BryanMcPhail.com

Professional software development, amateur BMW tinkering, old arcade game stuff

Jul
2

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Rastan PCB repair

Category: Arcade Tags: , , Leave a Comment

Ok, calling this is a ‘repair’ is probably a misrepresentation as it was so easy. I bought this pcb from a junk pile and it arrived a bit dusty but not physically damaged in any way. It was missing all eproms (68K program, Z80 audio program, audio samples eprom) and the socketed PAL at IC58 (PAL16L8). The schematics show that IC58 generates monitor sync so it definitely wasn’t going to show anything without that..

Burned all eproms from the MAME set, and the PAL16L8 onto a GAL with thanks to the PLD images at http://www.jammarcade.net/pal-dumps/

And it worked! Well, almost – no sound and wouldn’t accept any coins. It seems this is due to the connector marked H on the board. I’d assumed this was a stereo sound output, but it seems 12V is required here in order to power the sound amp and coin IO. 12V from the jamma connector already runs here – so you have to jumper pins 1 & 2 together and 3 & 4 together to enable sound & coins. With this done the game worked fine.

Mystery 1 – why does connector H even exist, when 12V is already at the jamma connector!?
Mystery 2 – why did an operator strip a (presumably) working board just for some cheap eproms and a PAL? I guess something else more important at the time needed the parts.

Oct
21

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Wells Gardner K4900 monitor fix

Category: Arcade Tags: , , Leave a Comment

This JAMMA cabinet had gone pop almost two years ago, time to diagnose why. On applying power the primary fault was quickly identified – high voltage fireworks were literally shooting out the top of the flyback! You can see the burn marks on the picture, but there is probably a hairline crack as well.

So, remove old flyback, install new one… and it worked! Great to find the fault hadn’t taken out anything else on the board. Usually this would be a good time to install a cap kit, but it seems the previous owner must have done this at some point, as all the caps looked new. (Disclaimer, do not attempt to remove or even touch the flyback or tube if you don’t understand how to safely discharge a CRT. Very high voltages can be present even with power off).

Apart from some screen burn in, picture quality is great for a 33 year old monitor!