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Taito Asuka and Asuka Repair [In progress]

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xodaraP

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Hi all,
I have a Taito Aska & Aska that boots to a garbage screen and no further.

The RGB0070 is loose but not yet broken off (Edit: it broke off when I turned the board upside down to remove an IC)

I noticed that the RESET and HALT lines are asserted, but the reset is moving slightly. I checked the TC0220IOC (@caius has found that reset line issues are often this chip) and the RESET output on pin 8 is working. But the board is stuck in watchdog.

Moving from the TC0220IOC the signals are sent to the CPU via a LS07. Input is correct but output appears to be wrong.

All I'm getting is a very weak signal to the CPU for reset, but I did notice this line is pulled down by a resistor. I'm not sure why there are resistors on the output to the CPU.

My desoldering gun isn't working correctly but next step is to remove and test the LS07 off board and replace if necessary. I also need to build and install a RGB0070 repro board.
 
@caius - can you confirm if the bad TC0220IOC gives no/stuck reset output at all from pin 8? I don't want to pull out the LS07 only to find that it's the custom after all.

I'm getting no data movement at all. It's literally just watchdog resetting. I did notice the 68k is getting really hot, but assumed this was due to the constant resetting.
 
There is a good amount of info about this custom IC.Anyway, you will have a reproduction in some time, stay tuned!
 
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I replaced the custom IC and I have the same issue. The custom IC is not at fault sadly :(

I even installed the Asuka and Asuka custom back onto the board I removed the replacement from to test it and it worked there.

Good news that the custom isn't dead, bad news that it's something else
 
If the board is still watchdogging then you have some trouble in 68000 code execution, this can have different causes (broken traces, bad RAMs, bad logics , etc..)
 
I've tested the main program ROMs and they're good. Currently installing a repro TC0070RGB custom.

RAM signals look good. I'm wondering what else is on the reset circuit.
 
I had several of the Macro repro boards made quite a while ago to fix an Operation Thunderbolt for someone and still had spares so I built one of those. Another friend sells kits so he sent me one of those too.

Yours are nicer but given the current situation of world shipping it would probably never get here :(

My desoldering gun died for the second time in a month when I was clearing the holes for the custom so I'm now waiting for a replacement.
 
Ok so moving on (RGB custom isn't installed yet but I can still move onto other areas that might be the cause)

The 6264 SRAMs below the custom I assume are sprite or palette RAM are getting absolutely roasting hot, as is the 68k.

Maybe a short somewhere?
 
They are the palette RAMs, you can easily figure out this by checking the data line as they are connected to the 'TC007'RGB' DAC.
 
Indeed. I will reinstate the RGB custom and see if I get anything different since I'm assuming the TC0220IOC custom expects inputs from everything connected to it before it allows the board to continue the boot sequence

I'm getting no activity on the main CPU ROMs at all. So something is definitely unhappy.
 
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