UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Sharp MZ-80K help needed on repair

Mark1960 · 9th Oct 2021, 6:41 pm

The clock looks ok to me.

Most likely cause of an intermittent fault would be an IC socket connection, could be IC pins corroded, socket connection corroded, maybe IC pin bent under with a turned pin socket, or a missing gold insert on a turned pin socket.

As it seems to be in a permanent fail it might be possible to find the fault by measuring resistance between IC pins and the pad on the pcb, but take care not to apply pressure that might temporarily improve the connection.

Another possibility is failed through hole plating, I have seen this with boards from the 80s when the pcb manufacturing process was not so well developed. I have a reject z80 pcb from that time that I fitted links through each through hole to get it working. I would have expected this type of fault to have caused a much earlier failure in the life of the mz80 though.

Is there any signs of corrosion in any area of the board? Perhaps close inspection and checking continuity of through hole vias in any areas of corrosion might show a fault.

9th Oct 2021, 6:41 pm	#253
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,298	Re: Sharp MZ-80K help needed on repair The clock looks ok to me. Most likely cause of an intermittent fault would be an IC socket connection, could be IC pins corroded, socket connection corroded, maybe IC pin bent under with a turned pin socket, or a missing gold insert on a turned pin socket. As it seems to be in a permanent fail it might be possible to find the fault by measuring resistance between IC pins and the pad on the pcb, but take care not to apply pressure that might temporarily improve the connection. Another possibility is failed through hole plating, I have seen this with boards from the 80s when the pcb manufacturing process was not so well developed. I have a reject z80 pcb from that time that I fitted links through each through hole to get it working. I would have expected this type of fault to have caused a much earlier failure in the life of the mz80 though. Is there any signs of corrosion in any area of the board? Perhaps close inspection and checking continuity of through hole vias in any areas of corrosion might show a fault.