Ok I had a major progress (thought not end yet ,due to my fault), I'll try to show my progress with couple photos ,perhaps will
help some fellows to resurrect their mtx's
First of all a big Thank you to Mr. Andy Key he send me one of his memorycards and testcard rom , which was a definitive help.
ok I done was in order :
I removed the "SPAIN" piggyback ROM , think that was indifferent but I just mention it
then the memocard arrived I plugged it and replaced the PAL with the 3_0 GAL now at every startup I had this screen:
not the best but some improvement over the black screen , I plugged the keyboard , and I noticed I had reset , Ctrl G bell , and cursor movement , corrupted characters but characters.Andy guide me to the VRAM chips , and I remembered that hadn't checked continuity in
the tracks of VRAM and yes I had discontinuity in A6 of leg 13 of one chip (was stupid enough to buy low quality sockets)
repaired the track and have this screen
ok so indeed something to do with VRAM , Andy had mention about the dis-coperitive behavior of Video Processor for several
ram chips due to timing the chips I had on are AM9016FPC mentioned somewhere in primroebank.net as checked replacements
all from NOS stock checked as working chips in my socketed ZX spectrum , a totally random move I replace the 2 bottom chips
with 2 ITT 4116 2N and YESSS
that's curious , we usually prefer all the chips to be the same.
something made the difference but what ?
and now the unhappy end I had already the TIP transistor and regulators on a separate heat sink for better heat dissipation
to put it back in the case I had to replace the heatsink with a smaller one , on the transfer I put wrong way the bolt insulator
of the TIP , make a short circuit , blow the fuse , and now has a nice black screen with continuous tone , and go again from start
Standby alert 