My friend Silvio kindly donated me a couple of faulty boards, this ‘Captain America and the Avengers’ was one of them:

I was expecting some boot troubles but when I fired up it I got this:

All was OK except for sprites that were all missing.Since I already worked in the past on similar Data East hardware I knew that sprites are generated by some ASIC, in particular the one marked  ‘DATA EAST 52’:

Infact, when I firmly pressed this ASIC, sprites were restored.Proving the tightness of the individual pins with a needle as I usually do confirmed that some pins were lifted.So time was to do a reflow of this chip and this was enough to fix the board completely.

Thanks again, Silvio!

I got this board always from Ebay sold as faulty:

When I first powered up it I got a solid black screen.Probing the CPU I noticed some strange activity on 68000 address/data lines and watchdog was indeed active.So I piggybacked the two 62256 work RAMs @U1 and U4 and  I got this:

Despite the message error,this was a good sign of life so I desoldered the two RAMs and I found them really bad:

Replaced them but still black screen and watchdog active.So, I noticed there were other two RAMs connected to 68000 CPU but not directly but through two 74LS245 and enable pin of these were stuck high.I traced back it to an output of a 74HC4075 so I started to test it with logic probe and while I was probing it suddendly the PCB succesfully booted to title screen:

I can’t really explain this but now the PCB is now working perfectly every time I power it on and this is the most important thing.See you next repair!