BYOC OD2 LED Problem

[vroomery]

Hey guys (and gals),

It's been a while since I've visited the fret, I just finished my last semester of college (what a weird feeling) so I haven't had much time to tinker and spend online.

Voodoo, I think I need some helpful advice on my recent build. I finally ordered myself an OD2 kit from BYOC. I'm pretty excited to see what it can do. It's all put together and sounds pretty good but the LED's aren't turning on in any predictable manner. They react to the switches, but only sometimes. For example, sometimes I'll push a switch and the LED will come on (sometimes it won't) but the next time I push it, the LED might not turn back off (sometimes it does). I'm not really sure what to do here b/c it's not a predictable situation. My first thought was to check the solder job on the LED's, but it doesn't seem like this would be the problem if they are sometimes reacting to the switches unless the physical movement of the switch (pedal casing) is causing the LED to make a better contact.

Any ideas would be amazing.

I have to say, the build quality on this pcb is phenominal. I build the TS clone from GGG and it was nothing compared to this. Even the layout is much more clean and well thought out. I don't think I'll be buying from GGG again for this very reason.

By the way. It's good to be back again and catch up with everyone. Hope everyone is doing well.

[duhvoodooman]

Is it JUST the LED's that are acting up, or do you find the effect cutting in and out when they do?

[vroomery]

I couldn't turn the amp up very loud because I'm in my apartment, but as far as I can tell it's just the LED. The sound doesn't seem to change any.

[duhvoodooman]

Some background info that you may find useful in troubleshooting this--apologies if you already know this stuff:

As in most true bypass pedals, the LED's do not indicate that the effect circuits are energized--as long as you are connected to a power source and there is a plug in the input jack, the circuits are always energized. This is why, when running on a battery, you should always disconnect the input cable from the pedal, or the battery will go dead in a day or two.

The function of the LED is merely to indicate that the footswitch is in the bypassed (LED off) or engaged (LED on) position. Consequently, the LED hookup on both sides of the OD2 is very simple and is independent of the operation of the effects circuits themselves. The anode side of the LED is connected through a current limiting resistor to the 9V power trace on the PCB. The cathode side connects to a trace terminating at eyelet 1 above the footswitch, which is wired to lug 1 of the switch (upper left as viewed from the open back of the pedal). When the switch is engaged, lug 1 connects to lug 2, which is wired to ground through the PCB to the input jack. This completes the circuit and lights the LED. When the switch is in bypass mode, lug 1 has no path to ground and the LED is off.

This simplicity dictates that an intermittently malfunctioning LED can only reasonably occur due to two basic causes:


Interruption of the 9V voltage supply (bad solder connection or short)
Interruption of the path to ground (bad solder connection or bad footswitch)

Looking at the first possibility, a power interruption could be occurring either for the entire 9V supply rail or just in the short path between the PCB power trace and the LED anode. If the issue is with the main 9V power trace itself, it will affect the entire pedal--both LED's and both effects circuits--hence my question of whether or not the effects themselves were cutting in and out with the LED's. You should double check this, since this is a critical piece of information. Further, if one LED is lit while the other not (assuming both footswitches are engaged), the problem can't be the main power connection.

If the main power connection appears to be OK, then you also want to check the solder joints of the LED itself and its current-limiting resistor. These are the 4.7 Kohm resistors adjacent to the two LEDs. Just reflow each of the resistor and LED solder joints with a touch of a hot solder iron. It's unlikely these are the problem, but you might as well eliminate them as possibilities.

The second main possibility is interruption of the ground path. As with the power, it could be a problem with the main ground connection through the input jack, but this would affect the whole pedal. So if the effects circuits work and the problem doesn't affect both LED's simultaneously, you can eliminate this as a possibility. That would leave the individual LED ground connections through the footswitches as the culprits. This could be a solder joint problem with the wiring (PCB eyelet 1 to switch lug 1 and PCB eyelet 2 to switch lug 2), or it could be a bad internal switch connection. The latter is unfortunately quite common, since these 3PDT footswitches are easily damaged if you apply too much heat to them--the plastic can actually melt and allow the lugs to move inside the switch, compromising their operation. Replacement switches can be had for about $4 each.

The best way to troubleshoot the ground path is with a multimeter set to measure continuity. If the ground path is good, you should get continuity between the cathode leg of the LED (connects to the round pad on the PCB) and the sleeve (middle) tab of the input jack when the footswitch is engaged. So fool around with the pedal until you can get the LED to stay off while the switch is engaged, and then check this path for continuity. If you don't show continuity between those two points, leave one multimeter probe contacting the input jack sleeve and work back from there through the footswitch. If you have continuity to lug 2 of the switch but not to lug 1, then the switch is bad and will need to be replaced. Be sure to place your probe on the lugs themselves and not the solder joints when testing the switch--you don't want a bad solder joint at the lug to fool you into thinking that the switch itself is bad. If the switch is OK, then one of the wiring solder joints must be at fault.

Hopefully, between all these various checks, you'll be able to pinpoint the problems. Let us know how you make out.

[marnold]

As in most true bypass pedals, the LED's do not indicate that the effect circuits are energized--as long as you are connected to a power source and there is a plug in the input jack, the circuits are always energized. This is why, when running on a battery, you should always disconnect the input cable from the pedal, or the battery will go dead in a day or two.
[Johnny Carson]I did not know that![/Johnny Carson]

Of course, I run everything except my EX-7 off the 1-Spot so it's a non-issue. The EX-7 has it's own power supply because it sucks so many mAh.

[vroomery]

So after almost 6 months of just guessing when my OD was turned on, I finally got annoyed enough to fix it. DVM, your explanation was brilliant. The only thing that was being affected was the LED's themselves, and it was only on the OD side, not the boost side. I took a small screwdriver and bridged 1 and 2 of the OD switch and it came right on. I then re-soldered those lugs as well as the rest of the switch and and now it works just fine. I took this opportunity to throw in some blue LED's instead of the given red ones. Looks way better. Thanks for your help as always!