Powering Galaxian PCB from switcher

Vraz

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I picked up an old Galaxian cabinet this morning, pretty complete but in need of some relatively serious TLC. The prior owner was planning to restore, but never got around to it (and his wife wanted it gone).

As a first step, I wanted to try out the PCB on my bench and see if it works and/or can be fixed. For powering from a switcher for testing/debugging, do I need to jump D4/D5/R87 or can I get away with just increasing the switcher voltage to help offset the voltage drop from the diodes? Seems like folks are selling adapters with no reference to jumping those parts which is why its unclear whether its required or not. Also, have seen two different pinouts for DC use, one which connects E/5 to +5 and one which leaves them unconnected-- does it matter (at least for testing)?

The board itself looks pretty good (especially considering the age) so I would prefer to avoid non-critical changes until I figure out a long-term plan. Thanks!
 
I asked pretty much the same question about my Pac-man board in this thread and ended up answering my own question: http://forums.arcade-museum.com/showthread.php?t=101875

My understanding is that either will work fine: a) don't connect E/5 but increase the 5V to ~5.7V to compensate for the diodes or b) connect E/5 to the 5V, effectively jumpering the diodes. I haven't actually connected my PCB yet though (need to rewire the harness), so if you do this and let out some magic smoke from your board, please let me know. :)
 
The answer to both of your questions has been posted many times. There is no need to increase any voltage coming from the switching power supply. Simply put just hook it up and go, no magic smoke included.
 
My understanding is that either will work fine: a) don't connect E/5 but increase the 5V to ~5.7V to compensate for the diodes or b) connect E/5 to the 5V, effectively jumpering the diodes. I haven't actually connected my PCB yet though (need to rewire the harness), so if you do this and let out some magic smoke from your board, please let me know.
I went ahead and connected including E/5 (with no on-board jumpers) and adjusted the PS until reading 5.05 on the board. No magic smoke released and after some repairs, the board is running fine.

The answer to both of your questions has been posted many times
Yep-- I had not searched under "Pac-Man Switcher" as I was focused on the Galaxian part without considering its more common cousins. While there are some threads under Galaxians, they are much less definitive (and one even says that powering it with the jumpers will damage components-- no idea if its true as there was no underlying technical explanation).

In any case, I connected with all the expected pins including 5/E but did not attach jumpers. The board did not fire up and had to do some troubleshooting. Clock was pulsing but CPU reset was always low. Found that POR was also low and went back to the video signal generator (which drives much of the timing). Turns out the LS161 at 4A which generates 32H-256H was dead (no output pulses). Removed the old chip, added a socket, put in a new chip and the board fired right up. Its been happily running on the test bench for the past 30 minutes. Something is wrong with the sound as I am getting mostly static, so need to track that down, but at least its mostly working.
 
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