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48MB RAM in a 520c

Done it. 48MB in a Blackbird. RAS[1] is indeed an unused pin on the 500 Series, someone kindly helped me to locate it by beeping out their 190 board. It's right inbetween RAS[0] (onboard RAM) and RAS[2:5] (RAM expansion) which is pretty logical. I'm going to tidy up my work and try to...

Cool, this is coming together. The other '040 PowerBook that uses the Pratt IC is the 190 Series (I don't think the Duo 280 does). The 190 officially maxes out at either 36MB or 40MB RAM, depending on whether it has 4MB or 8MB built-in. Now, I studied some photos of its logicboard: the onboard...

@joevt Some relevant data from the 520/540 Dev Note: I believe this is the 48MB array you referenced in the ROM code, right? The following refers to the RAM card connector: This confirms the existence of 6* RAS signals, of which 2* are on the CPU card. Only 1* of these is used for the...

Correct.

“It” is the PowerBook 520/540. I threw the modded CPU card into my 520c chassis for the experiment, but there’s no difference between a 540c. They have same ROMs and machine ID. The CPU card is the same electronically, it’s just a different speed grade. Nice sleuthing, I’ll look for another...

This has been on my mind for ages, so tonight I finally modded one of my homemade 32MB RAM cards (the one I showed in post #37) as in the following photo. I followed Toyoki's method, and piggybacked 4*2MB chips on top of one of the banks, except for pin 7 (/RAS). I then used enamel wire to...

One can’t reball it?

But I do plan to revisit it. I also need to get a new eject gear.

No, the drive is sitting on a shelf being sad.

Yes, but OP had highlighted one of the vertical ribbons, so I was just responding to that hypothesis. I didn't know the horizontal ribbons could take out half the screen - interesting.

What I meant was that it seems like it’s something other than the ribbon cable you highlighted, because a localised failure there wouldn’t cause half the screen to cut out. This is what I would expect to see: I feel your pain because I’ve had to go through exactly 4 of these panels in order...

Ah, Ok. Do you have a link for legit chips?

I need to get the same chip for my LC475. Just to confirm, it’s safe to buy from this link?

Also I don’t think it’s an issue with the display connector highlighted, as this would cause a more localised issue whereas you’ve lost half the screen. More likely to be a bad trace or via caused by cap leakage.

FREE KEVIN

Found a couple of hours after work to start cleaning up the battery damaged LC 475 board. Egret and DFAC-II will have to come off during the next repair session. Does anyone have a Mouser part number for the common mode choke and microphone input port (the longer one) pictured?

Which machine was that on?

Nice. I want the PowerBook grey one.

:) Nice when things work out, and you’re both in Italy!