hi to everyone,dug out my original burgertime with a sound fault.video is all good and plays well but all i get with sound is a pulsing single tone.first thing to check was the sound rom at location 12h which romident ok.
after this i went straight to the 2k(sram) at location 10h,using my scope the address and databus was busy except the chip select(pin 18) which was stuck high
followed pin 18 of the sram to pin 1 of ls42 at location 19c,looking at the datasheet this is a o/p so i removed the chip and verified it using my programmer which it passed.resoldered it back in,decided it may be the sram at fault so i removed and did a test
fitted a new socket
then installed a new 6116 sram
powered up the pcb and music to my ears!gave it a soak test in my cab and all is good.
after this i went straight to the 2k(sram) at location 10h,using my scope the address and databus was busy except the chip select(pin 18) which was stuck high
followed pin 18 of the sram to pin 1 of ls42 at location 19c,looking at the datasheet this is a o/p so i removed the chip and verified it using my programmer which it passed.resoldered it back in,decided it may be the sram at fault so i removed and did a test
fitted a new socket
then installed a new 6116 sram
powered up the pcb and music to my ears!gave it a soak test in my cab and all is good.
