Cap'n America schematics/tech info?

TonyG123

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Hey gang, I have a cap'n america (legit dataeast board) which isn't booting. Red LED is on, power checks out and I hear a quiet tone. (amp looks to be alive) - but no boot.

Reflowed one of the big ASICs as I saw some pins were bent.. otherwise board looks clean, nothing obvious missing, etc.

Looking for full schemaitcs - or at least can someone tell me where the CPU is on this board? I read that it uses an arm chip and also a Hu6280 (woohoo! PC Engine) but am guessing it boots from the Arm.

Thanks!
 
I can tell you everything about this board, except why it's not working most likely, as I've got 4 of the damn things on my to-do pile all stone dead..


The ARM CPU is the 101 chip at the top right corner. The 4 chips to the top and right side are the data bus latches. The address bus latches to the 3 chips in the lower right. It's a 32 bit CPU so there are 2 sets of 4 ROMs and 1 set of 4 RAM chips in parallel making up the main RAM. All the graphics hardware is 16 bit though, so the palette, sprites, tilemap interfaces all hang off the bottom 16 bits of the bus only.

The hardware won't put out any graphics signal at all unless the ARM initializes the tilemap chips. The jamma sync signal ultimately comes from the custom ASIC marked 56 (tilemaps). So anything interfering with the CPU writing to that chip will show as a dead board.

A bad sprite ASIC (71) could also lead to a dead board as the CPU waits for it to respond at boot, and I suspect a bad protection chip (75?) would do the same thing.

When I can work up the energy to get back to these things my next step is probably to write a diagnostic CPU ROM that doesn't get hung up on sprites or IO or bad ram and immediately tries to setup the graphics.
 
I can tell you everything about this board, except why it's not working most likely, as I've got 4 of the damn things on my to-do pile all stone dead..


The ARM CPU is the 101 chip at the top right corner. The 4 chips to the top and right side are the data bus latches. The address bus latches to the 3 chips in the lower right. It's a 32 bit CPU so there are 2 sets of 4 ROMs and 1 set of 4 RAM chips in parallel making up the main RAM. All the graphics hardware is 16 bit though, so the palette, sprites, tilemap interfaces all hang off the bottom 16 bits of the bus only.

The hardware won't put out any graphics signal at all unless the ARM initializes the tilemap chips. The jamma sync signal ultimately comes from the custom ASIC marked 56 (tilemaps). So anything interfering with the CPU writing to that chip will show as a dead board.

A bad sprite ASIC (71) could also lead to a dead board as the CPU waits for it to respond at boot, and I suspect a bad protection chip (75?) would do the same thing.

When I can work up the energy to get back to these things my next step is probably to write a diagnostic CPU ROM that doesn't get hung up on sprites or IO or bad ram and immediately tries to setup the graphics.
Thank you very much for this info - definitely gives me some things to start checking with the scope at least. There's no source for the ASICs right?
 
I'm in the same boat with a dead Captain America (Data East board). Seems like a whole load of problems that can stop it booting.

Always start with the easy stuff, power supply voltages, connections, and fuse holders. Then move up to clocks, verify CPU clocks and all other CPU control lines, address lines and data lines. Make sure ROMs have correct programming.
Test mode can provide some clues but if clocks are missing = dead board...
 
Managed to fix my board. It had a dead 74F245 in the CPU section (position 2D going by the edge markings on the board). If yours has one of these SMD logic chips dead make sure you get the 5.30mm width and not the 7.50mm width. Hopefully you can get yours fixed as well. Good luck :)
 
Checked it over with my scope. Would have shown up with a logic probe as well though as the A side of the bus was completely dead, just had my scope set up on my bench and my probe was tucked away in a drawer.

Strange thing was I've had this on my repair pile for a while now and only looked at it again when I came across this thread and your helpful info :)
 
When I can work up the energy to get back to these things my next step is probably to write a diagnostic CPU ROM that doesn't get hung up on sprites or IO or bad ram and immediately tries to setup the graphics.

Just got a dead Captain America and found this thread. Any luck with the diagnostic ROM?
 
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