System 16B black screen: If it ain't broke, do a bad recap to break it

[9999 Damage]

Short version
My System 16B is showing a black screen after a motherboard recap. The power LEDs come on.

Background
Emboldened by successfully recapping a few arcade PCBs and consoles, I thought I should do a preventative recap on my System 16B before installing it in a Semload case. A few of the through-holes had stubborn solder trapped inside, and I lightly burned the PCB around a couple holes. I didn't notice any lifted pads, but it's very possible I lifted some pads after applying too much heat.

When I powered it on with an installed 16B Multi, I was able to play fine initially, but Shinobi froze after about 20 seconds. After that, I could switch games, but it would freeze until I put light rotary pressure (!) on the Deluxe Selector's dial. Seriously, I could pause the Golden Axe title screen by releasing pressure, then resume by restoring pressure. But after I played with that for a minute to understand what was happening, I got a black screen, and couldn't get it to recover after power cycling. I tried swapping in my old Bay Route ROM board conversion, but I still get a black screen.

Troubleshooting

1. What should I do next? Presumably one or more caps isn't installed correctly, maybe because there's a lifted pad and it's not actually in-circuit. Is there a way to test each cap to confirm it's installed correctly? Or does the black screen confirm the board is already damaged in a way that will require troubleshooting (and repair, if possible) by someone who actually knows what they're doing?
2. I recall replacing either the Z80 or 68000 as part of the multi install. Is there any reason why the non encrypted Z80 or 68000 wouldn't work with a Bay Route ROM board conversion?

 

[advans14]

1. caps should have polarity marked on the board. if they dont, post a pic. if the board was working before, it is obviously the work you did so you need to inspect each spot where a cap was changed, no way around that or guessing on our part can help. a thorough visual inspection needs done.
2. a stock bay route rom board won't work with unencrypted parts assuming the bay route rom board is OG with OG roms.

 

[SCUBA King]

Short version
My System 16B is showing a black screen after a motherboard recap. The power LEDs come on.

Background
Emboldened by successfully recapping a few arcade PCBs and consoles, I thought I should do a preventative recap on my System 16B before installing it in a Semload case. A few of the through-holes had stubborn solder trapped inside, and I lightly burned the PCB around a couple holes. I didn't notice any lifted pads, but it's very possible I lifted some pads after applying too much heat.

When I powered it on with an installed 16B Multi, I was able to play fine initially, but Shinobi froze after about 20 seconds. After that, I could switch games, but it would freeze until I put light rotary pressure (!) on the Deluxe Selector's dial. Seriously, I could pause the Golden Axe title screen by releasing pressure, then resume by restoring pressure. But after I played with that for a minute to understand what was happening, I got a black screen, and couldn't get it to recover after power cycling. I tried swapping in my old Bay Route ROM board conversion, but I still get a black screen.

Troubleshooting

1. What should I do next? Presumably one or more caps isn't installed correctly, maybe because there's a lifted pad and it's not actually in-circuit. Is there a way to test each cap to confirm it's installed correctly? Or does the black screen confirm the board is already damaged in a way that will require troubleshooting (and repair, if possible) by someone who actually knows what they're doing?
2. I recall replacing either the Z80 or 68000 as part of the multi install. Is there any reason why the non encrypted Z80 or 68000 wouldn't work with a Bay Route ROM board conversion?

Post a pic. Sometimes there is an MCU on the 16b, that has to be removed or it does weird stuff.

 

[9999 Damage]

Thank you, both.

I’ll take another look when I get home from travel, and post pics. I was paying attention to cap polarity and double-checked against the symbols on the board and a pic, but it’s always possible I missed something.

@advans14 Good info about the encrypted/unencrypted ROM board vs. chips. The ROM board was a conversion, but AFAIK worked with a stock Z80 and 68000.

 

[advans14]

yeah not sure. i think there were some 16b stuff that doesnt require encrypting, but like scuba said there is the mcu at the top left. also sometimes the z80 is different. pretty sure they never released a non encrypted game on the 16 from factory (but i dont know much the unique variants)