Fixed Mac128K board (was Re: Repairing Mac128K board - memory problems)

On Fri, Sep 20, 2013 at 10:16 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote: In anticipation of pulling and replacing 1/3 the DRAMs on this board, I tried the trick of a dry-fit piggyback with known good chips on the locations marked as bad. I can report 100% success. I stuck 6 new chips on the 6 bad chips and got past the Sad Mac. In the light of the several reports I found on support forums, all I can imagine is that if these people replaced their bad RAM chips, either they misread the conversion table and replaced the wrong chips, they damaged the chips or the mainboard traces during the repair process, or they just have a bunch of cold, dry solder joints. Present state: machine gives "bong" when turning on (it always did), usual screep wipe happens, then the "[?]" disk icon flashes. I have one 400K drive, an OA-D34V-22, and (for now), Rev A ROMs. This combination does not work. It tries to read disk, ejects it, then asks for another one. I already have the -B ROM images and just need to burn a pair of 27256s since that's an easier path than locating a working, original revision OA-D34V drive mech. On the OA-D34V-22 I do have, it did require removing petrified grease from the old eject mechanism. I have some white lithium grease I'm contemplating using unless there is some magic grease the job requires. So the repair is nearly complete. Bad trace/repair damage found/fixed, bad RAMs identified and tested, and a couple items to complete to finish the job. -ethan