The address/data bus to the MegaII VLSI is dead on, otherwise you wouldnt be able to generate any legible characters.  The chip very well could be bad. But it would be odd, but no…

One of these days... when I get time... HAHAHAHAAHA.... I need to go through and compare the two analog boards and figure out the differences. 

Pitou said: I already checked all pins with an oscilloscope. Continuity is good. Signals seem to be on all pins except for 1,2,4 and 6 if I remember correctly. Again, I'm not…

Fix it please!

I like that G5/Mac Pro case design.

Schmoburger said: I had good luck with a 2.0DP. The owner had the cooling system fixed under warranty but said it wasn't stable after  that and gave it to me. I didn't look a…

Funny http://www.ebay.com/itm/Vintage-APPLE-Macintosh-Classic-Model-MO420-Computer-With-keyboard-mouse-1991-/251961675256

I would date-code the analog board.

OK, good to know.  I just wanted to make sure I wasn't messing up a prototype before I started stealing parts.

Datecodes make it seem unlikely to be a prototype. The 512K was released in '84 but the IC date codes there are all from late 1985, such as 8547, 8543, 8598 and another 8543.

I already checked all pins with an oscilloscope. Continuity is good. Signals seem to be on all pins except for 1,2,4 and 6 if I remember correctly. Again, I'm not sure what to expe…

I had to review again a few times the video as the first few seconds as comes up scrambled on the old OSX 10.4 QuickTime. Now I see the start up screen come up scrambled but not re…

the one thing i do not like about the 640x480 mod, is the 47HZ refresh rate... i mean 60hz is bad enough. seems when i get mystified A/B's in the caps are extra cooked.           …

Well in theory only the mobo could be a proto. The rest would not be, just an unlabeled case.

This is something totally different. ProDOS-IIgs works with the windows and other things and all. So there is nothing wrong with the system at all. This is a software issue, looks…

Pretty sure it's BGA.

Yep it's almost guaranteed that the PSU is cactuar, and this will be the primary issue that prevents it powering on... However it is likely that it has logic board issues or will h…

There are two electrolityc capacitors on the inverter board, one is a 47uf 16V, the other is a 33uf 10V

I'll examine it more closely when I get home.  I couldn't see anything that was different, except for the text on the motherboard.  But I only have 1 other 512k to compare it to. …

I'm not able to get into Applesoft BASIC using ctrl-reset. I also tried running BASIC from a system disk. See this video. test.zip Any idea? Pitou!

Hmmmm I might  drop it down a slot in that case and try again. I was getting a fair bit of wierdness all round after I put it in so that is likely the answer... the more you know!

Sad to hear the demise of such a machine. Q: Cant the U3 memory controller desoldered, the pads cleaned up and fixed and the chip soldered back on?

The Q800's PSU might not be able to handle two PC Cards. I would recap the PSU First. If the PC Cards can do background processing, then maybe it can be done. Like Trash80toHP_Min…

Perfect! I did have M0420 in the list at one point, but could not find a visual example of one for sure. So this helps a bunch!

360alaska said: Actually it has been done before: http://www.fenestrated.net/~macman/CC575/ Click to expand... 360alaska.... Wow!!!  While I do not like taking a dremel to…