Iam waiting on my replacement parts for my laser XT/3 8086 10Mhz machine.
Ordered two new SN74LS245N chips (i had the previous chips removed for diagnostic the machine) but i have a lot parts laying around.. And also move parts from heap to table, i have lost my eyes on finding the chips again.
Ordered 18 new Dram chips, to replace my old factory 512KB ones. Tried to install the full EMS option and the Parity chips.. Ending in a parity error some where. Iam currently testing the chips to find any culprit.. But still iam looking.
Maybe the base 512KB memory isnt that stable anymore and could end in a sort bitflip and causes the parity error. So iam going back to the basics.. Setting the board back to 512KB memory.. And upgrade it with newer chips. And hoping the parity error goes away.
And iam in a wait for the new DMA controller i ordered recently. (the old one got welded in the socket.) was hard to remove the IC (maybe it was already bad) *thought that DMA controller have a sort of memory inside*
When lifting it out.. Some pins where stuck, and wont wanted to got out. So 1 pin broke off. Now replace it with a new siemens part.
As far iam now.. 1 week ago cleaned the motherboard. Sprayed every where deoxit D5 to insure every contact made well.
Replaced the 40 PIN DMA ic socket
*consider to replace some electrolyc capacitors.
* Consider to desolder the other 74LS chips around the chips which are in contact with the DMA controller and solder in IC sockets. (then could swap out the 74LS logic)
~ At least it can do black and white~