Super Bobble Bobble (Bubble Bobble bootleg) repair log

[Zabanitu]

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.

[Zabanitu]

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

[channelmaniac]

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.

[palindrome]

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.

[channelmaniac]

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