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I am Building a Pumped Up RangeMaster Pedal and I read where the voltage between Q1 and Ground should be NEGATIVE 6.8 to 7.? volts. I have 9.026 volts between Battery Ground and Battery Positive. I am getting POSITIVE 4.9 volts between Q1 and Battery ground (with black lead on ground and red lead on Q1). When I turn the TR1 pot voltage will reduce to 0.0 voltage in one direction and maximum of POSITIVE 4.9 volts turned in the other direction. Cannot never reach the NEGATIVE voltage readings the instructions state on the bias to be in the NEGATIVE voltage. Also volume seems greatly reduced with pedal in on position. Any Ideas???
Thanks
Mack McKinzie
Post some nice clear pictures Mack so we can clearly see all components and offboard wiring to DC jack (if using one) etc
The power at the battery would be negative ground, so you would get a + voltage reading, it’s only inverted going into the circuit through the 7660S so use a circuit ground point to take voltages
It won’t actually matter youre just simply inverting the meter leads
Bias voltages are a guide I usually bias by ear to where it sounds good to me, sometimes depending on the transistor used it’ll be anything from 4.5v up to 8v
Is there any way to gain more “gain” or “Volume” with the turn knob.
It should boost pretty good Mack
It boosts the signal by around 38db afaik
The components mainly responsible for gain would be the emitter trimmer TR2 supplying negative feedback and the bypass cap C5
So I’d try adjusting TR2 and perhaps reflow solder joints I’ve built a few and it always boosts the signal
It sounds like you may have a build error what transistor did you use? If the transistor is in the wrong way it wouldn’t conduct properly
Uploaded photos so you could take a look. Sorry for the photo delay had to pick up pedal at lunch.
Cant see R2 clearly should be 200K red black black orange brown
It looks like 2K red black black brown brown but it’s out of focus so may just be the reflection
Your 7660 looks the wrong way around
Notch and dot to the right
Mack it looks like you have SW1 wired to S4, S5, S6 – these are used for wiring the stomp when you’re not using a 3PDT Board. The toggle needs to be wired to the SW1 pads on the left side of the board.
Chuck
Yes sir. I figured that out after going over board and checking everything. Thanks though for pointing it out
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