Final calibration check

[Unregistered]

Hi Carl and others
Have built the HH opt 2 and wish to know if there is way to calibrate and adjust R18 and R23 again after all is constructed just to check settings, rather than disconnect certain components.
Thankyou
george

[Rob in KS]

Here is what I did.
I had extra 4066s so I took one and bent pins 13 and 5 out so that they don't go into the dip socket. Then I soldered a piece of wire to short those two pins to pin14 (Vcc). This turns on both of the gates in the 4066 so you can balance the integrator.

Double check the pin numbers, I don't have the schematic in front of me.

Hope this helps

[Carl-NC]

If your IC's are not socketed, then there are 2 possibilities. You can short the sampling switches (IC7a/b) by shorting pins 1<->2 and 3<->4. This won't hurt anything even though everything else is running. An alternative is to shut down Q8 & Q9 by shorting their bases to -5D. That way the 74221 can't turn them on, and the IC7a/b switches stay on through pull-up resistors R44 & R48.

Once you have the switches turned on or shorted, remove the coil and adjust R18 to get some reasonable DC voltage on TP4. Then adjust R23 to get ~0V on TP5. Then adjust R18 to get TP4 back to ~0V.

- Carl

[Unregistered]

Thanks Carl n Rob will try that
george