The cart won't run at all. I tried to read some bytes from CPU area ($8000-$FFFF) and PPU ($0000-$1FFF) using MyKazzo. The reads are repeatable (i.e. another read from the same address range returns the same data). However I found out weird issue - first read $80 bytes are zeros, next $80 bytes contains data, another $80 bytes contain zeros, etc. That is both in PRG & CHR.
Then I desoldered all chips. I tested 74XX chips (74174, 74139, 74153) using my homemade chip tester. They seems to be fine. Next, I dumped both PRG & CHR using memory programmer.
I found out that this $80 bytes zeros/data pattern are in whole PRG / CHR rom.
But the remaining bytes of PRG seems to be OK. For example, I found the following sequence:
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ALPHABETAGAMMADELTAEPSILONZETAETATHETAIOTAKAPPALAMBDAMUNUXIOMICRONPIRHOSIGMATAUUPSILONPHICHIPSIOMEGAINFINITYTARGETATTACKGAME
If this rom would be available online, I would just replace the broken mask roms with preprogrammed EPROMS, but I doubt I can find this set. And the 31-in-1 (Pirate Cart) (J), available online doesn't seem to be this same set.
So the reason of not working is probably because of broken PRG & CHR. Are they mask-roms?
How is possible they are broken in such funny way? Did they broke them in factory during writing?