Boss CE-2

[lowell]

This pedal came in totally dead. No bypass or effected audio. I began poking around reading voltages and discovered that the filter cap on the trim pot's output C18 was shorted. Replaced it and the pedal came back to life. I am still however only getting 6vDC on the main power rail. This is with a GOOD battery and/or 200ma DC wall supply. I disconnected the main rails' filter caps one-by-one to see if the voltage came back up, but nothing. Also, the ON/OFF LED is so dim when it's ON that I have to turn ALL the lights out and put my eyeball up against it to see it. I'm sure this is a symptom of the low V. Otherwise the thing sounds fine, perfectly fine. I'm debating just leaving it, but there's a little voice telling me to fix the issue.

Any advice on narrowing down what's loading the rails? There are so many potential culprits.
Schematic is here: http://www.hobby-hour.com/electronic...-schematic.gif

[g1]

I would try disconnecting D7 on battery power and see if it comes up.
Possibly it got replaced with the wrong voltage (6V instead of 9V).

[Enzo]

I agree, lift D7. My own mental scenario is that someone plugged the wrong power adaptor into it, shorting or damaging that diode. Instead of zenering at 9 or 10v, it collapsed to 6v.

[lowell]

Duh I failed to mention that was suspect #1. I had already lifted it. Next?

[g1]

Check current consumption using battery.

[Enzo]

Lift the 33 ohm, that will divide power supply draw into BBD chip circuits and the rest of the thing. Does the 9v come back up?

[lowell]

Good idea...lemme check

[lowell]

Disconnecting the 33ohm didn't help. I then began taking more voltage measurements and realized if I used the DC jack as ground that I did indeed have 9v in some places. Tracked it down to 2 solder pads next to each other that were no longer measuring as connected. Trace must have cracked right there. Soldered em and the pedal works great, voltages measure out, LED lights brightly. NOW... I've been scratching my head cause using a battery doesn't work. I checked that the input jack is indeed shorting the negative lead to ground, the DC jack is indeed shorting the +9v lead to the circuit board. I am only getting 600mv on the V+ line. I checked and double checked my battery, measures good out of circuit. I completely removed the battery leads and used alligator clips. I thought maybe the zener or the initial supply might be leaky so I lifted them. I lifted the polarity protection diode as well. None of these made the battery 9v come up. Could I have a bad battery? It's the only one I have here right now. For some reason the battery isn't keeping up with the current but the Wall adapter IS. Oh and not sure if this matters but the DC resistance of the + supply line to ground is measuring ~5k. The 600mv I'm getting is suspiciously close to a diode's forward voltage drop.

[Jazz P Bass]

The Vac adapter is probably capable of providing more current.
What is it's rating?
Is it a 'switcher' or a transformer?

Try Enzo's Post#6.

That will certainly narrow it down.

[lowell]

The adapter is a 200ma rating. It's a transformer.

I found a Duracell and it definitely holds up BETTER, but still is low voltage when in circuit and I can watch the voltage dropping... about 10mv a second. I'll keep lifting things to find it.

[Enzo]

You said lifting the 33 ohm didn't help, but you didn't say what it DID. By lifting it, of course the thing won't work, but it eliminated a good portion of the circuits, so the left end of the 33 is the only part powered, BUT does that powered portion still drag the voltage down or does the voltage stay up now. That was the whole point of lifting it, it divided the circuit in half.

[lowell]

Correct. I had lifted it for the original problem. I've yet to lift it for this battery issue... Will do when I'm back at it. Nothing changed when I previously lifted...but I was troubleshooting the 6v issue, not the battery supply... this is a new problem so I need to do it again.

[Enzo]

Whatever loaded the 9v down to 6v could still be involved with sucking up batteries.

[lowell]

Well I've hit a wall with this thing. Ive lifted the 33ohm with no change. I then measured Vbe of the transistors that are powered by the MAIN suppy (PRE 33ohm SUPPLY). Q1,2,3 all have 600mv Vbe. There is no D3 on the switching transistors emitters. It is just grounded. I lifted that ground...didnt help. Lifted R33 on the 9v/2 supply.. Didnt help. Disconnected 9v rail from IC1...didnt help. Lifted R14 on IC3 pins 7/8...no helpy.

I'm stuck. The dang thing works perfect with the 9v 200ma adapter.

[lowell]

Ok so wife returned with fresh 9v DURACELL batteries right when I posted that. Fixed it. Don't use off-brand batteries! I was using an old duracell and a EH 9v. Neither of which were able to deliver the current. Wow. Enlightening. I will only use Duracell from now on. I always have...but this further confirmed it.