RobinMallard
Member
Yeah... this pedal again...
The main issue (so far) is that I have no voltage at TP1. I saw the other posts about R15, so I had removed the 1k5 I had and put in a 10R trim pot so that I could adjust to accommodate for head dissipation (I did also add heat sinks) - although I don't have to worry about heat at the moment, since it seems that Q4 (IRF9510) isn't passing anything.
I checked for continuity to ground throughout the pedal and it doesn't seem that voltage is just going to ground. When I measure the voltages at Q4, I get 12.3 V (my power supply, rated to 1A) at the source, 11.7 V at the gate and 0 V at the drain.
I tested the other IFR9510 I have and that one has a Vg of ~3.5 V (and these seem to have gate voltages of 2-4 V overall), so it seems to me that the gate voltage isn't low enough for the MOSFET to pass signal.
I measure 10k when the BC557 is removed from the Collector to ground.
Any thoughts on what other people's voltage at the gate is for their pedals? I've taken out the trim pot in case that was causing some issue and put in sockets to try out R15's, but nothing seems to affect the gate voltage.
Since I had populated the parts (mostly) for the enhanced mixer (I left out the final coupling cap), I have a ~6V source so I connecting that to the gate (with the BC557 removed), and in that case I do get intermittent voltage at TP1, but R15 gets really hot (the MOSFETS don't).
I've also tried removing the heatsinks in case that was causing issues, but nothing changes.
I've added some photos of the front and back and the portion of the schematic related to this area.
Thanks for any help!
The main issue (so far) is that I have no voltage at TP1. I saw the other posts about R15, so I had removed the 1k5 I had and put in a 10R trim pot so that I could adjust to accommodate for head dissipation (I did also add heat sinks) - although I don't have to worry about heat at the moment, since it seems that Q4 (IRF9510) isn't passing anything.
I checked for continuity to ground throughout the pedal and it doesn't seem that voltage is just going to ground. When I measure the voltages at Q4, I get 12.3 V (my power supply, rated to 1A) at the source, 11.7 V at the gate and 0 V at the drain.
I tested the other IFR9510 I have and that one has a Vg of ~3.5 V (and these seem to have gate voltages of 2-4 V overall), so it seems to me that the gate voltage isn't low enough for the MOSFET to pass signal.
I measure 10k when the BC557 is removed from the Collector to ground.
Any thoughts on what other people's voltage at the gate is for their pedals? I've taken out the trim pot in case that was causing some issue and put in sockets to try out R15's, but nothing seems to affect the gate voltage.
Since I had populated the parts (mostly) for the enhanced mixer (I left out the final coupling cap), I have a ~6V source so I connecting that to the gate (with the BC557 removed), and in that case I do get intermittent voltage at TP1, but R15 gets really hot (the MOSFETS don't).
I've also tried removing the heatsinks in case that was causing issues, but nothing changes.
I've added some photos of the front and back and the portion of the schematic related to this area.
Thanks for any help!
