Purchased this frogger bootleg pcb recently from a member for a reasonable price as untested. Pcb was in good shape with no missing components.
Gave it a visual check to see if there is broken traces or components, found a eprom hanging out with some broken legs,soldered them with single core wire and placed back in socket.
Ok let's fire it up........right ok what I have is no sound and no picture, completely black.Scoped the clock pin on the main Z80cpu on bottom board and I got zilch.
Looking at the schematics on the clock circuit I scoped ic.73(74ls368) output pin 7 and got zilch again, accidentally touched the crystal 18.432mhz and the game booted
, looking closely one of the legs of the crystal was broken.
Fixed the leg and resoldered back and strapped the crystal body with single core wire so it won't break again. Rebooted the game but intermittently the game would coin up to 99 and start on its own?also tried to coin but it would not work.When the game was on demo the dopy frog was at the top of the screen?also no sound at all but touching pin 1 (input) to the M51516l amp I got a hiss so good news is the amp is good.
Started investigating the player inputs which is controlled by a 8255 on the sound board(top),all inputs for controls were high on the pins except pin 4 which was low,looking in the schematics pin 4 goes to a 1k resistor array and looking closely there was a hairline crack.
Replaced with new array and fired it up,cool it booted correctly and I can coin and start game but can't play as the dopy frog is hanging at the top of the screen. My suspect of this fault is more likely in the sprite counters so there's 2 counters(74ls161).scoped outputs which were good also clock input at pin 2 was good but pin 9(load) was stuck high,this pin should be toggling. Looking in the schematics this goes to pin 6 of a 74ls139 at location ic41.
Replaced with a new 74ls139 and this got the frog in the correct location, coined up and played ok 👍.
Now for the sound I went straight to the Ay8910 melody chip (top board)and checked all pins signals which were ok and active except the analogue outputs pins 3,4,38 which were dead,these are common on failing so I put in a new one and the sound was back.
Another fixed.
Gave it a visual check to see if there is broken traces or components, found a eprom hanging out with some broken legs,soldered them with single core wire and placed back in socket.
Ok let's fire it up........right ok what I have is no sound and no picture, completely black.Scoped the clock pin on the main Z80cpu on bottom board and I got zilch.
Looking at the schematics on the clock circuit I scoped ic.73(74ls368) output pin 7 and got zilch again, accidentally touched the crystal 18.432mhz and the game booted
, looking closely one of the legs of the crystal was broken. Fixed the leg and resoldered back and strapped the crystal body with single core wire so it won't break again. Rebooted the game but intermittently the game would coin up to 99 and start on its own?also tried to coin but it would not work.When the game was on demo the dopy frog was at the top of the screen?also no sound at all but touching pin 1 (input) to the M51516l amp I got a hiss so good news is the amp is good.Started investigating the player inputs which is controlled by a 8255 on the sound board(top),all inputs for controls were high on the pins except pin 4 which was low,looking in the schematics pin 4 goes to a 1k resistor array and looking closely there was a hairline crack.
Replaced with new array and fired it up,cool it booted correctly and I can coin and start game but can't play as the dopy frog is hanging at the top of the screen. My suspect of this fault is more likely in the sprite counters so there's 2 counters(74ls161).scoped outputs which were good also clock input at pin 2 was good but pin 9(load) was stuck high,this pin should be toggling. Looking in the schematics this goes to pin 6 of a 74ls139 at location ic41.
Replaced with a new 74ls139 and this got the frog in the correct location, coined up and played ok 👍.
Now for the sound I went straight to the Ay8910 melody chip (top board)and checked all pins signals which were ok and active except the analogue outputs pins 3,4,38 which were dead,these are common on failing so I put in a new one and the sound was back
.Another fixed.
