Such a cool place and so incredibly heart warming to see that the Mega PC lives on. I hope i'm not late to the club. I also hope the thread is just taking a rest.
I recently found my old Mega PC (with the 486SLC 25MAB chip) in my storage facility and with it all my original games and disks. I still think i have the keyboard, joystick and game pad somewhere but i was lucky to have found both the system and monitor in very original condition. You can imagine my delight when i discovered it all working again when powered up. The (noisy!) sound of that 40MB drive almost had me tearing up, honestly. The Mega PC, which i had from new, was my last in a whole string of Amstrad systems i bought into before moving on to Dells starting with their first Pentium 60. Goodness, we even had each one of Amstrad's first and send generation Emailers!
However (and yes, the tone drops a little), the dead battery was so kind to do its thing and cause some greenish blue fuzziness around the board which did eat up some of the traces. I have attempted to repair some and it's been largely successful but i may return to this in the future. The main problem at the moment is that whilst it POSTS fine, there is clearly something wrong with the disk controller: errors on bootup are the two Diskette Drive A error and Fixed Disk Controller Failure messages.
Curiously, i do vaguely remember having this problem over 20 years ago and i think my simple workaround was use of the IDE header on an ISA sound card but my memory fails me. I really want to try and fix this.
I obtained the service manuals (my thanks too to @dioxaz) and am probing the WDC76C20 for faults. It appears to be powering up fine and traces to/from it are also fine. Those traces around the battery affected some of the power conditioning but with some repaired, it is not seemingly affecting the controller. I don't have an oscilloscope but i suspect i am going in that direction. That both the chip is controller for both floppy and hard disk suggests it is either a problem upstream or that the actual chip is faulty. However, this chip was hugely popular for PC clones at the time and i have not come across other stories of it failing.
I hope to post up pictures of another saved Mega PC but in the meantime, is anyone able to shine a light as to what i could do to troubleshoot the onboard controller?
Cheers!
Pops
