GPG

How many digits/resolution? What type of output, BCD, LED, LCD?

The diode is protecting the auto black level sense transistor. Any low current high speed diode rated at ~200V will do.

What is this diode's function

They will all work in this circuit. The layout is far more important

ICL7107 Power Supplies From the data sheet: The ICL7107 is designed to work from

Have you seen the one in our projects section? http://www.electronics-lab.com/projects/motor_light/037/index.html Does not look like it will take much modification to fit your needs. Spark tansmiters were more honest. You can do it with a cheap cordless doorbell

Be sure to google 74LSxxx. Or HC etc.

This can reach 2.5A

Q2 will supply current to the regulator (until it smokes)

Yes

If the zener reads low both ways it is :'( You say "I found the zener to be a 8.5v approx 1.5 A " How did you test it?. If it has some writing on it tell us, and the values of the resistors

The zener is the reference for the regulator. When the voltage on the base of the transistor exceeds the zener voltage plus Vbe, the transistor conducts tending to remove base drive from the pass transistor. So the regulated output is (Vz + Vbe)*(1+R1/R2) What are the original values?

Attachment did not attach so its here http://homepages.slingshot.co.nz/~peg/

The zener is the reference for the regulator. MJE800 is a darlington transistor http://www.fairchildsemi.com/ds/MJ/MJE803.pdf Does that make it look like the att. The unlabelled resistors are part of the darlington.

It is possible to use the drop across your existing wiring to measure the current. The way I have done it is to use a magnetic field sensor like this: http://www.allegromicro.com/sf/0750/ I rolled my own using a sensor and a modfied rectangular ferrite core salvaged from an old tv line drive transformer The pot you have suggested remembers the last setting. How many channels do you need to control