Build Your Own Arcade Controls Forum

Arcade Collecting => Miscellaneous Arcade Talk => Topic started by: Scottacus on February 25, 2015, 10:03:52 am

Title: Gorf goes crazy on startup
Post by: Scottacus on February 25, 2015, 10:03:52 am

Here is a problem that I can't figure out and I wonder if anyone else has come across this one.  When I first apply power to the Gorf game it continuously cycles the coin meter a couple of times a second, displays the start up screen with two player scores on it and has choppy audio.  If I turn the power off momentarily and reapply power, everything starts up just fine so I have a work around if I can't fix this.

I recapped the power supply and get correct voltage out for all voltages except -5v which I can't get any closer than -5.1v to the -5v.  I read up on the Z80 cpu and it needs to see 0v to reset and then +5v to run.  My brother who is an EE looked at the linear power supply schematic and said that there is a timing RC circuit in there that looks like it does just that.  I only have a digital volt meter so I can't see this 0v pulse.  I also checked out the coin meter and it needs pulsed 9v to make it cycle so a pulse must be going down that wire.

Anyone ever see anything like this?  I have a different set of boards coming from an e-bay auction so I will try those out when they come.

Title: Re: Gorf goes crazy on startup
Post by: SavannahLion on February 26, 2015, 04:51:22 pm

http://forums.arcade-museum.com/showthread.php?t=337536 (http://forums.arcade-museum.com/showthread.php?t=337536)
 :dunno

Title: Re: Gorf goes crazy on startup
Post by: Scottacus on February 26, 2015, 05:18:15 pm

Everything seems to keep coming back to the 0066-117xx chip doesn't it?  It is interesting that my test screen also shows an "X" on it...

Thanks for finding this!

Title: Re: Gorf goes crazy on startup
Post by: Scottacus on March 02, 2015, 10:08:48 pm

New (old) CPU board and now no crazy coin counter.  Hope this helps someone in the future.