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Some updates: 1. To see what I mean about the screen being nicely bright even with the slider quite low, look at the final picture of my original posting. That's probably around 50 mA. 2. I took a thermal image of the circuitry at full brightness. The hottest part is SS34 diode on the step-up...

I just tested the current usage. I disconnected one of the wires going to the LED strip itself and inserted my multimeter in amp mode. Here are the measurements at various levels of the control panel slider: 100%: 440-390mA dropping slowly. Far too bright. 85%: 220mA stable. Too bright. 50%...

Correct. For the first item, I've ordered a couple of other small step-up converters to test. There is one other possible negative, which is I need to see if I can get it to damage the LEDs at the maximum brightness. Because the circuit is advertised for screens as small as 7" tall, perhaps it...

I bought a backlit Macintosh Portable (M5126) that needed a recap and minor cleanup. Upon powering up, everything initially worked. However, within 30 seconds I could smell burning and quickly switched it off. I removed as many accessories (cards, hard drive, floppy etc) and tried again...

If you post a copy of your drive image (whatever is the smallest that exhibits the symptoms), I'll try it on my Toby card and Mac II.

I'm not giving up on this. I swear I've seen it before. Based on Apple's ROM code, highlighting was really tricky and there were a lot of patches for it. Patches were stored in the System based on the ROM 'family" (128/512, Plus, II/IIx, IIfx/IIci/IIsi). To save space, when the System was...

Did you use the same disk image on the II as the IIci? Just to rule out a software / OS issue. Can you describe this further? Is this a ROMinator on the IIx? The fact that the glitch doesn't show on the IIci is very interesting. It rules out the card, adapter, and LCD -- which is progress.

That's crazy. Definitely related to highlight. What system version?

Try changing the highlight color in the Color control panel (?) to something like yellow.

And, it is only scrambling inverted text. That's a clue. Have you tried booting with extensions disabled?

Very interesting. It isn't the LCD. 1. Does it happen every single time in 256 mode? 2. Is the scrambled text always scrambled the exact same way or does it look randomly scrambled differently each time?

As everyone has mentioned so far, adding VRAM generally increases the maximum number of colors and resolution only. However, on accelerated NuBus/PCI/AGP cards, adding VRAM can speed up graphics. For example, the Apple 8*24 GC card can vastly speed up offscreen graphics with additional VRAM...

Tip for English listeners: When I played this video embedded in the TinkerDifferent page, it did not translate the audio. If you open it directly into YouTube, then it will.

Good catch! Not nickpicking at all. I put my notes up online to save trouble for other people. If someone plugs something into that internal connector then they will be on the same "slow" bus as the external connector and can have ID conflicts.

Hmm. I saw a couple of posts from people claiming they made a 4MB PCB layout, but I don't actually see the layouts themselves posted online. If I run across anything I'll let you know.

I recently picked up an 8600/300. I ran across a couple of interesting tidbits while playing with the computer. This is the enhanced model of the 8600 (Kansas motherboard) and stock 604ev @ 300 MHz CPU. For my tests, I'm using System 8.1 with the default extensions. RAM The computer came with...

If this is a 5120, it is a common issue that powering up sound (for the chime) introduces electrical noise into the 5V line and scrambles the CPU, resulting in sad mac. Connect a bodge wire to the sound power signal as shown below. If your Mac boots reliably, you can just leave this workaround...

Is this a 5120? If so, try adding a temporary bodge wire as shown in purple. There seems to be an electrical noise issue in many 5120 Portables when the sound circuit turns on. It causes the CPU to scramble. The above bodge just keeps the sound circuit on all the time. It is a workaround...

Let me know if you run into anything I can help with. Definitely double check for incompatible memory and make sure the board isn't shorted somewhere.

REPLACEMENT PARTS If priced reasonably, I will pick up battery bombed boards to repair other machines. In this case, the missing CPU and FPU were replaced with ones from a battery bombed board. The tops are ugly but the chips are solid. Replacement/repair summary: 1. New speaker 2. New ROM...