Now this board is a relatively new investment (from the same batch as M.I.A.). A bootleg of SNK's Fighting Soccer. Before even connecting it, I could see that it have seen better days.
Here a broken cappy...
Wired the -5V on the extender and hooked the board up again.
A lot of the sprites had horizontal stripes through them.
Now, it way getting late and I felt a bit tired. I did however decide to do a little piggy-backing of TTLs before going to bed. The board have a cluster of 3 245's in the middle and I just happen to have a tube of them on the table, so I thougth: Let's give it a try:
I quickly desoldered the IC and put it in my Top2005+ for testing...hmm, the test came out successful??? The one I've used for piggy-back (the one from tube) also passed the test.
- Fitted a socket and inserted the new one: Stripes through sprites!
- Inserted the old one back into the socket: Stripes through sprites!!
- Piggy-backed the new one on top of the old one: Still stripes through sprites!!!
Now I was really puzzled...Then tried piggy-backing the new on top of the 2nd 245 in the batch of 3: No stripes??? WTF!
I wanted to get to the bottom of this, so desoldered the 2 others as well and fitted sockets.
Put the old ones back: Stripes! (MOAN!)
I discovered that one of the 245's wasn't inserted fully into the socket. With the board still running I gave it a push, and the stripes went away?! Released the pressure and stripes came back. Began pressing on IC's in the surrounding area: Same thing happend!!!
Now we are getting somewhere; this smelled an awful lot like a short-circuit of some sort.
When looking closely at the joints on the solderside, there was alot of them looking very nasty:
So started a shotgun-scheme, where I did a reflow on the nasty joints I could see checking the board every time. After about 10 of them with no luck, I decided to change strategy into a more systematic brute-force approach.
Started by cleaning the lower half of the board using rubbing alcohol and a toothbrush.