Home › Forums › VPM-1 Forum › something broke
- This topic has 10 replies, 2 voices, and was last updated 3 years ago by brach.
It was working great at first, but now I cannot get 0 volume. Tried recalibrating without success, different tapers make no difference as well. It seems like the volume begins to decrease, but then goes back up as the pedal travels further. Any suggestions where to start troubleshooting appreciated.
What is the serial number?
Is this a kit build or did you get it ready to install?
Kit built, ZD4462
I tried resoldering a couple joints that looked a little suspect, and now it doesn’t do anything. So if there’s a schematic available, I could take it to the local eletronics repair guy and see if he can find anything. If not, it’s toast.
I’m in the process of writing a troubleshooting guide for the VPM-1…but it’s been hard to finish due to the pandemic and me not working at the lab much.
As far as the volume not turning off…check the optocouplers (especially on the LED side) to make sure that one of the heat shrink tubes didn’t pop open, or has an “optical” leak that could let light in. If so seal it with some opaque material…like caulk or even sticky tack (poster putty). I use black hot glue for this.
You can also try to re-setup the microcontroller’s memory registers by running through the stereo set up procedure. To do this jump together the 2 pads of “CAL1” as you plug in the power. Once the power is on you can remove the jumper…i just use my metal tweezers to short the pads together upon power-up. The red LED will start flashing for a couple of minutes as it re-writes the registers. It will flash 256 times, if you care to count. When it is done writing, the green LED will start flashing, letting you know that you can unplug the power and remove the jumper if it’s still on.
As far as it not working anymore, what do you mean? Does the LED turn on? If not, check your DC jack to make sure the wires are still intact. Then check to make sure the voltage regulator is putting out 5V, which powers the microcontroller, which light up the LED.
As always, check for solder shorts with your magnifying glass.
Let me know what you find.
Thanks Brach. The optocouplers were what I tried working on yesterday. Yes, the LED turns on and goes through the color progression, but it passes no signal now. Will try some further tests later and report back.
Ok. Good luck!
No luck. No solder shorts that I can see, and wouldn’t that have shown up straight away, rather than after a few days of working? Voltage regulator checks out, rewrote the registers, and still no sound going through.
Yes, it is odd that it stopped working after it was working. Most likely it’s something simple.
I’m assuming all the switches on the dip switch are in the off position, correct?
I’m also assuming the ribbon cable is installed the correct way around (not twisted)…and has been calibrated AFTER it has been installed correctly. If it was calibrated when it wasn’t connected correctly then the microcontroller will have bad data and it won’t pass signal.
I’m also assuming that the jumpers, J5 and J6, are installed.
Just to make sure the jacks are working correctly…while the main board is in the chassis and the pedal is powered and plugged into an amp and guitar, try to firmly wiggle the input and output jacks as you play guitar….just to see if the signal jumps in and out.
Please check out those things and let me know.
Something simple, like a bad solder joint on the output jack? Yeah… 🙁 I spent all my time with the magnifier looking at the small component joints, and none on the jack connections because those are “easy”. Sorry to waste your time chasing this around, it’s working as expected now.
That’s good. I’m glad it’s back to working properly now.
Glad I could help.