Zaccaria/Seevend/NSM-Lowen Zaxxon Maintenance 2019

30/05/2019 - Northwest Pinball and Arcade Show (2019)

Zaccaria games at NWPAS Dead zone at NWPAS

The game was running OK for the first few days of the show but by Sunday it was no longer booting with no video sync. Initial triage found the +5V output from the power regulator PCB at 3.36V and the AC power connector into the power brick had charred pins. The game was withdrawn into the dead zone for the remainder of the show :(

08/08/2019 - Power brick pin repair

Power assembly Initial power reading Power brick plug

The +5V at the regulator PCB output measured 4.46V and I'd already noticed the charred power brick plug at the show. Other symptoms of power issues were that the regulator PCB connectors were already hot after a few minutes and the transformer was rattling so much it had shaken loose all its mounting bolts and was "sanding" the top of the frame (!)

Power brick, underside Power pin replacement Power pin replacement

Replacing the female pin in the power brick was straight forward. A jewelers screw driver was used to push in the springs so the pin could be pulled out, cut off and a new pin fitted.

09/08/2019 - Power brick cleaning

Power brick, top, cleaned

Cleaning the top of the power brick revealed the root cause of all the power problems on this game - the Zaxxon game PCB draws more +5V current than the cabinet power supply was designed for. The manual shows the linear regulator rated at 4A and the connectors, cabling & fuse rated at 5A. In this cabinet the distributor had replaced the 11V AC 5A fuse with 6.25A according to the neat label on the brick. Increasing the fuse value and a nice label doesn't change the design of the power supply :|

13/08/2019 - Power connector repair

Power brick connector pin repair Power regulator connector pin repair Power regulation PCB pin cleaning

The replacement of the power brick and regulator connector pins followed the same procedure - a jewelers screw driver to depress the pin spring and release the pin from the housing, cut and replace with a new pin. The regulation PCB pins are straight forward to clean with a wire brush at the expense of snapping off the top cover to get at them.

13/08/2019 - Cabinet cleaning

Cabinet base cleaning

Whilst most of the power assembly was out of the cabinet I took the opportunity to vacuum & clean the cabinet bottom.

14/08/2019 - Re-test

Power assembly, reinstalled Zaxxon, not booting

After all the AC side power repairs the game PCB still wasn't booting in the cabinet but ran without issue on the bench. Checking the power voltage along the chain:

It did look like the AC side power repairs resulted in a healthy +5V DC at the power regulation PCB output but 0.44V was lost by the time it got onto the game PCB. By far the biggest loss was the single 5V cable connecting the power regulator PCB to the first Konami edge connector. The cabinet has two separate ground cables & connector pins but only one 5V supply cable that appeared to be dropping 0.26V. I was little surprised but a direct meter measurement confirmed that there was 0.29V across the +5V cable.

16/08/2019 - 2nd power cable

5V DC power pin, original 5V DC power pin replacement and 2nd cable 2nd 5V DC cable assembly

The plan was to wire in a new connector pin along with a second thick gauge wire through to the Konami edge connector. Since the Konami standard pinout only has two +5V edge pins the existing split was separated to allow one wire to feed each finger. With the new connector pin & second power cable the voltage at the game PCB was up to 4.71V (from 4.56V) but the game still wasn't booting in the cabinet :(

17/08/2019 - 2nd power smoothing capacitor

5V DC ripple 2nd 10,000uF smoothing capacitor Zaxxon running OK

The next step was to look at AC ripple. In AC mode the meter read 0.69V AC ripple on the +5V line. Looking on the scope confirmed very high ripple from ~3.5V to ~4.5V at the game PCB. Given that the linear regulator was being run at maximum and had already had a cap kit fitted recently I suspected that the modern replacement 10,000uF smoothing capacitor was likely more accurate and lower than the original had been. The 1B1126 regulator PCB had more than enough space to accommodate a second 10,000uF capacitor side-by-side in parallel with the first for a 20,000uF total. With that fitted the +5V DC measured 5.02V at the game PCB and finally the game booted & ran OK in the cabinet.

Zaxxon power assembly, rebuild complete Zaxxon running OK

The power assembly was reinstalled back into the cabinet and the game run for several hours to confirm power distribution was stable and didn't burn up again. There were two minor issues that I left as is for now - there was a slow moving dim vertical band that crawled slowly across the screen and audio had noticeable background hum. Neither was seemed to be significant enough distractions to be worth investigating yet.