After successfully completing the 640x480 mod, I thought the next step would be to try oevrclocking the LC575 board (http://gabezing.sytes.net/lc575-40mhz-e.html).
I used a 21.7 Mhz oscillator, and that did not work. One problem is my RAM is 80ns. I got chimes, but no video (black). Since I don't have any 70ns VRAM, I tried to undo that change. I snipped the oscillator away and put my LC575 board back in the CC.
That's where my latest problem begins: I have no chime, no video, and only initial hard drive spinup (no OS load).
So I checked to make sure there wasn't any cold solder on the board. I removed the battery for about an hour (to zap the PRAM), and re-seated the RAM and VRAM.
Still no go. Can anyone think of anything I haven't done?
Sounds like you fried a chip, henses no noises. It should at least make the chimes of death...
Try replacing the original oscillithing.
How good are your soldering skills? Could you have burnt a track up?
I doubt it. But I am wondering if my soldering loosened up a connection between one of the two chips that needed wiring and the logic board. No time to check it right now, though.
Anyone else have any other input - I'll be back at work on it tonight?
One thing's for sure - you're going to need that 70ns VRAM to do the overclock. So why no try putting the oscillator back on the motherboard - if you get chimes you know you haven't fried anything. Then go hunt for fast VRAM. On the other hand, if you don't get chimes, you're fried, so go hunt for a new mobo.
I fixed the problem. The 8th pin on the clock (to be exact - the "MC88916DW70" chip) hadn't been pressed back down enough on the board, so I soldered it and I'm back up again.
Now I'll wait to see if I find some 70ns VRAM before I try that upgrade again.
Word to the wise: If you add an oscillator and then decide to remove it, make sure that 8th pin is making contact with its track on the board. Even if it looks like it is, it may not be, and soldering may be required.