Fender EXP-1 expression pedal issue

[daz]

I know absolutely nothing about digital control circuits so i want to see if this is an issue thats obvious to those who do. This pedal has 2 LEDs, 1 green and 1 red. When i try and use it with my modeling amp (which it is made to work with, so it's not a compatibility issue, it doesn't work right which i'll describe in a second. But so you know, i took the circuit board and all out of the pedal and mounted it in a pedal board to use as a simple volume boost switch. So in the amp you program the heel and toes settings for the amount of volume you want. I set it so one is 10% lower in volume so when i kick it to the red led i get a 10% volume boost. It's worked like that for a long time then all of a sudden it started malfunctioning. I took the circuit board out the housing i had it in to troubleshoot it and pressing the circuit board mounted momentary switch sometimes goes from one led to the other as it should, other times the lit led will flicker but not change to the other led. Then at times they both are on at the same time and other times neither is on. And the volume settings sometimes trigger, sometimes goes quiet altogether, sometimes works and most any time i can move the circuit board around and the sound or leds or both will change.

Now i know that sounds like a bad joint or such. But i hit every joint and inspected them with a 7x eye loupe and even replaced the 3 wires that goes from the board to a little 1/2" board that houses the sensor the pedal swipes. (covered with heat shrink so it doesn't sense anything) And no one thing affects it if i bend and chop stick the thing. It's impossible to narrow it to a certain area so i don't think it's a intermittent connection. I have no schematic so i know no one can likely help, but i thought maybe this could be a common issue that someone knows of with these types of devices and point me to a likely component. It;s not the amp either because it stopped working and i later bought the new version of the amp and it does it with that one too. Any ideas? Thank you.

[g1]

Any way you can rule out the switch? Maybe remove it and put some wires there you can touch together as momentary contact?
It doesn't really sound like a switch problem to me, but it would be nice to be 100% sure.
Another possibility is stray capacitance or resistance triggering the switch circuit. Any excess flux you can clean off with isopropyl?

[daz]

I was kind of thinking the electrolytic because wouldn't that being somewhat bad cause the voltages to vary? I would think that could cause it but i didn't want to pull it just yet as much of a pain this double sided board is. the switch is fine, i've already check that out well. But thats got nothing to do with most of the symptoms anyways. theres some flux, i'll try that first, Thanks g.

[eschertron]

What about the power supply? That's my first suspicion from your post. At least power-to-the-control-unit-supply. Your guess about the cap (caps?) is in line with this. That said, the only thin I know about digital electronics is that there are commonly small-value caps right on the power supply pins of each chip to prevent noise from being interpreted as signal. Do you think this pedal is robust or marginal with placement of these caps?

[daz]

The power is supplied in the amp, and i know it's not in there because i bought the amp and returned it for a defective grill and the exp1 still does it with the second amp, as well as my original one i have had for 4 years. I paralleled another cap with it and same result so probably not that.

[daz]

AH haaaaa ! I got it, and it was one of those double wammys where you found the problem and fixed it but didn't know it was fixed. I'll explain. It wasn't working so i replaced a 3 wire ribbon i suspected. I had been using it plugged into a 4 button footswitch for the amp and the exp1 plugs into that. When i replaced the wires that apparently fixed it, but i tested it plugged directly into the amp instead of the 4 button and apparently it cannot be used without the 4 button switch, at least not in this amp model. So i plugged it into the 4 button and wham bam, it's workin' ma'mm ! And whats more...how i figured it out....i did a search here for exp1 hoping maybe someone else had had the same issue and found an old post BY ME asking about something regarding it and as soon as i saw myself having typed something about it must be plugged into the 4 button i stopped reading and immediately plugged it in that way. What a friggin relief ! I'm out of work for a long time now and can't afford to spend $90 to have a simple volume boost. It was all i could do to convince mysef to buy this new amp. so one way or another this forum always helps me out in the end, even if it was ME who helped me !

[daz]

F it. Still screwing up. electronics are the bane of my effing existence.

[daz]

Hey guys, answer me this....the old amp has 3.26 VDC coming off the footswitch plug with no load. The new one has 3.56 VDC. Being a control voltage i;d think it would be very sensitive to variances. Could that slight difference have anything to do with it? If so should i try dropping it and how would i try this safely. I don't wanna burn out a component in the switching system on a new amp.