I completed my build last night and am curious to know if other have had the same issue I am having and how it was resolved. I did not add stereo or expression upgrades to my build.
In the troubleshooting guide, C.4 on pg 3 advises to test voltage on the pins of U2. I am unable to locate U2.
The reason I am troubleshooting, is that it seems I get no audio signal from the pedal input. The pedal powers up and I was able to successfully calibrate. When turning the gain knob, I can hear somewhat of an audio hiss that changes when activating the treadle. This leads me to believe that the sensor seems to be working and there is signal from output to amp. Oddly, this hiss seems to be in reverse as it goes completely silent when the treadle is open. The DIP is not set to reverse.
I’m sorry about your VPM-1 issues.
U2 is labeled on the voltage chart. It’s the IC in the middle of the board. Make sure the pins are -9v and +9v, as labeled.
You pedal’s symptoms are odd. It kind of sounds like the microcontroller may be screwy. You may want to do step D-3…it could fix the issue. The other thing to check would be to ensure the LEDs in the optocouplers are orientated correctly…the long pins should be in the square holes. Check that stuff and report back.
Hey thanks for the quick reply! I looked all over that diagram and completely missed that haha.
All voltages seemed to be reading correctly throughout the whole board per the voltage chart. I did pull the optocouplers last night and will need to rebuild them to verify polarity as I had to cut the led legs short. I’m assuming that green LEDs were used for intensity rather than red? Pretty sure I have some green 3mm somewhere, but I know I have some red for sure. Once I rebuild and place the optocouplers, I will do step D-3 (I have no idea why I didn’t try that before I pulled the optocouplers haha). Will report back asap.
I’m sorry, I wasn’t meaning for you to have to remove the optocouplers. The LED’s polarity should be tested using your meter’s diode tester. With the red probe on the LED’s square pad and the black probe on the round pad, the meter should read around 1.8V (which is the forward voltage drop of the LED). If it reads around 1.5V then reverse the probes and check again. If when reversing the leads (red on round, black on square) it gives a reading of 1.8V, it means the LED is in backwards.
The LED’s turn-on current is rather specific for this application so please don’t use just any 5mm (not 3mm) green LEDs. I don’t remember the specs off the top of my head, so if you do need to replace the LEDs then let me know and I’ll try to find the specs you need to use…hopefully you don’t have to replace the LEDs.
If the LEDs in the optocouplers were in the correct orientation, I was going to have you make a small cut in the heat shrink so you can see what the LEDs are doing as the treadle is moving. You can always repair the cut with caulk or sticky tack or opaque hot glue or something. But this will give you a good idea if the problem is with the digital circuit or analog circuit.
Hey just wanted to follow up. I received the LEDs today. Thanks so much for the quick turnaround! I rebuilt the optocouplers and dropped them in and have good clear audio! Thanks again for the help and quick response!
So far just the optocouplers. I will do the stereo setup tomorrow. I believe I’ve calibrated the pedal properly but the taper seems to be off. It seems like an abrupt audio on with only a slight tapered increase in volume. It doesn’t seem to change when changing the taper button. Hoping the stereo setup will fix.
I would guess that it needs the stereo setup routine run. You also should re-calibrate it after doing any major change with the optocouplers. But this symptom could be caused by ambient light getting into one of the optocouplers. Just make sure there are no holes on the ends of either optocouplers that light can get in. If you aren’t sure, you might want to seal them (just to be safe) with something opaque (caulk, sticky-tack, opaque hot glue, etc…).
I calibrated right after redoing the optos. I also sealed both ends of each with black liquid tape, so there shouldn’t be any ambient light getting in. I started to do the stereo process, but ran into a new problem… For some reason, there is now no green illumination from the rgb led. I don’t see any apparent shorts and all solder points are in tact. The rgb was fully cycling prior to pulling the optos, but I’m not sure how that would have caused this new issue. Any thoughts?
Also, you have no idea how much I appreciate your patience through all of this!
The green LED issue must have happened when you pulled or replaced the LEDs. Do diode tests on all the pins of the RGB LED (the square pad is ground). The green pin is the one connected to R19 (the pin between the square pad and the pin closest to the ISP header). Use your continuity tester to check for shorts around the LED. You can also make sure the other side of R19 is going high when the green LED should be on.
Proud to report that it works perfectly now. I just needed to add a tad bit more solder on that green lead of the rgb. Ran the studio setup, recalibrated and it’s good to go! Can’t thank you enough for all your help, Brach. I look forward to supporting you in the future and spread the word about ZDL!