New Life Games Tech Forums

this is a 2 board bootleg,
the pcb came dead, looked at the clock circuit and found bad repairs with giga wires to clock and ics and big solder blobs, replaced wiring with 30AWG kynar wire but still no go.
looked further and the 'ls74 near the xtal was replaced and board started alive but with no sound.
i socketed the sound Z80 and ran a bus test with fluke 9010a, and it gave me data bit 7 stuck, so i cut every data bit 7 legs on the data path and reran the test -> ok.
started resolddering legs to find the culprit was yamaha ym2203 !
socketed and replaced still no sound.
i found that the TL074 that biases the DACs (YM3014) was giving out -2V instead of +2.5V, obviously killing the DACs.
so i replaced TL074 and 2x YM3014 and the sound came back !!!

jamma adapter completed the job.

after a while the board developed another nasty problem: it resets or freezes after some minutes of warming up, then resets after just 1 minute.....
armed with coolant spray i traced it down to prom  labelled "4" near Z80 #2 (it was an Intel P27256 plastic prom); replacing it with a 27C256 from a scrap board fixed the reset/lockup problem.
i never thought a prom could develop warm dependant defects, i thought RAMS where  much more prone to this !

Zab

I've seen warm defects that would come and go if you tapped on the chips. I think it was a bond wire issue where it connected to either the die or the pin for the IC leg.

I picked up a 2 board Super Bobble Bobble bootleg off eBay very recently.

The video would black out completely or the picture would be abnormal, tapping the board fixed the display or broke it.

I initially thought that I was dealing with a bad connector to the video board. I found that one of the pins on the sn74L377n ( ic98 ) on the video board had barely any solder on it & it was making intermittent contact causing the issue.

These boards tend to have some irregularities, some of the chips are not completely pressed into their holes although the pins are still making contact.

Yeah, you have to check factory soldering. First thing a board gets when it's put on the bench is a visual check for scratched/gouged traces, spills/foreign substances, bent pins, etc.

I had an old ISA video card that had a surface mount tantalum cap that wasn't soldered on one end and an SVGA monitor that had no solder on the + lead of the bridge rectifier. It's amazing how many factory screwups there are, like a switching power supply that they didn't remove the insulation from one pin of the switching transformer... Crazy!

RJ

Its quite surprising that this board would have left the factory in that state and was probably used for many years and perhaps exhibiting that same problem from time to time, a small flex of the board or tap enough to get it working until it happens again. These boards were very clean when I received them much to my surprise for a very popular game,  I assume they gave up on it and stored it somewhere for many years.

I just recently received a King Of Boxer through eBay ( one of my fav games ) with a very similar problem, there was a bypass to repair a broken track but it was not a good repair & moving the board/wire was enough to break the display so I removed the AWG wire.  I could not find a hint of corrosion or break in the track, I used a magnifying glass and could see that the track had a very small gap, it appeared to be a manufacturing issue to me rather than a gouge, it still had the original lacquer intact where the fault was. I don't understand why anyone would use a patch like that with such a tiny break. I just rubbed back the the trace on both sides to the bare copper and bridged it with a smidge amount of solder & sealed the repair with PCB lacquer. Good as new.

Not too surprising.

I've seen several Capcom boards from the Buster Bros/1943 era of gaming that have a single PLCC chip with multiple pins barely soldered. You flex the board and the solder on those pins crack and you have odd display problems. Reflow the chip and the problem goes away.

It's very easy to see the weak solder on a few pins on that chip.