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Random capacitor on my M72 board

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bodgit

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I've just recapped my M72 and as I was reassembling everything, I spotted this half-attached ceramic capacitor straddling pins 10 & 11 on IC13 on the middle B board:

IMG_2972.jpg


I initially thought it was from me flipping the board over when I was swapping over the electrolytic capacitors so I scolded myself for being clumsy and soldered the leg back on, but when I powered up I get a RAM error. Sure enough if I disconnect the capacitor leg again, everything works properly again, so I don't think I broke it, the previous owner must have intentionally disconnected it.

Is this factory? Should it be there at all? I don't have another M72 to compare with. I thought my board set was an Air Duel, but judging by the foil license stickers, my B board is actually from an R-Type with an Air Duel C board.
 
Not present on my Image Fight.
 

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kikaso said:
Not present on my Image Fight.
Click to expand...
Thanks.

The only other capacitor I have piggybacking an IC is IC47 just like your Image Fight so that one is factory. Guess I'll leave this other one disconnected, my M72 seems to be working just fine without it.
 
connect it.
caps like that are common because some chips are not as good as they could be and the factory has to do bodges to fix glitches.
 
stj said:
connect it.
caps like that are common because some chips are not as good as they could be and the factory has to do bodges to fix glitches.
Click to expand...
Did you read my post? If I connect it, my board stops working. It goes through the scrambled screen memory test and gives me a RAM error. If I disconnect the leg, my board boots up fine so I'm inclined to leave it disconnected.

Looking at the datasheet for that chip (74x373), it looks like the cap was bridging the C/CLK pin to GND. Not entirely sure what putting a cap there would be doing.

It would be curious if someone with an R-Type board set has that cap installed given my middle B board was originally for that. Maybe it was needed due to the differences between R-Type and the other M72 games (from the PoV of multi suitability at least)?
 
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