Hi everyone,
I’m new to pedal building and am having a great time. So far I’ve built a Big Muff Pi, Tube Screamer and Honeybee from Aion. All worked as soon as they were plugged in. My luck has changed with pedal number four a Lumitron, Mu-Tron iii clone. My understanding of how circuits actually do things is almost nonexistent though I do understand the fundamentals of most components and I can read a schematic. I have a lot of troubleshooting experience, but in systems very different from pedal circuits. I have been using a Fluke multimeter and an oscilloscope for signal tracing. I have attached the schematic I’m working from and have made no modifications to the circuit.
So I set the board up for testing without any of the offboard wiring done. Everything on and battery connected… nothing. Disconnect the battery and I get signal through the unpowered board (though I’m not sure I understand how that is possible). I have triple checked all component values and orientations. All good. Voltage measurements are where things go off course. Using a battery, I got about .5V drop when connected to the circuit which draws 12mA. Seemed ok to me. What has me stumped are the voltages at the LT1054CP. Pins 1 and 8 get PS voltage as I expected. The -VA at pin 5 makes no sense to me. Looking at the data sheet (and the -VA designation on the schematic) I believe the 1054 is working as a voltage inverter. Therefore, I would expect to measure the same voltage as input except it should be negative. I admit my understanding could be totally wrong. What I measured was about 8.6V input and 0.8V at pin 5. This doesn’t seem right to me at all. The pin 8 and 5 voltages make it to the opamps as expected. Can anyone give me an idea of what to expect for the pin 5 voltage and, if it’s wrong, suggest possible sources of the problem?
I’ve done some more things but don’t want this to be too long for people to want to read
Thanks for reading I greatly appreciate any and all help you can provide!
Peter
I’m new to pedal building and am having a great time. So far I’ve built a Big Muff Pi, Tube Screamer and Honeybee from Aion. All worked as soon as they were plugged in. My luck has changed with pedal number four a Lumitron, Mu-Tron iii clone. My understanding of how circuits actually do things is almost nonexistent though I do understand the fundamentals of most components and I can read a schematic. I have a lot of troubleshooting experience, but in systems very different from pedal circuits. I have been using a Fluke multimeter and an oscilloscope for signal tracing. I have attached the schematic I’m working from and have made no modifications to the circuit.
So I set the board up for testing without any of the offboard wiring done. Everything on and battery connected… nothing. Disconnect the battery and I get signal through the unpowered board (though I’m not sure I understand how that is possible). I have triple checked all component values and orientations. All good. Voltage measurements are where things go off course. Using a battery, I got about .5V drop when connected to the circuit which draws 12mA. Seemed ok to me. What has me stumped are the voltages at the LT1054CP. Pins 1 and 8 get PS voltage as I expected. The -VA at pin 5 makes no sense to me. Looking at the data sheet (and the -VA designation on the schematic) I believe the 1054 is working as a voltage inverter. Therefore, I would expect to measure the same voltage as input except it should be negative. I admit my understanding could be totally wrong. What I measured was about 8.6V input and 0.8V at pin 5. This doesn’t seem right to me at all. The pin 8 and 5 voltages make it to the opamps as expected. Can anyone give me an idea of what to expect for the pin 5 voltage and, if it’s wrong, suggest possible sources of the problem?
I’ve done some more things but don’t want this to be too long for people to want to read
Thanks for reading I greatly appreciate any and all help you can provide!
Peter
