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Author Topic: DODGEM PCB troubleshooting  (Read 14980 times)

vernimark

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DODGEM PCB troubleshooting
« on: December 01, 2015, 04:41:15 PM »
THis is what happened switching on the game
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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #1 on: December 01, 2015, 04:42:46 PM »
THen, following the schematics I shorted J13 in order to have a good reset signal

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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #2 on: December 01, 2015, 04:45:59 PM »
now I can see "something" but...

https://youtu.be/XAFgd3QXj7g
« Last Edit: December 02, 2015, 10:36:46 AM by vernimark »
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PaulSwan

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Re: DODGEM PCB troubleshooting
« Reply #3 on: December 01, 2015, 06:03:50 PM »
The bitmap RAM on this game is not readable and thus the game runs even if it's bad. Not sure if that's your only issue, however :(
Paul.
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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #4 on: December 01, 2015, 06:15:59 PM »
do you suggest to replace all 2102?
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PaulSwan

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Re: DODGEM PCB troubleshooting
« Reply #5 on: December 01, 2015, 06:45:40 PM »
If it were me, I'd use a tester to write specific patterns into the bits and then check the output to see which bits (and thus which RAMS) were bad. But you'd need either my Arduino tester, a Fluke with a Z80 pod and 2650 adaptor or to write your own test ROM to do that :)

It also looks like you may have some other issues since you're seeing whole characters all over the place that suggest a program ROM or RAM issue.

If you decide to invest in an Arduino tester, there is a guy on UKVAC who's done a run of 10 PCB's and thus has a lot of spares available. I haven't added support for Dodgem/Invaders to it yet, but I'll try and make a start on that over the Xmas break.

Paul.




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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #6 on: December 01, 2015, 07:20:11 PM »
wow, I'll think about that. Could be the time to improve my tools  ::)

anyway I changed both CPUs and checked the ROMs. This is all I could do.

Tonight I'll try something else
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xadhoom

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Re: DODGEM PCB troubleshooting
« Reply #7 on: December 01, 2015, 08:57:29 PM »
Nice work marco. Is that the board on the cab that i take for you?
I'm also interested in that Arduino tool!!!
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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #8 on: December 01, 2015, 11:34:18 PM »
Yes it is.

Replacing some RAMs  i  can say i m on the right way

https://youtu.be/V-kJ4W3wqtw

I dunno why it resets...
« Last Edit: December 02, 2015, 10:39:22 AM by vernimark »
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PaulSwan

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Re: DODGEM PCB troubleshooting
« Reply #9 on: December 01, 2015, 11:43:17 PM »
Video is private :)
Paul.
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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #10 on: December 01, 2015, 11:57:50 PM »
Done :-)
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PaulSwan

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Re: DODGEM PCB troubleshooting
« Reply #11 on: December 01, 2015, 11:59:58 PM »
Still private :)
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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #12 on: December 02, 2015, 12:14:19 AM »
Done done
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PaulSwan

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Re: DODGEM PCB troubleshooting
« Reply #13 on: December 02, 2015, 12:16:47 AM »
Looking much better. Seems almost there. That with a complete new set of both the video & program RAM?
Paul.
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vernimark

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Re: DODGEM PCB troubleshooting
« Reply #14 on: December 02, 2015, 12:19:45 AM »
Replaced 5 video rams.
My question is: what is the difference between  5101 and 2101?
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