Fixing a Chase HQ S.C.I PCB (Taito Z system)

[mypinballs]

Got a Chase HQ SCI pcb in recently to fix up. Love this game and want to run it on my chase hq upright as an alternative to the v1 game. This one I played more int he arcade is think back in the day.

The thing is dead, so looking about in case anyone has fixed these before or has suggestions. I have a clock pulse to the main 68000, main roms (4 of verify ok). Reset chip is working. Reset line to main 68000 is watchdogging. I am trying some replacement pals C09-25, C09-24 and C09-26.

Had a similar issue with the Sega golden axe 2 where the reset chip doesn't work unless you have a seriously powerful supply for 5v. Board is drawing about 3.3A when on at mo but nothing on screen

Any suggestions on what to check next would be appreciated if anyone has looked at these before

 

[mypinballs]

I am using the chase hq 1 schematics and they are ok, but things don't match exactly. On SCI we are using the terrible TC0220IOC instead of another suitably terrible one. I really have no idea why you would make a custom chip for I/O and not have some sort of protection for bad connections built into it. Seems these chip go bad a lot. Anyway I checked and the reset line output for the main 68000 is indeed fed from the TC0220IOC and the TC0220IOC seems to take the VBL clock and the normal reset line in from the normal reset chip to make the custom reset line output.

So I decided to remove the TC0220IOC and temporarily jumper the normal reset line to the 68000 and see what happens.

Still a blank screen but now I can see data and address on the main 68000 and main roms. I was kind of hoping the game might boot alittle way and do a ram test etc, but I guess Taito have some sort of check/initialise to the TC0220IOC first to see if its ok before anything is outputted on screen, STUPID!!!

So my next thing will be to change this chip, remove the temp jumper and see if I get any video output.

 

[mypinballs]

This arrived today! so we will see soon what we get

 

[caius]

You can't simply by-pass the TC0220IOC and route the /RESET signal to the CPU because this custom IC does more than generating the /RESET
Anyway, I'm working from time to time to reproduce this custom IC, I had figured out some of the functions but I think a decapping is needed to reveal the internal structure and therefore all its features.

 

[mypinballs]

You can't simply by-pass the TC0220IOC and route the /RESET signal to the CPU because this custom IC does more than generating the /RESET
Anyway, I'm working from time to time to reproduce this custom IC, I had figured out some of the functions but I think a decapping is needed to reveal the internal structure and therefore all its features.

If you want an old ic to disect or a new one let me know. I'm happy to help with the cause of trying to work out what these nasty chips do!! They are a massive pita!! Some understanding of what they do internally regarding the reset section would be very useful!

 

[mypinballs]

Update on my board. I am stuck and cannot get passed a watchdogging reset line I changed the TC0220IOC ic but it didn't cure the problem. I was hoping the reset part of the ic was simply to take a couple of inputs and then output a reset line if these were present but it seems its more complex than this. Frikin stupid design!

The only thing i get on screen is a bad sync screen as below

I scoped the clock signal which was ok to the cpu at 12mhz

The reset output from the tc0220 looks like this

Not good, but i guess it shows the tc0220 is working

The only other thing inputted for reset is this video signal. Im not sure if this is ok or not. Hard to determine from the bad schematics what this is from.

 

[kissedin]

Any progress? Just got a SCI with similar symptoms like yours (bad sync screen, board keeps resetting).

 

[mypinballs]

Any progress? Just got a SCI with similar symptoms like yours (bad sync screen, board keeps resetting).

Unfortunately not. My board is still broken. I think the biggest issue with these boards is general operator/user guy thinks its normal jamma when its not and plugs a std jamma hardness into the connector which fries loads of stuff.

 

[kissedin]

I got a cab from Electrocoin. Their power wiring is Jamma except that there is 13v instead of 12 on the solder side on the plug.

 

[oguzog]

I do have same board and already tried with jamma (hope i didn't fried anything).

How can i test this board? I only have jamma supergun nothing else.

 

[kissedin]

Mypinballs. We seem to have same symptom. Today I got my SCI to boot. Problem was a faulty TMM2063 which I think is used for the main program. That is why my board booted over and over, it read empty or corrupt data.

Have you tried to piggyback the RAMs at the main program ROMs?

(Still some graphical issues. I know one ROM is bad and is waiting for some new 27C400 to arrive. I'll eventually start a new thread for updates)