Early Boss CE-2 LED works, but no modulation

[Hagstrom71]

I have a made in japan black label Boss CE-2 that receives power as the led is bright red, but there is no modulation.
I do hear the tone change when engaged, and if I move the knobs I hear a slight chorus effect.
Nothing appears to be burned that I can see on the circuit board and solder joints look good.
If anyone here has any suggestions on where to start troubleshooting, or any good websites to research I would be grateful.

It's been a while since I used this pedal and at first I plugged my 1spot to power supply into it before I remembered that I need it placed between other pedals when using a 1spot or just power via 9v battery. Not sure if this may have damaged it, since I would think the LED would not work at all.

-Chris

[Laservampire]

I think there is a mini pot on the board that controls the chorus intensity (I know the later Taiwan CE-2s have it because you can tweak them to sound just like a Japan one!), possibly the issue?

[Scruffie]

The trimmer on the board is for the bias, it shouldn't be adjusted until the cause of the issue has been determined.

From you saying it's been a while since you used it and shifting the knobs gives a slight chorus effect my first educated guess would be an electro cap has gone bad around the LFO/VCO section but you need to post full voltage readings from all the Op-Amps first before i'd want to make that judgement.

The 1 spot issue is likely down to the zener diode, they originally used a 10V supply, no harm should have come to it.

[Hagstrom71]

Thanks for the replies.
I've always heard to leave the trim pot alone, though I have been tempted adjust it.
I'll start getting voltage readings and post when work dies down a little.
Right when I was ready to work on a faulty pedal, work gets busy.. I should have tried fixing it sooner.

[Scruffie]

It wont harm anything if you do play with it, it's just that to adjust it properly you really need a scope and it's probably still set where it should be, obviously some times it does turn out to be the problem but because it's the easiest thing to try it gets played with first and if it's set wrong that can make the rest of the debugging harder as in the wrong position the BBD wont pass any signal.

No problem, I'll keep an eye on the thread for when you're ready.

[pothole]

Years ago I bought a broken DM-2 delay that did that...for like $20....light was on but no delay. I just popped the BBD out and sprayed it with some cleaner and reinstalled and it worked like a champ. I probably just got lucky though.

[FUZZTX]

You may try an old Boss ACA power supply. I had the same issue with a DM-3 and come to find out it needed the ACA power supply and it works fine.

[devnulljp]

You may try an old Boss ACA power supply. I had the same issue with a DM-3 and come to find out it needed the ACA power supply and it works fine.

This. IIRC those pedals require 12V not 9V. But first, try it with a 9V battery. If it works, then there's prob nothing wrong with it. Next try daisy chaining the 9V power supply with another pedal. Again, if it works that's your issue.
I wouldn't try plugging in a 12V power supply til I'd figured out that's the issue just in case it's been modded for 9V and you end up frying it. The tests above won't do any harm either way.

[Hagstrom71]

Hey thanks for the recent posts. You guys read my mind, as I put this off a while back but have recently been thinking of trying to get it working.
I did try a 9v battery, then I daisy chained a 9v power supply with another pedal before and after. Still no chorus effect, but it does give a slight chorus effect when turning the knobs.

I'm a little green on how to measure the Op-amp voltage as Scruffie suggested a while back. Do I check each leg of each op amp in reference to chassis ground to measure voltage?
Op-amps appear to be C4558C, MN3007 and MN3101.
Any info you guys can share on how to troubleshoot this CE-2 is appreciated.

[Scruffie]

Do I check each leg of each op amp in reference to chassis ground to measure voltage?

That's exactly right, black lead to chassis, red lead to the IC pins, use the 20V setting on your multimeter.

Set the rate fully CCW and the depth CW before you measure.

Write down the measurements like this
1 - 2~7V
2 - 4.5V
etc


(Notch or dot indicating top of the chip)

You just need to measure the chip (Should be a TL022) in the top left of this photo for now, under the 104k capacitor.