Its a 30 years old PCB board and the company stopped making it, so no datasheet and no schematic. It's a hard troubleshooting, the main issues is beeping continuously, after the hard time watching all ICs and stuffs, still couldn't figure out where the problem is.This is a machine controller which is used to dig underground for sewage repair system.
I have lots of those boards with 99% having the error of beep. The beep is continuous beep and no break on between.
I checked all capacitor, no sign of sort, the IC looking good, no burn marks as well as any damages. The SRAM, Flash seems ok as i used that from the working board, MSDOS is good as i used that also from working board. Where am i wrong?
What more to do?