I see some radial through-hole 'lytics on the logic board as well, did you test and replace these?
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Building a Dual Floppy Macintosh Portable
- Thread starter Patater
- Start date
I replaced all capacitors on the Portable, including the through-hole ones. The Macintosh Portable through-holes are plated through-holes. This means that solder is supposed to go down through the hole along the sides of the lead. It is easy for me to see that I had proper fill (at least 75%) when working on the axial capacitors, but it is harder for me to verify this with the radial capacitors.
ok. if it isnt capacitors, i would get a scope, or DMM on some of the voltage points of the machine. this way you can see what the power supply regulation is doing. you could have an open tantalum cap that came new, and a scope would find it. but its extremely RARE.
if everything is keen there, i believe one of your VLSIs may have failed. or possibly RAM, but i doubt RAM as your not getting a RAM code. your getting a code that represents an error in the glue logic, or power to the glue logic/CPU. possibly if the voltage supply is low, noisy, you can have it "glitch" the CPU causing a core fault in one of the pipelines by it interpreting instructions one way when it was actually read another way this would cause extremely random exceptions. from illegal instructions to bus errors.
Easy way to eliminate the CPU voltage is probe it. if it looks ok, then it all points to that VLSI.
But at the same time, watch all your bus lines. those resistor pack filters are notorious for going bad as well, so when some logic is requested to "tri-state" it can still cause noise on the lines, however this would cause uncontrollable buss error codes. but a scope is the best thing to have here. itll nitpick at stuff that isnt supposed to be there, or is....
if everything is keen there, i believe one of your VLSIs may have failed. or possibly RAM, but i doubt RAM as your not getting a RAM code. your getting a code that represents an error in the glue logic, or power to the glue logic/CPU. possibly if the voltage supply is low, noisy, you can have it "glitch" the CPU causing a core fault in one of the pipelines by it interpreting instructions one way when it was actually read another way this would cause extremely random exceptions. from illegal instructions to bus errors.
Easy way to eliminate the CPU voltage is probe it. if it looks ok, then it all points to that VLSI.
But at the same time, watch all your bus lines. those resistor pack filters are notorious for going bad as well, so when some logic is requested to "tri-state" it can still cause noise on the lines, however this would cause uncontrollable buss error codes. but a scope is the best thing to have here. itll nitpick at stuff that isnt supposed to be there, or is....
I was getting this on one of my backlits. Well a slight variation anyhow.
It came down to board track damage, Look around the tracks of all the tantalums you replaced and test the tracks of continuity. If anywhere on the non backlit, i would be suggesting looking around the V1M board or "HYBRID BOARD" as its known
It came down to board track damage, Look around the tracks of all the tantalums you replaced and test the tracks of continuity. If anywhere on the non backlit, i would be suggesting looking around the V1M board or "HYBRID BOARD" as its known
That also brings up another point. I seen your other thread where you replaced the capacitors, and you removed the old ones. the traces didn't look so good at all from the corrosion. Might want to do some continuity tests on those.
Also same thing with the multi-layer eyelets that connect traces on one side of the board, to the other. test those. sometimes itll break the connection between the layers from the corrosion. Ive seen this once on a car stereo faceplate that got wet. it broke the connection from the top side of the board, to a trace on the bottom side of the board because the eyelet corroded a little bit. Scraping the solder mask away on both sides of the eyelet and sticking a wire in the hole, filling it with solder, fixed the connection.
Food for thought...
Also same thing with the multi-layer eyelets that connect traces on one side of the board, to the other. test those. sometimes itll break the connection between the layers from the corrosion. Ive seen this once on a car stereo faceplate that got wet. it broke the connection from the top side of the board, to a trace on the bottom side of the board because the eyelet corroded a little bit. Scraping the solder mask away on both sides of the eyelet and sticking a wire in the hole, filling it with solder, fixed the connection.
Food for thought...
