Just to get you Hot 'n Bothered....
Posted: Mon Mar 23, 2015 5:06 pm
I've started digging into the Rand-O-Matic over at DIYSB's.
The component and trace picture are high resolution, so download them, and blow them up on your computer.
Control reference;
Trace side (note that the image is reversed, so I could use it to copy the components onto it);
Components;
Note that the two TL064's are upside down vis-à-vis the square pad indication of the board. There must have been an error in the original board layout. Follow my indications in picture.
Top side traces;
Ironically, I found that one of the 10K trimmers (above IC12) was actually broken. It controlled the amount of maximum feedback. For some reason, it had been pried off the board somewhat, enough to break the wiper lead. It explained why I found the feedback control rather weak. I removed it, and replaced it with a new multi-turn, and I have now adjusted it to where max feedback will take the input signal into runaway oscillation, which is kind of cool.
I'm going to go over it some more to ensure that there are no errors, missing connections, etc. The tantalum caps around IC1 are a bit of a crap shoot. Other than the polarity markings, there is no values on them. Measuring them in place with my capacitance meter, I get readings of 82nF to 88nF. They are slightly smaller than a 1uF cap that is on the board, so I'm making an educated guess here. I'm not really keen on removing one just to measure. IC1 looks like a dual opamp for mixing the dry and wet signals.
My partner in crime UKToecutter has once again taken up the challenge of confectioning the schematic, and will probably do the clone PCB for it, but we still need to figure out the remaining unknown IC's.
Hey... nobody said it was supposed to be easy.
The component and trace picture are high resolution, so download them, and blow them up on your computer.
Control reference;
Trace side (note that the image is reversed, so I could use it to copy the components onto it);
Components;
Note that the two TL064's are upside down vis-à-vis the square pad indication of the board. There must have been an error in the original board layout. Follow my indications in picture.
Top side traces;
Ironically, I found that one of the 10K trimmers (above IC12) was actually broken. It controlled the amount of maximum feedback. For some reason, it had been pried off the board somewhat, enough to break the wiper lead. It explained why I found the feedback control rather weak. I removed it, and replaced it with a new multi-turn, and I have now adjusted it to where max feedback will take the input signal into runaway oscillation, which is kind of cool.
I'm going to go over it some more to ensure that there are no errors, missing connections, etc. The tantalum caps around IC1 are a bit of a crap shoot. Other than the polarity markings, there is no values on them. Measuring them in place with my capacitance meter, I get readings of 82nF to 88nF. They are slightly smaller than a 1uF cap that is on the board, so I'm making an educated guess here. I'm not really keen on removing one just to measure. IC1 looks like a dual opamp for mixing the dry and wet signals.
My partner in crime UKToecutter has once again taken up the challenge of confectioning the schematic, and will probably do the clone PCB for it, but we still need to figure out the remaining unknown IC's.
Hey... nobody said it was supposed to be easy.
