MV-4F can't read slot 2

So I'm fixing up a non-working 4 slot board (the tiny version of MV-4F) I got on the cheap about a year ago. After a physical inspection, I found a heavily gouged trace on the underside of the lower board and repaired it. I also put in a UniBios 2.2, and cleaned it extensively. The battery looks reasonable, though I intend to replace it anyway sometime this week as it is old.

I started it up and it only was able to see slots 1 and 3 initially, but after some fiddling with the cart and clearing the backup RAM, it now reads slot 4 as well. No matter what I try though, it does not read slot 2. I've been over this board a dozen times and have cleaned slot 2. I can't see anything physically wrong. Could anyone please give me some pointers as to where the problem might likely be so I can narrow my search.

How do the pins look in the connector for slot 2? Maybe they are not making full contact with your carts which you could fix by pushing those pins inward a little more.

xiao_haozi said:

How do the pins look in the connector for slot 2? Maybe they are not making full contact with your carts which you could fix by pushing those pins inward a little more.

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I haven't tried pushing them inward more so I suppose I can't rule it out completely, but none of them look out of whack. I cleaned the slot with an old SNES cleaning kit strip, which is the width of a pcb. During the cleaning, the strip made apparent good contact with all the pins.

The data from the program ROM can't be read properly. This could be a dirty slot, bad slot connector, or a bad IC/broken trace on the top board.

RJ

I've tested for continuity on any suspect traces on the top board and they all seem fine. I also verified that the pins on slot 2 are all making excellent contact with the cart pcbs.

On the lower board I replaced the original battery. It's worse than I first suspected as the hot glue was covering the bad looking areas but it appears to be only superficial.



This was the only obvious damage I could find to the board that I haven't already repaired, but slot 2 is still unreadable. Aside from that the board works great. I am handy enough to locate and fix physical defects, and I do have a parts board, but determining if there's a bad IC is beyond my experience.

Check continuity on those thin traces running next to the battery. BUT, I don't think a failure of one of those would cause a single slot to drop out.

RJ

They all test ok. Only cosmetic damage to this area.