8085 Microprocessor system debugging

[wonderz]

Hello everyone

is there anyone with previous experience on 8085 systems?

I am facing a very confusing situation here.

we have made a two layer PCB for our 8085 system with single 8k EPROm and 2k SRAM . only chip select connectios are obtained using single thin soldered wires.

the system was working perfectly and efficiently for over a month untill we completed the whole project. yesterday as we were doing the finishing jobs after fitting it in box it stopped working. we could see a periodic signal on oscillocsope on A15,A14,A13,..,A8 the same signal was observed on all of them suprisingly the same exact signal could be seen on S0 pin 29. ( or S1 pin 33 I am not really sure about it now) It is so confusing how can the same signal appear on all of them? :roll:

could anyone suggest anything ? could it be due to one of the chip select soldered wires becoming loose while putting it in box?

I would appreciate any comment :wink:

 

[McGuinn]

Yes, or maybe capacitance has affected a floating input/output... Are all pull-up resistors installed?

Did you put it in a potting compound? I just am wonder about this as you don't seem to be able to reopen the box to check the wires manually???