trag wrote:With a spray can and the little tube it comes with, you should be able to squirt solvent in the hard to reach spots... You could also try the dishwasher method. A soak in hot water will probably get the hidden spots. But....it's also possible that the goo ate a via.
tt wrote:JDW, it might be easier to explain if you say draw a black or plain white background in hypercard and make lines in the exact locations and mark them. Then you could count pixels. Although it might be tricky to do fullscreen (maybe a really old HC version) since the micron xceed adds an extra pixel in one of the directions.
bigmessowires wrote:...you might want to monitor the 5v output with a scope, and set it to trigger on anything below 4.8v or so. By measuring with a multi-meter, you won't catch brief power supply glitches.
bigmessowires wrote:If you suspect a DRAM or SRAM chip has gone bad...
tt wrote:...draw a black or plain white background in hypercard and make lines in the exact locations and mark them. Then you could count pixels.
bigmessowires wrote:Does that sound right?
bigmessowires wrote:For 1, there are a couple of other suggested remedies for SimasiMac (other than re-capping) mentioned here: http://www.biwa.ne.jp/~shamada/fullmac/ ... #SimasiMac
bigmessowires wrote:For 2, it could be anything really. Power supply problems is one possibility, but I'd guess it's more likely a borderline component on the Daystar card, maybe triggered by temperature.
bigmessowires wrote:For 3 I agree with trag's earlier statement that it's very likely a VRAM problem. The way the line moves about with color depth makes that pretty clear. His suggestion of blowing cold air on the chips sounds much better than my idea of probing with a resistor, although the end goal of identifying the faulty VRAM chip is the same. Assuming you could find the faulty chip, do you have any source for replacements?
JDW wrote:And yet, when I booted I again got the sad Mac "chimes" and the horizontal lines, as shown in my new 720p video here (please take time to watch it):
JDW wrote:Could it really be that gunk is still causing this?
JDW wrote:I could just run a wire to attach those two points, but I am not sure if that is best. This is a multi-layered board. And unfortunately, I do not know if there are more than 3 layers. Further, I have schematics but I don't have PBC layout files which would show how many wires splice off the same via. Hence, if I've got a bad via, it's easy to fix that via by running a wire on the top and bottom of the board, but that won't help me if there are breaks to that point in different layers WITHIN the board.
trag wrote:I'm pretty sure these are four layer boards, with internal ground and power planes and signal layers on the top and bottom. More importantly, I can't imagine how running a bypass wire would do any harm, even if the board has more than four layers. At worst (I think) it just won't work.
bigmessowires wrote:can't you proceed as you have been, checking out the board with a continuity meter and comparing to the schematics?
JDW wrote:In my examination of several thru-hole vias last night, I noticed that some wires from connectors will route from a connector pin to a via, but then you cannot physically see any wires on the top or bottom of the board leading from that via to another place on the board. Yet, if you hold the board up to the light so you can see light shining through the back of the board, you can then see a tiny little wire inside the board leading away from that via somewhere else.
JDW wrote:Interestingly, despite the +5v line being shorted to Ground, I get the horizontal lines and chimes of death at startup. I would think that with a short on the logic board, I certainly should not get any sound. Yet, the sound works fine, and is quite loud too.
bigmessowires wrote:it actually makes the startup sound "bong" when powered on.
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