Here we have a original fighting hawk pcb which was given to me as a free game,i was informed it was working but with corrupt graphics.Here is the pcb on my bench.
Lets fire up the hawk............🦅
ok the good news it boots
,looks as though theres a background grx tiles issue and there is no sound at all.I coined up and tried to play the game but theres another problem where when the game starts the hawk acts crazy and goes to the top of the screen without touching the joystick also keeps bombing on its own😵💫.
I decided to tackle the tile grx problem and worked out where the data is stored,ther are 3 mask roms labeld B70-01,B70-02,B70-03.
i did a romident on all three and one failed (B70-03)
worked out these are 512kb mask roms and i used a jedec type 27c400,got the file and reprogrammed it.
thats more like it,the graphic are back and look awesome.Now graphics are ok i went straight to the audio circuits,all chips in red are used to generate the sounds.
first i checked the z80a cpu's data and address pins all were active except pins D3 and D4 which were at very low level close to ground 😲,all the data pins from the z80a are tied to the sound rom next to it labeled (B70-09) ic31.
so pins 15/16 of the eprom were also close to ground level.I took the eprom out of its socket and tested it using my tester.
what the hell 😳,pin 15 reads nearly 46 ohms and pin 16 read 120 ohms.this tells me the eprom is bad.
to be continued.............................🦅
Lets fire up the hawk............🦅 ok the good news it boots,looks as though theres a background grx tiles issue and there is no sound at all.I coined up and tried to play the game but theres another problem where when the game starts the hawk acts crazy and goes to the top of the screen without touching the joystick also keeps bombing on its own😵💫.I decided to tackle the tile grx problem and worked out where the data is stored,ther are 3 mask roms labeld B70-01,B70-02,B70-03.
i did a romident on all three and one failed (B70-03)
worked out these are 512kb mask roms and i used a jedec type 27c400,got the file and reprogrammed it. thats more like it,the graphic are back and look awesome.Now graphics are ok i went straight to the audio circuits,all chips in red are used to generate the sounds. first i checked the z80a cpu's data and address pins all were active except pins D3 and D4 which were at very low level close to ground 😲,all the data pins from the z80a are tied to the sound rom next to it labeled (B70-09) ic31.so pins 15/16 of the eprom were also close to ground level.I took the eprom out of its socket and tested it using my tester.
what the hell 😳,pin 15 reads nearly 46 ohms and pin 16 read 120 ohms.this tells me the eprom is bad. to be continued.............................🦅