To cascade rings, “Pulse Out” can be taken from the lamp side of any of the 11K resistors which are tied to ground. It must not be loaded too heavily by the successive stage or its operation will be effected. One important thing to remember — as far as the overall clock is considered — the stage which is used for “Pulse Out” will be 0 for that ring. This is most important for the minutes and 10s of minutes rings.
First, a warning! This clock uses 120 volts and 160 volts which are present throughout the board. Handle the board carefully! The corners are “ground” and the board can be held by them safely.
This board contains parts which must be installed in a certain direction. The electrolytic capacitors must have the positive lead (typically, the long lead) inserted into the hole with the square pad. There is a small plus sign by that pad, as well. Diodes must have their cathode inserted in the square hole. The cathode side of the diode has a stripe painted on it. The transistors and the regulator have their outline silkscreened on the board. Be sure to orient them correctly. The markings on the bridge rectifier are faint, but they match the markings on the silkscreen of the board. Pin 1 of the two integrated circuits has a square pad. Putting in any of the parts backwards will cause the clock to malfunction or damage to occur to the component or the clock.
I do not recommend using water soluble rosin core solder, either. My attempt at building one of these clocks with it just left me totally frustrated. The water soluble rosin is conductive and you need to wash the board, then dry it completely to test the clock as you build it. Any changes to parts of the rings involve a wash and dry cycle, as well.
■ FIGURE 6. Completed Circuit Board.
board upside down and solder them in on the solder side. Once they have cooled, the board can be moved freely.
Next, the power supplies should be built; first, the low voltage portion, making sure that 12 volts (may be as high as 15 or 16 volts) and five volts are made. Then, build the high voltage portion. Make sure that it generates about 160 volts. Adjust R3 until it does. About 120 volts should be present on the cathode of Z1.
Next, the miscellaneous parts which have small quantities should be installed. These include the 51K, 100K, 1M, 470K, and 220K resistors. Follow these with the 20 pf, .01 µF, .1 µF, and the 150 µF capacitors. Once these are installed, install the MPSA42 transistors and the four colored neon bulbs which are a frosted white color when unlit.
Next, install the three micro switches, the socket for the CPU, 16 MHz crystal, two 1K resistors, and the J2 header. DO NOT INSTALL THE PROCESSOR YET.
Now we start work on building the ring counters themselves. One at a time starting with the bottom center ring counter, work your way around the board clockwise. We need to test each ring before moving to the next.
In an ideal world, the neon bulbs would have identical firing voltages. Sadly, they do not. After building a number of these clocks, I have found that most of them will only have one or two bulbs which don’t want to work right. Other clocks have had five or six lamps misbehave.