Atari Liberator Reset line pulsing

i86time

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I have an Atari Liberator board with a pulsing /RESET line. The /RESET signal comes from pin 12 of the LS197 @ J11, fed by the watchdog & power-on reset circuits and some other inputs. I have verified that both the watchdog output (pin 3 of L4) and the power-on reset output (pin 1 of K12) go high as expected. 3 of the 4 inputs are tied to ground and 1 to +5v.

I could tell the LS197 had been previously been pulled and maybe replaced. I pulled it to test just in case but it tested OK. I even piggybacked it onto a working board with the /RESET pin bent out and it was held high as would be expected, so I'm sticking with the chip being OK.

This lead me to believe the 128V signal on pin 8 is the cause. However looking at it with a scope, it didn't look much different than that on my working board. There was some noise (a slight 'fluttering' on the trace of the waveform) but the peak and frequency was the same. Since the Liberator schematics had signatures, I used my analyzer and found all sigs for the LS163 @ H8 (which feeds J8) and the LS163 @ J8 (which creates the 128V signal) matched. Side note... I though the signatures published in Atari schematics were only for a CatBox and would not match standalone analyzers. However my HP5006A displayed the listed sigs exactly.

So if the 128V signal is good, the watchdog and power-on reset are good and the chip itself is OK, what else could it be? I thought it could possibly be another chip feeding back on the line, but when I bend out pin 12 and power on, the /RESET line is dead (neither hi nor low), so that's the source of the signal.
 

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Side note... I though the signatures published in Atari schematics were only for a CatBox and would not match standalone analyzers. However my HP5006A displayed the listed sigs exactly.
Plug in the Fluke 9010a w/a 6502 pod and check it out!?

How is the HP-5004A/5006-A sig analyzer compared against the fluke?
 
Plug in the Fluke 9010a w/a 6502 pod and check it out!?

How is the HP-5004A/5006-A sig analyzer compared against the fluke?

Unfortunately I don't have a 9010a. I don't think there's anything wrong w/ the HP5006A as I used it on a Battlezone and the sigs matched to that. I wonder if there is a possibility that a signature can match but there still be an issue with the signal that would cause a circuit not to operate properly. It seems unlikely but I can't figure what the deal is with this.
 
Maybe something else tied to /reset causing it. I'd bend J11 pin 12 out and see if there's still a signal on the /reset line.
 
I can finally close this out. The other week I was going over all of the signatures and found two PROMs where good data was going in, but bad sigs were coming out. Received two new ones from Steph, but the game still wouldn't play. Those good PROMs cleared up the last pathway in the signatures that were bad and I tracked the issue down to 4 data bus lines with junk on them. Turned out to be a bad LS244 buffer @ T9 in the bit map section screwing everything up.
 
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