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Step 9Initial Testing
Oh, fun! With everything wired up you can actually test the circuit.
The first thing to do is to measure the power supply rails for shorts. With a multimeter, measure all the combinations of +15V, -15V, +5V and Ground and be sure none of them read zero ohms. Next, plug in your power supply without the Prism circuit board connected, and make sure you have the right voltages coming from the right pins. All set? Ok, so far, so good...
Plug the following external controls into the board, making sure that pin 1 on the connector goes to pin 1 on the board: LFO control (with switch turned off), Sync control (with switch turned off), rangefinder, and any three of the phototransistors. Don't hook up your amp or headphones yet - instead, connect an oscilloscope to the output, or at the very least a multimeter set to DC voltage.
Power it up, and see what happens. Ideally, nothing special. If you see smoke, UNPLUG EVERYTHING! You made a mistake - go back and fix it (and replace whatever part made the smoke). Ideally, there should be a waveform of some sort visible on the oscilloscope, most likely with a DC offset. If you're just using a multimeter, you may just see a steady DC voltage. The first thing to do is to adjust the offset, this is done by turning trimpot R33. Adjust it so that the DC offset is as close to 0V as possible. Note that the sine waveform controls (Rxx and Rxx) will mess up the offset to the point that you can't get it to 0V - if that's the case, adjust the sine shape trimpots at the same time.
The rest of the calibration is virtually the same as described on this page. Follow those instructions and you should do fine. Note that movement around the range sensor will cause the frequency to change (as it should) - if this makes the circuit too hard to tune, then plug the skew control potentiometer into the range finder's input, and set it to about mid-level. It will remain stable while you're tuning.
If you have a scope, you can also test the function of the LFO and Sync generators. Probe the LFO on pin 2 of the LFO XR2206, and pin 3 on the 555 timer. Adjusting the controls should cause their output frequencies to change accordingly.
Hopefully, everything will work out the first time. I spent countless late nights working out the bugs in my design so it should work fine for you. If something isn't working, I've found the top causes to be:
1. Solder shorts
2. unsoldered pins
3. backwards and incorrect parts
4. debris or bits of wire on the board
5. bad connector/wire connections
If you have a scope, it's pretty easy to trace the route a signal takes, and note where it stops (or gets messed up or whatever). With just a multimeter you can still do some testing, such as making sure the chips are getting power, and checking DC voltage levels where appropriate.
The first thing to do is to measure the power supply rails for shorts. With a multimeter, measure all the combinations of +15V, -15V, +5V and Ground and be sure none of them read zero ohms. Next, plug in your power supply without the Prism circuit board connected, and make sure you have the right voltages coming from the right pins. All set? Ok, so far, so good...
Plug the following external controls into the board, making sure that pin 1 on the connector goes to pin 1 on the board: LFO control (with switch turned off), Sync control (with switch turned off), rangefinder, and any three of the phototransistors. Don't hook up your amp or headphones yet - instead, connect an oscilloscope to the output, or at the very least a multimeter set to DC voltage.
Power it up, and see what happens. Ideally, nothing special. If you see smoke, UNPLUG EVERYTHING! You made a mistake - go back and fix it (and replace whatever part made the smoke). Ideally, there should be a waveform of some sort visible on the oscilloscope, most likely with a DC offset. If you're just using a multimeter, you may just see a steady DC voltage. The first thing to do is to adjust the offset, this is done by turning trimpot R33. Adjust it so that the DC offset is as close to 0V as possible. Note that the sine waveform controls (Rxx and Rxx) will mess up the offset to the point that you can't get it to 0V - if that's the case, adjust the sine shape trimpots at the same time.
The rest of the calibration is virtually the same as described on this page. Follow those instructions and you should do fine. Note that movement around the range sensor will cause the frequency to change (as it should) - if this makes the circuit too hard to tune, then plug the skew control potentiometer into the range finder's input, and set it to about mid-level. It will remain stable while you're tuning.
If you have a scope, you can also test the function of the LFO and Sync generators. Probe the LFO on pin 2 of the LFO XR2206, and pin 3 on the 555 timer. Adjusting the controls should cause their output frequencies to change accordingly.
Hopefully, everything will work out the first time. I spent countless late nights working out the bugs in my design so it should work fine for you. If something isn't working, I've found the top causes to be:
1. Solder shorts
2. unsoldered pins
3. backwards and incorrect parts
4. debris or bits of wire on the board
5. bad connector/wire connections
If you have a scope, it's pretty easy to trace the route a signal takes, and note where it stops (or gets messed up or whatever). With just a multimeter you can still do some testing, such as making sure the chips are getting power, and checking DC voltage levels where appropriate.
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