Dragon's Lair Fans - Arcade Lifestyle
General Chat => Technical Area => Topic started by: vernimark on December 01, 2015, 04:41:15 PM
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THis is what happened switching on the game
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THen, following the schematics I shorted J13 in order to have a good reset signal
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now I can see "something" but...
https://youtu.be/XAFgd3QXj7g
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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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do you suggest to replace all 2102?
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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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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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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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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...
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Video is private :)
Paul.
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Done :-)
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Still private :)
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Done done
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Looking much better. Seems almost there. That with a complete new set of both the video & program RAM?
Paul.
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Replaced 5 video rams.
My question is: what is the difference between 5101 and 2101?
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The 5101 is a CMOS RAM often used for battery backup. 2101 is a fast TTL RAM.
The 5101 has weaker drive and much slower timing than 2101. 2101 likely has more bus loading.
Paul.
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Ah. I ve to verify if i have both.
Could they be the cause of the reset?
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Possibly, yes - I'd replace with the right type and see.
Paul.
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10 rams replaced and continues to reset
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I can see removing EPROM in position 46 nothing changes
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A bad ROM or bad ROM decoder. There is not much to this hardware, really. It's very simple.
Paul.
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EPROM inolved is #5 (position 46). Its CRC is correct (bdae09fe), anyway I burned another one and nothing changed.
So I replaced the LS155 in position 41 (on my PCB is labaled 41/LS156) but nothing changed again.
Actually even if I proceeded quite well during the night now I've no idea what to check. probably the EPROM socked but I don't know what else. TTLs I tested seem to work.
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What type of EPROM is it?
Paul.
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2708
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There are some editions of The Invaders that use PROMS and do not have all the three supplies implemented on the power board to be able to drive a board populated with 2708. The effect of that is that the game doesn't run properly. Therefore, check you have +12, -5 & +5V on your power supply.
Paul.
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Of course i have. In fact my invaders has proms
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Grounding pin 6 of chip 7400 in position 12 cars run on the screen but collision are not detected.
I suspect 2101 i replaced is not working. That signal drives 5101_2101 RW
I have several 5101but only one 2101. I used a 5101 instead of the 2101 but nothing changed.
I replaced chips 11 12 13 24
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OK I make a break now.
Looking at the TV "Law & Order - Special Victims Unit" all night long I replaced almost everything on the board :lol: :lol: :lol: but nothing changed
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Possible ideas are that you have a bad ROM, missing video interrupt or stuck input. Could also be a bad power supply. ROM are RAM is the most statistically likely, however if you're sure they are good... ;)
Paul.
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I verified ROM crc multiple times.
I'll update you once I'll receive new 2101
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em.... I don't know how to say...
the behavior of my PCB is righ. running the game with mame I can see there isn't any attract mode and after few seconds the game redraw the maze ::)
this afternoon I'll test board in its cabinet
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Hehe :)
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https://youtu.be/Uqw3-dKDqBQ
Credits acelerator and start 2 work.
The rest will be fixed next week
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Nice, looks almost done now.
Paul.