Our Marvel SuperHero Zizzle 3/4 pinball machine would not power-on. After doing some poking around, it became clear that the 24v power supply brick was working, but there was no power going to the CPU/LED circuitry. Others had isolated similar problems to a small daughterboard with a custom chip designation. Looking at how the chip was wired in, some suggested it was a voltage regulator.
The chip in question was almost certainly a LM2576. Looking at the PCB and surrounding components, it is pretty clearly the same step-down voltage regulator circuit that shows up in LM2576 data sheets. Some of the capacitor values are different, but I’m assuming that’s mostly due to the amount of current they tried to use here. Based on the voltage divider resistors on the output leg (pin 5), this was setup to step down to 5v.
Instead of just replacing the one chip and possibly running into a similar problem down the road, I opted for a different solution. I purchased a 5A DC-DC adjustable voltage regulator module (at the time I wasn’t sure the logic ran at 5v or 3.3v). I then just removed the old add-on board, and wired in the new. I started off at 1.5v and slowly raised it to 3.3v. At 3.3v, almost everything worked except the LCD score display. After reviewing the circuits again, I decided to try 5v, and that solved the scoring issue.
Rather than trying to mount the new module (which is almost the same size as the old) into the same spot on the circuitboard, I opted to just attach to the inside of the pin using servo tape. It meant adding longer wires and a separate ground wire, but that wasn’t difficult at all.
After a few weeks of being 100% functional, our Zizzle is once more out of commission. The machine has both flippers stuck in the active position. The Zizzle has 4 coils (one for each flipper, one for the pops and one for the slings). The transistors powering the solenoids are 2SD882 NPN silicon power transistor (TO-126 form factor). Stats on the specific solenoids are:
Open Frame Solenoid SH-1253
| Duty Cycle | 100% | 50% | 25% | 10% |
|---|---|---|---|---|
| Power consumption | 6w | 12w | 24w | 60w |
| MAX on time | ∞ | 140 sec. | 50 sec. | 9 sec. |
Replacing the transistors has them blow again as soon as the flipper is activated again. I suspect there is either a problem with too much current being drawn by the flippers (but why the sudden change in both flippers), or a blown pull-down resistor (again, why both)??