Boss CE-2 power/effect issue

[Snufkinoob]

Picked up a CE-2 a short while back, and every so often an odd problem. Sometimes it works fine, other times this happens:

It powers up with 9v power supply or 9v battery. The LED lights up but there is no chorus effect. Switch it to bypass, the LED goes off, and my clean signal is fine. Obviously with Boss effects, when you disconnect the power, you can't even pass a clean signal, so it's partly getting power okay.

I've tried different jacks on both in and out, checked the wiring, used contact cleaner on the jacks etc, but it still does it. It's been on my board between two other pedals working fine, then out of nowhere, the effect doesn't respond. Take it out, clean it etc, put it back it works, then it stops again.

I know about the 12v/9v issue with these old Boss pedals, in that it can run off a 9v battery but only a 12v power supply, because back in the day, Boss only wanted you to use their supplies, and they incorporated a diode and resistor to take it down to 9v when it hit the circuit. Anyway... the guy who I bought it off said that he had it modified to take a regular 9v supply but couldn't remember what method he used. The standard method IRRC is to remove the diode and jumper the resistor at the 9v connection. Inside it appears he's just connected pins 3 & 4, leaving the diode and resistor in. (3 goes to 9v- and 4 goes to 9v power supply connector ground.) 

I should note that I've replaced some of the electrolytic caps with metal film caps (Wampler book of mods), but the solder joins are fine.

Here's what the the weird 9v connection mod looks like:






Here's the flipside of the circuit layout for reference:




Any ideas? Nothing else appears broken, shorting out, badly connected etc.

[GibsonGM]

This is a strange one, yes.  All I could suggest is that there could be a dodgy connection in the FET switching area...a short....a bad cap...something's 'up' with the switch...you'll probably want to track down the Boss schematic and examine how it switches, what parts make it up.    Then go in and have a look, measure all your voltages.

Make sure whatever mod was done to run on the 9V adapter is providing 9V, of course.  Tap around, make sure there is not an intermittent connection.

If you can get a set of voltages for each FET when running normal, then when it's malfunctioning, it might reveal where the problem is.  Sorry I have nothing more specific.   I know a few ppl have had cap issues with the switching...


This is basically how the switching works:
http://www.geofex.com/Article_Folders/bosstech.pdf

[drummer4gc]

Do you mean that You get no signal or only clean signal when turning the pedal on? Its probably time for the audio probe.

[Mark Hammer]

Several Boss service notes I've come across note the following:

"Replace 470pf (in flip flop) with 220pf if flip-flop becomes unstable at lower supply voltages"

[reddesert]

The circuit board picture appears to show the wire jumping (shorting across) the resistor and the diode. I would prefer this to removing the components because it's minimally invasive.

Don't change any components before you audio-probe and test some voltages to figure out what's going on. If the LED switches properly but the effect does not, it's probably not the flip-flop. Test the voltages on the switch FET, audio-probe, etc. It can always be something as simple as a loose ground wire.

[Snufkinoob]

Bump.

The problem is still coming and going despite some slight tinkering. It seems there are four 470pfs in the flip-flop, C24, 25, 26, 27. Although the first two from the foot switch (C26,27) are already 220pf (stock by the looks of it). So would the other two also need changing as well? Hammer's quote just says singular, not plural. A misprint or typo?

FWIW I've cut the connection between the 9v and diode, and it still doesn't work, even with a battery. LED lights, signal has no effect and stays clean.

Any more suggestions?

[Alex83tele]

I've got two pedals with malfunctioning flip-flop circuits in line for repair. I've done a little research, but haven't found any trends pointing towards a single culprit. I've come to the conclusion that I'm just going to replace the caps and transistors, and go from there. Here's why, electrolytic caps are manufactured to a standard based on hours of operation at the rated temperature. They dry out. What happens at that point is anyone's guess. I've seen disagreement over this before, but they're cheap. Transistors are usually cheap, although I haven't sourced them, and in order to run tests, I'll have to remove them anyway. Might as well get a fresh start. With those components removed, I can test the resistors. That's my plan as of now. I've tested the switches, but I should probably run some more tests with the circuit together. However, like in your case, I know it's getting power because it's passing signal. It's just not flipping or flopping. But I've got one stuck in "On" mode, with no LED. This leads me to believe that one way or another, one of the bases is no longer saturating properly. With an intermittent problem, it can be difficult to detect unless you have a very, very nice multimeter that will monitor and track the circuit over time. The LED doesn't bother me, because it's on yet another type of transistor. If the circuit is off balance, the mosfet could react differently. All sources I find state you can't reliably test a transistor in a circuit, and I doubt that having two transistors connected across each others bases and emitters makes it better. I'm a few days behind you on getting started, but I'll let you know if I find anything.


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[Snufkinoob]

Bump. Might just order the flip-flop parts, unless anyone has a solution?

[Snufkinoob]

Six month BUMP

Figured I might as well bump this since I was posting. I replaced the caps and transistors in the flip-flop, but still the same results. I even re-wired the whole thing and no change. Sometimes works, sometimes doesn't, but lights up and passes the clean signal.

[jojokeo]

Probably not of much help but you never know right? Sometimes I will stress (flex) a circuit board carefully in bright light w/ magnification and maybe you might find a hairline crack in a trace or solder contact? It could've been dropped or worse and you never know when it comes to intermittent issues that don't make a lot of sense? If this can be done while the circuit it on and playing (using a looper?) then you just might get the behavior to show itself this way?

[Snufkinoob]

Flexing the circuit a little sounds like a good idea. I've had the back off, playing, and sometimes if I press down on the board, it works for some reason, so that might be an indication of a hairline crack somewhere.

[Snufkinoob]

9 month bump!

Problem fixed itself. Seems fine for ages, @#$%s up again. Finally got round to having another look, re-soldering etc, nothing. Open it up, move the board... Sometimes works! ... give it the tiniest of nudges.. stops... starts. Put the lid back on... Works... then doesn't. Driving me out of my mind. Schrodinger's CE-2. A circuit that is both dead and alive at the same time.

It's probably some microscopic thread bridging a gap and shorting something out, but other than that does anyone have any ideas? When I'm feeling patient I'll get the multi-meter and take some voltage readings, but it's a big circuit, so where are the key points I should be testing?

[ElectricDruid]

It does sound like a hairline crack somewhere. Another similar thing is a solder joint that has separated from the PCB trace and is only attached to the component leg, or vice versa. Mostly they'll touch and it'll work, but then a change in temperature or a movement or something, and it'll go bad again. Usually all that is required is reheating the joint. Similarly for hairline cracks - you can usually scrape off a little solder mask and solder over them.

I'd reheat anything that looks suspicious, and I'd check anything that's potentially been subjected to any sort of movement for cracks or bad joints. Over time, a bit of minor movement in a wire can make a joint come loose. This is most likely on anything that has plugs shoved in and yanked out - the DC socket, the jacks. Sometimes also the pots if they're wired and the nuts come loose.

Good luck!

[Ben N]

+1 to ED. In my experience, the Achilles heel of supposedly unbreakable Boss pedals is all of the board mounting of physically stressed components. Jacks are the worst, although I'm not sure how a crack near a jack could result in your symptoms, but it's probably worth checking continuity and reflowing a few solder joints just to be sure.