Having had some recent success repairing the ZX Spectrum, I decided to spend my day off work today doing some other “repairs” to retro computers. The one of you who reads this blog will hopefully remember the Atari XEGS which had new ram fitted to no avail, yep that was first onto the desk of doom. I recently ordered the 74LS138 Demuxer IC which was next on the list of possible failures concerning memory faults.
As the new silicone chip is on its way I cut the legs off the old one and de-soldered the reaining legs. Then having solder sucked the holes clear, fitted a socket in place ready for the new 74LS138 IC.
Now it sits and waits for the Royal Mail delivery to arrive, and I move it aside for my next victim.
I have my original ZX Spectrum from 1983, but it has a very yellow display, today I was going to replace the caps to see if that helped. On opening it up and looking around I noticed that a couple of the links which are on the others have been removed on this board which also has socketed ram so looks like some factory mods. I am going to speak to the gurus on Spectrum Forever first
I also recently bought a Spectrum to donate it’s case for a new 128k Just Speccy plus board when they are ready. Just thought that while waiting i would see what needed fixing on it. On test it showed IC15 and IC16 were possible faults. I opened it ready to solder and found this happy sight..
All the upper ram and associated ics are socketed, this may have been a 16k upgraded to 48k. Anyway, to the job in hand, new ram to be fitted now very easy to pop one out and fit a new IC, so a few seconds and that is done. It also had non working keys, so I cut back a suspicious looking keyboard membrane tail before reconnecting it. Back together and time to test. All memory tests passed ok, but when dropping back to the Spectrum ROM the screen is garbled (Brendan Alfords test rom did report unknown or corrupt rom in the tests so no fault in that).
I will keep the board no matter what, as ULA and ram is all good, so can have a rom transplant if needed. And that is all for now, until the 74LS138 arrives for the Atari.
