Boss CE-2-no effect... Mark hammer, anyone?

[Eirik]

I just bought a Boss ce-2 for next to nothing, knowing it didn't work.  It seems to be perfectly fine in bypassed mode. When I hit the switch the led ligths up as it should, but nothing happens to the sound at all, it's exactly the same as when bypassed. Can anyone help me on the way to get this thing working?
I know next to nothing about chorus circuits so it's kinda hard to know where to start.  Schematic can be found here: http://www.freeinfosociety.com/electronics/schematics/audio/bossce2.pdf

[vanhansen]

Got an audio probe? That's the first thing I'd do since we know it has power, but check the voltages with a DMM anyway to be sure it is the right amount.  If so, then take your audio probe and start at the input jack working your way through the circuit.

[Mark Hammer]

See that thing in the upper right hand corner called Q8?  That is the *true* switch for the effect.  It is an FET whose resistance is very high when the effect is off and whose resistance is low when the effect is on.  If the LED lights up, that means *part* of the switch circuit is working but it doesn't mean the delay signal is reaching the point where it gets mixed with clean signal and becomes chorus.  If you have a meter, measure the resistance between the drain and source, or rather between the end of R22 that connects to it, and pin 2 of IC1.  When the LED is on, it should read well below 1k.  If it doesn't then you may need to either replace it or check for a broken connection.

Alternatively, there is a trimpot on board.  It needs to be set just right for the delay chip to work.  Though usually quite steady and stable, they CANcome loose over time - remember, these things get stepped on and kicked for a living.  Feel free to readjust it; you will not destroy anything.  If it is misadjusted, you can tweak it to the optimum setting by ear.  Over the full rotation of the pot, you should hear a transition from no chorus, to very gritty poor quality chorus, to cleaner, then gritty, then no chorus.

See where both those take you, and we'll pick it up from there.

[Eirik]

I measured the fet and it was fine. 340ohms or so when active. So I tried the trimpot and that did it! Thank you Mark! Thanks to you I've got myself a $10 fantastic, full working, amazing sounding chorus        Time for modding  So thank you Mark again, and thanks to Vanhansen for kindly posting Marks mods on your site.
I don't have an audioprobe, but i realize it would probably be great tool for debugging and repairs.

[vanhansen]

I measured the fet and it was fine. 340ohms or so when active. So I tried the trimpot and that did it! Thank you Mark! Thanks to you I've got myself a $10 fantastic, full working, amazing sounding chorus    ;D  :icon_cool:  Time for modding  So thank you Mark again, and thanks to Vanhansen for kindly posting Marks mods on your site.
I don't have an audioprobe, but i realize it would probably be great tool for debugging and repairs.

Hey, no problem.  It was Mark who got me in to modding my CH-1 and helped me along. The CE-2 page just came naturally considering how simple the mods to both of them are.  Mark deserves all the thanks.