.

[Rob Strand]

I finally found mine on my 'repair/refurbish' pile.  It's really muffled and I need to work through it.

It is muffled in bypass mode?  Could be something simple like the connectors or output electrolytic cap those would affect both modes.   If it's only the compressor then maybe the pot or the two electros going to the treble switch.

It's a V2, with Q10 and D5.  One difference is that I have D3 in mine, not a jumper.

As for your question about parts, the Diode reads 4.13v engaged.  I can take more readings if you'd like.  I didn't have time to pull it off the board and inspect the markings this morning.

The middle caps are 220pf and the lower are 470pf.

Thanks a lot for checking those.  It's actually interesting that D3 is there.  I haven't seen small incremental changes like that in the same Boss pedal before.  I've only seen difference across different Boss pedals.

I'll have to measure the zener voltage on one of my Boss units to compare the voltage.  It looks like your zener is 4.7V.

So one thing that would be cool to check is if the resistor above Q10 (near wires 2 and 4) is 100 ohm or 1K.
I've only been able to work out that the 1K changed to 100R when the diode was removed.

----------------------------------------------------
Changes to Early Units

From mid 1979 to late 1980 there were circuit changes.
Across the board there were changes around the footswitch.
By Dec 1980 all changes are in place, which lines-up closely with the release
of the PH-1R.

I suspect devices before mid 1979 had the momentary check LED:
- SP-1, PH-1, OD-1, DS-1, CS-1, GE-6, TW-1, SG-1 (just)

Footswitch Circuit Changes: (intended to be in chronological order)
- Mods to make LED come on in Effects mode, instead of only being a
   momentary battery check while the footswitch is held down.
- Changes to circuit so LED is on in Effects mode.  LED current reduced.
  The LED is wired to the flip-flop or has its own transistor.
- (not sure of order, maybe later) Zener on LED changed from 4.7V to 5.1V.
- Change 1uF cap across footswitch changed to 10n.
- 2x470pF on input of Flip-Flop changed to 2x220pF
- (together?) Remove Flip-Flop emitter diode, and,
  Change footswitch series resistor from 1K to 100R.

Actual units are likely to have these small changes in spite of what
the official Boss schematics show.  Very early Boss schematics can
be different to later released schematics marked "First Edition".
----------------------------------------------------

[Ry]

The resistor above Q10 is 1k.

I have a TW-1 that I know is a later run, and at least one PH-1 (I think I have another that was waterlogged and beyond repair in a drawer somewhere).  I went through a period of collecting what appeared to be repairable Boss pedals.  I got quite a collection and only lost got a couple that I've not been able to fix easily.  Let me know if there's anything in these that you'd like me to check.

Thanks for the guidance on what to test for the muddy sound!  It's been a couple years since I had it hooked up, I'll give it a listen next!

[Ry]

Ok, it's actually the CS-2 that was sitting next to it that sounds ridiculously muffled when the effect is engaged and not the CS-1.  The CS-1 sounds as good as these things get!

[Rob Strand]

Diode reads 4.13v engaged.

I checked a couple of my units (1980 and 1988) which have 5.1V zeners.
The zener measured 4.3V to 4.7V depending if I plug in an unregulated supply
or regulated supply.   These are both old pedals that should use the unregulated
ACA supply which is about 12V.

External     Internal     Zener
DC            DC
12.3V   10.6V   4.71V
9.3V       7.8V      4.42V
12.3V    9.4V      4.65V
9.3V       7.20V   4.30V

So even on the low side of the power rail I'm getting higher voltages.  I'm not sure what power source you used but a 4.7V zener would give a range of 4.0 to 4.3V.   So from that I would guess that you unit has a 4.7V zener.

I have an old PH-1 schematic with 1K the footswitch  + flip-flip diode but it shows 5.1V zener.   So either your unit has a zener voltage on the low side of tolerance, or there's a fuzzy region where 4.7V changed to 5.1V.
I guess that a confusing result as far as placing the zener change in time.

The resistor above Q10 is 1k.

Cool.  So removing the flip-flip diode and changing the footswitch resistor from 1k to 100R probably did occur at the same time.

I shouldn't really say 1K to 100R for the footswitch as some units had 22 ohms instead of 1k.  Ultimately they all changed to 100R.

I have a TW-1 that I know is a later run, and at least one PH-1 (I think I have another that was waterlogged and beyond repair in a drawer somewhere).  I went through a period of collecting what appeared to be repairable Boss pedals.  I got quite a collection and only lost got a couple that I've not been able to fix easily.  Let me know if there's anything in these that you'd like me to check.

Thanks a lot for checking your unit.  I think the order of changes around the footswitch is pretty much worked out now.   There are other changes over time which are specific to the pedal.

I know there's at least two versions of the TW-1.  FYI, the early ones have:
- RC3403 opamp, 14 pin
- 22R on the footswitch.
- Diode on flip-flop
(really early ones are suspected to have the very early Battery check.)

Ok, it's actually the CS-2 that was sitting next to it that sounds ridiculously muffled when the effect is engaged and not the CS-1.  The CS-1 sounds as good as these things get!

I suppose if it's muffled in bypass that  really narrows it down: Sockets, Buffer Transistors, Switching JFET and output cap.  The signal will just die at some point through the chain.

[Rob Strand]

- (together?) Remove Flip-Flop emitter diode, and,
  Change footswitch series resistor from 1K to 100R.

I found and example of an SP-1 with the FF diode but 100R on the switch, so i guess the 100R change came first!

[Rob Strand]

Updated with new info,