J99 power-up adjustments

[dkatz42]

I've just powered up my first J99 (no smoke!) and I'm not sure what to do next. The instructions are a bit, well, "terse" on this point. I managed to figure out (having powered up my first A12 ten minutes earlier) that the two pots adjust the voltage supplied to the 990Cs. They spec at 12-24v, so what should I set the voltage to? Any other adjustments to do?

Thanks...

[tpryan]

As you've realized, you're way out in front of the posted directions. The stuff on the site at the moment applies to the old board, which didn't have adjustment pots for the regulators. If you're using Hardy 990c op-amps, there's no reason you can't run them at +/-24V. If you don't need that much headroom, you can run them a little cooler with no problem, say +/-20V.

Before installing the big op-amps, check for -12V pin 4 and +12V at pin 8 of U3. Any reading within +/-0.5V is fine.

Once the op-amps are installed and the board is powered up, you can check for proper operation of the servos by measuring DC voltage at the output of the second op-amp. No-signal voltages should be below 3mV, usually less than 1mV.

[dkatz42]

Cool. They were at about 20V out of the box, and it sounded good to me. I'll check the rest, but it seems to be working.

I'm three-for-three now; I got an N72 running as well. I caught a backwards diode before applying power. Very interesting getting it out of there!

[chikkenguy]

what are the specific differences between different opamp voltages? more headroom at higher voltages and anything else? is there any reason not to run it as high as possible, say at 23 or 24 volts?

[chikkenguy]

what are the specific differences between different opamp voltages? more headroom at higher voltages and anything else? is there any reason not to run it as high as possible, say at 23 or 24 volts?