Meters are up and running!
I've been on the stump, trying to find some resistors in town. Living in a small town makes it hard to find a 9.90 megohm resistors, but I got the mission accomplished. To get the meters to read the proper range, resistor RB needed to be taken out and replaced with a 9.90megohm resistor, which I made from 2 4.7M and 5 100Ks. Then RA needs to have a 100K ohm resistor in parallel with the existing resistor. The manual says to use .1%, I used 5% and got the values that I wanted.
Here are a couple of photos of the guts and the unit working. I put in a power switch and LED for power, another switch to take the hot lead off the Ultravalve bias pots and I even put in a power receptacle in case I want to put a 10 gauge power cord to it from my 9 volt, 500ma wall wart!
Here is a bill of materials if any of you would like to build one:
(2) Test lead sets Parts Express #390-120
(1) 2.5mm Panel Mt DC Jack Parts Express #090-479 (this may change depending on wall wart)
(1) 9 volt wall wart (go to Radio Shack and get one) Parts Express measured 14.6 volts
(2) Dual binding post Parts Express #090-475
(2) Velleman meters Parts Express #320-241
(1) Box Radio Shack size: 6 X 4 X 2
You will need to cut a couple of rectagular holes for the meters as they need that to mount (snap in).
(2) 100K 1/4 watt 5% resistors
(2) 9.90M 1/4 watt 5% resistors (or (4) 4.7M + (10) 100K ohm resistors (as I had to do).
If you build the resistor series network, get a couple of breadboards (Radio Shack #276-148).
(4) rubber stick on feet (Radio Shack #64-2342, pkg of
(2) Double pole, double throw switches.
(1) Red Led, 2 volt, 20ma.
(1) LED panel mount escutcheon.
(2) Feet of Cat-5e wire (stripped and untwisted) to make interconnect wire.
I will make a schematic later.
Also notice the wiring. That is exactly why Frank has me do mechanical.
Wayner
