Qix main board - no acid damage but not working

texasmame

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I have a complete working set now so I can say all voltages good, all socketed chips known good, ribbon cables known good.

On this problem, acid-free main board shows 1 and 3 LEDs lit and nothing happens when you push the self-test button on the board itself. If the CPU is removed, the results are the same so the LEDs are not showing any legit self-test results.

I have replaced the sockets for the CPU, the 6845 and the 2114 RAM (U2 and U3), cleaned and reflowed headers with all new solder as well.

The test points are as follows which are all the same as on a working PCB with the exception of TP1 which starts high then goes low (INVERT signal).

1 = high w/ "chatter"
2 through 5 = pulse
6 = low
7 = high
8 = high

Summary: there's clock and input and output where there should be on the CPU and the 6845, even the 4116 are pulsing, but nothing on screen and can't even start self-test (yes, self-test switch tests good).
 

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Check that reset circuit is working & getting to all 3 boards.

Does the CPU act like a 16 bit counter when you ground the points mentioned in your screenshot? You should be able to follow those signals to the ROMs themselves if I remember correctly.

Disclaimer, I shelved my Qix project that was in a similar state as yours and haven't been back to revisit it in a while. My boards have alkaline damage that I tried repairing so I'm sure I've got either trace or socket damage that still needs addressed on mine.

Knowing which order the chips are activated and the signals being sent back and forth between the 3 boards is part of what I still need to figure out.
 
Check that reset circuit is working & getting to all 3 boards.

Does the CPU act like a 16 bit counter when you ground the points mentioned in your screenshot? You should be able to follow those signals to the ROMs themselves if I remember correctly.

Disclaimer, I shelved my Qix project that was in a similar state as yours and haven't been back to revisit it in a while. My boards have alkaline damage that I tried repairing so I'm sure I've got either trace or socket damage that still needs addressed on mine.

Knowing which order the chips are activated and the signals being sent back and forth between the 3 boards is part of what I still need to figure out.
Wouldn't there be no signs of clock and other pulsing if the reset is never sent?

BTW, I've tried the manual reset at the CPU pin to no avail.
 
Clock is separate from reset, it's actually a prerequisite, (reset won't work without a clock signal) you'll have clock everywhere but it's the reset signal that tells all the CPUs when to sync up & begin working together. At some point in the startup process the 6845 will be programmed to output a video signal.

Qix/ZK boards get their master reset signal from the power PCB on an original setup, if you're using the arcade shop adapter + switcher on your test bench it's built into that adapter. /RESET should be held low temporarily then stay high after that.
 
I have a complete working set now so I can say all voltages good, all socketed chips known good, ribbon cables known good.

On this problem, acid-free main board shows 1 and 3 LEDs lit and nothing happens when you push the self-test button on the board itself. If the CPU is removed, the results are the same so the LEDs are not showing any legit self-test results.

I have replaced the sockets for the CPU, the 6845 and the 2114 RAM (U2 and U3), cleaned and reflowed headers with all new solder as well.

The test points are as follows which are all the same as on a working PCB with the exception of TP1 which starts high then goes low (INVERT signal).

1 = high w/ "chatter"
2 through 5 = pulse
6 = low
7 = high
8 = high

Summary: there's clock and input and output where there should be on the CPU and the 6845, even the 4116 are pulsing, but nothing on screen and can't even start self-test (yes, self-test switch tests good).
Anything on the screen at all?

Look at Pin 37 of each of the 6809's and see what they are doing. After system boot, they should be high.
 
Clock is separate from reset, it's actually a prerequisite, (reset won't work without a clock signal) you'll have clock everywhere but it's the reset signal that tells all the CPUs when to sync up & begin working together. At some point in the startup process the 6845 will be programmed to output a video signal.

Qix/ZK boards get their master reset signal from the power PCB on an original setup, if you're using the arcade shop adapter + switcher on your test bench it's built into that adapter. /RESET should be held low temporarily then stay high after that.
Yes, using an AS adapter/switcher. Working set still works properly with it.

On this set, comprised of known working ROM and sound PCBs and the problem main board, resets starting high and staying high on both boards. Even manual temporary grounding of RESET pin on CPU won't get 'em started.

Now, on the good board, the RESET signal also starts high and stays high, just like on the bad board, but the manual grounding/reset works on the good board set.
 
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Anything on the screen at all?

Look at Pin 37 of each of the 6809's and see what they are doing. After system boot, they should be high.
Nothing on screen.

All are starting and remaining high, even on good boardset. So, presuming they are low just prior to the 5v getting to the logic probe, at least on the good boardset.

Either way, the manual reset should work if it were just a reset issue.
 
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I have two that are doing pretty much the same thing - both acid free.

These are available for sale/trade if anyone wants them.

LMK, thanks for the effort!
 
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