Zaccaria / Cinematronics Space Pirate credit PCB repair log

[IZ8DWF]

Hi all!

I'm back with a whole load of arcade stuff I received. It's all vector stuff this time, including monitor PCBs. The games are all old Cinematronics (star castle, rip off) and their italian Zaccaria clones (space fortress, space pirate).

I'm starting with the Zaccaria space pirate which is a clone of Cinematronics' rip off. The logic PCB is marked Cinematronics, though the audio PCB and the credit PCB have zaccaria markings, so I assume it was an official clone(?).

However, the Zaccaria clone has two major differences: the video DACs are located on the audio PCB (on the real Cinematronics vector games, the video DACs are on the,  monitor PCB) and there's an additional PCB installed between the coin inputs and coin counters and the logic PCB. The only function of this PCB is to allow dual coin inputs instead of the single one of the logic PCB and larger choice of coin to credit options with different settings for coin inputs 1 and 2. I guess it was easier for them rather than changing the code on the logic PCB.

The logic PCB by the way doesn't have an integrated CPU, it is instead made with 3 TTL ALUs a bunch of TTL PROMs and a whole lot of TTL glue logic. I guess in 1980 that was much cheaper than buying one CPU for each game board.

If you happen to be working on the Zaccaria clones, get the Space Fortress pdf manual: https://www.progettosnaps.net/manuals/pdf/spaceftr.pdf as the hardware is the same but the scan quality is a bit better than the Space Pirate manual.

Now the actual fault: the first board would not take credits. If you don't have all the original cabinet wiring harness (I don't), it's much easier to first debug the little credit PCB and then work on the logic/audio boards together (remember that the audio board has also the video XYZ outputs).

As we can see, the credit PCB only needs 5V and two switches to be tested. The 6.3V AC is just routed to the other connector for the cabinet lamps, so it's not required for testing.

First inspection of the board is always a diode and transistor junctions test with a multimeter, nothing bad was found. Then I checked the electrolytics' ESR and one of them showed very high ESR (> 20 ohms).

It was C7, the timing capacitor for the 555 based clock oscillator. The actual part was a 330nF 35V tantalum capacitor and not 1uF as reported on the schematic. I have used a 330nF 50V film capacitor as a replacement, there is no reason to use a tantalum capacitor there if not for space reasons. A 50V or 63V film capacitor (not a too ancient one) will fit perfectly in place of the old tantalum capacitor.

Having found no other issues, I wired the 5V supply and an old mouse button dip switch as the coin input 1. The common pin on the switch goes to ground, NC to pin 12 and NO to pin 13. Initially, when manually clicking on the switch I had no output toggling on the two NO and NC pins that go to the logic board (and no toggling on the counters' outputs too). However, as I was trying to understand how this circuit works, I realized that both coin 1 and coin 2 switch inputs must have the NC pin grounded. It's not possible to leave one coin input unconnected. As soon as I grounded also pin 10 (the other switch NC pin), the circuit started to produce the proper "credit" pulses on the outputs. I've verified that both the coin inputs can have different settings.

Now I don't yet know if the credit issue was due to the degraded capacitor or else. But having verified that the credit PCB works as intended means I don't need to have it connected to the logic board, I can simply use a dip switch to "coin" the logic board and simplify the test setup.

I will add replies to this topic as the repair proceeds.

HTH

Frank IZ8DWF