5/2/2010 Battlezone won't boot, keeps 'watchdogging'. Does not give any error beeps and will not boot into test mode. Disabling the watchdog by using an alligator clip jumper between the 'gnd' and 'wd dis' headers results in disabling the watchdog and preventing resets, but still will not boot the cpu enough to even turn off the start LED. Spot killer is on (blinks briefly when watchdogging on and off).
What we've tried:
5/2/2010 Installing the HS save kit which would eliminate the game rom's as suspects since the HS save uses it's own on-board game rom's. No difference.
5/2/2010 Swapped 6502A from Asteroids to eliminate the CPU as a suspect. No difference.
5/2/2010 Piggybacked the 2114 RAM chips (all 10) with no difference. Essentially eliminating bad RAM as a suspect.
5/2/2010 Checked for continuity between solder side and solder side of both pcb's on the interconnect cable to eliminate bad cable or cold solder problems on cable headers. All pins tested fine at 0.01 ohms eliminating this as a possible cause.
5/2/2010 Tested all fuses on the power supply for continuity. All passed.
5/3/2010 Tested pin 40 (reset pin) of the 6502 with logic probe. It's constantly resetting in game mode and test mode 3-4 times per second. Grounding the WD disable prevented the reset 40 from pulsing. Just confirms watchdog is barking and WD circuit is working.
5/3/2010 Tested continuity on all socketed chip legs through the socket to the solder side of board. A3, B/C3, E1, F/H1, J1, K1, L/M1, N1.
5/3/2010 Removed, cleaned, reseated all socketed chips A3, B/C3, E1, F/H1, J1, K1, L/M1, N1, 6502A.
5/3/2010 Reflowed solder on 40 pin 6502 socket. No change.
What we need to try based on KLOV articles and Vectorlist.org articles:
ROM/PROM B/C3 (036422-01 24pin MIF socket) possibly bad - indicated by continous low tone and possilbly no display. At one point I did hear low tone rumbling noise pattern 16 'rumbles' followed by approx. 10 seconds of silenced, then repeated. This is not likely the problem chip(s), but something to at least test the socket continuity from the chip legs to the solder side contacts to eliminate bad socket(s).
ROM N1 (036409-01 24 pin MIF socket) possibly bad - indicated by no ram tones. This one seems more plausible as this would also prevent CPU boot.
BAD ROMS? 2 of them? - not sure what this means, possibly same as above 2. More homework needed.
EAROM? (ER2055???) possibly bad. Not sure if this board even has an EAROM so I'll check it out.
LS245's bad. This would cause a constant watchdog possibly due to controlling the watchdog timer. This is very unlikely since disabling the watchdog does not solve problem.
Check continuity on all socketed chips on the AVG board. Aux board issues would not prevent test mode from working, so focus on AVG (main) PCB board.
Fixed on 5/4/2010.
Problem was broken/shorted traces under the 6502A chip.