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It’s great to meet another engineer! That’s why I like your communication style!
Sockets might be nice to have, but I have found them to be unreliable if you are going to be gigging or traveling much with this pedal. But if you really want them then make sure you get the kind that can accommodate short component legs…because the optocouplers that you made now have short legs after you cut them off during assembly. That’s really the only suggestions I have other than use caution when removing the components from the board. They are delicate and the traces and pads on PCB are somewhat delicate too.
Good luck!
-BrachCarlos,
Thank you very much for the clear and detailed information. It is very easy to work with you in troubleshooting your pedal. I wish all our customers could communicate as well as you.
That’s no problem about the bags being thrown away. The numbers on the bags might have been helpful to me but it’s not necessary.
Thank you for the photos you emailed me. The optocouplers look mostly good, but there was one angle that kind of looked like they may need some more sealant. Here’s the edited photo…
https://zeppelindesignlabs.com/wp-content/uploads/2023/01/20230128_145356.png
…but if you tested them with your spotlight and they didn’t change resistance then they are probably sealed…but it would be good to be extra cautious in this matter just to rule out all the variables we can.
When I was designing the VPM-1 I looked into using the NSL-32 optocoupler, but it was hard to get consistent result from them…at least from the batch that I was testing. I ended up spending a couple of months developing my own rigorous test procedure for LDRs that we purchase in bulk. It ended up being way more reliable and economical for us to sort our own LDRs. But in looking at the datasheet for the NSL32SR2 (sorted) variety, they should be matched enough to work with the stereo VPM-1 (any type A-G). That’s assuming the datasheet is correct. I’ve often had a hard time getting the promised results from LDR datasheets in real-life situations. But if you have the sorted variety you can give them a try. It shouldn’t matter which optocoupler goes in which location, if they really do have those specs.
Good luck!
-BrachCarlos,
Sorry for your stereo trouble.
First of all let me ask, when your VPM-1 kit came in the mail it should have had 2 pairs of LDRs in the stereo kit bag…did it also have one extra pair in the VPM-1 main kit? If so, which 2 of the 3 pairs did you use? We accidentally sent out 3 pairs of LDRs a few times, which can be confusing.
Second, did you make sure to change all 7 jumpers when running the stereo setup routine?
Third, it would help if I can see a picture of the plastic zip lock bags that the stereo LDRs came in. It would help for me to see how the numbers were written on the bags to know what generation of test LDRs were sorted. Could you please send me a photo of them to this address?:
info “at” zeppelindesignlabs “dot” com
Forth, it might be good to add some sticky tack (poster putty) on the ends of the optocouplers just to ensure they are really sealed. Sometimes if the holes are too big nail polish won’t seal them. Make sure you run the stereo setup routine again after you do that.
-BrachThe dip switches couldn’t directly be exchanged for pots, but the resistor networks attached to them could be (maybe that’s what you were referring to). You can see from the schematic that the resistors just create a low pass filter and a high pass filter, coupled with C2 and C3. So I suppose you could exchange the resistors for a 50k (or so) pot. You’d probably want to add a minimum resistance to keep the pot from going all the way to 0 ohms.
It is also possible to exchange the trim pots for external pots, if you wanted. I designed these features to “set and forget”, but if you wanted to play around with them more, I encourage you to experiment. The main issue might be the question of where to mount the pots on the enclosure. I don’t have any suggestions about this, so your guess is as good as mine.
Good luck.
-BrachThe 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.
Good luck.
-BrachI 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…).
Good luck.
-BrachGood! I’m glad to hear that.
Did you end up running the stereo setup procedure, or did you just fix the optocouplers? I’m just curious to know what the problem ended up being.
-BrachThat’s too bad. I can get you spares for basically the price of shipping. Email us with your address and I’ll send you a paypal invoice.
-BrachI’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.
-BrachCole,
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.
-BrachI suppose all that’s really necessary to do what you want is to flip the expression dip switch (switch 4 on the main board dip switch). Repatching anything isn’t really necessary if you don’t need to use the tuning jack for your audio signal…you can just keep your expression cables plugged into the tuner/exp jack. I’ve heard of at least one customer wiring a “break-out” switch to the dip switch pads so they could more easily switch them without removing the module. That may be a good option for you. I don’t know where you’d mount the break-out switch, but electrically it should work.
…just an idea.
-BrachI just wanted to update anybody who is looking on this thread….
We’ve recently developed a mod for the VPM-1 that allows it to fit into the larger Ernie Ball volume pedals, not just the Jr. line. See the VPM-1 Large Format Adapter page for more info…https://zeppelindesignlabs.com/product/vpm-1_large_format_adapter/
-Brach
