Macintosh IIsi blue screen - need help

[9166188]

Just replaced the 2 big caps of 220uF as well.   So, all caps onboard are new now.   No luck still.

I did connectivity test between each leg of the caps to a nearby joint by following lines onboard.   Is this good enough?

Before throwing my towel, I gave another good wash to the board.   Almost no residue came out.  It's now very hygienic.

But the problem must be something else in the logic board.  But I don't know exactly what can be done next.

 

[9166188]

I suspect DZ1 because diode test on my multimeter shows .54 on one side.  My amateur reflex thinks DZ1 (should as nearby DZ2), shows an OL reading when I switches the probes.   But DZ1 surprises me with a .99 reading.   I know I shall really take the diode out to be accurate.   But this is by me who doesn't know fully what he is doing.  

 

[techknight]

Yeap your chasing a 3 ring circus here. 

I think the actual problem is likely to be a corroded or open trace/via. its common in the areas where the caps had leaked. 

 

[9166188]

Great advice!   Will keep looking for broken trace under the bush.   I have spent so much time on this now.   The sunk cost has driven me addicted in finding the culprit!

 

[Elfen]

I got a IIsi from ebay.  It shows a blue screen on a 13" Apple High Resolution monitor when powers on.

That's it, a blue screen? No video, no raster, no icon, no boot screen?

I would agree with TechKnight on a rotted trace by a cap. Here is a trick I learned from the Arcade Machine Restoration people - use a black UV Light and look at the traces with a magnifying glass. The traces will "glow" brighter and a dead trace will look "darker."

[warning = Tech Rant]

If this would have been a VGA Monitor, and not an Apple RGB Monitor, this would have been fine. Both the IIsi and the IIci have this blue screen issue with some VGA Monitors, but they boot up an everything, though blue, does work and you get a desktop with the mouse working. You would have to play with the monitor settings for 640 X 480 @ 16 colors and then play with the adapter. Sometime this fixes the problem, most of the time it does not. Can't win all battles.

The problem is that you are using an Apple 13in RGB Monitor. That creates a different set of problems to try to figure out.

Q: Does the monitor works fine on other Macs? I'm hoping that it does. It would be a rabid female dog to find out that you are chasing a IIsi video issue and the problem is actually with the monitor or its cable.

[/warning]

Good luck. Let us know what you find.

 

[9166188]

Thanks for the new input.   Haven't tried it for a while.   

To be clear, the 'blue' screen is a very very dim blue screen.   i.e. one cannot even notice under normal lighting.   I only got noticed it was a 'blue' screen by chance after switching off all lights in my room.   So, u see how dim it really is.  I also tried paired it with a LCD PC monitor, but nothing comes all.

Fundamentally the problem is the death of chime sound.   The blue screen is likely only a side effect of something in the motherboard.

By now I know the 4MB RAMs are good because I put them on another Mac and they work!

 
I've traced most of the lines and they seems ok with connectivity test.   The way I did it is by taking snapshots on my iPad, and magnify from there to trace their endpoints. 
 
Your suggestion of using UV Light is interesting.   Do u know why [The traces will "glow" brighter and a dead trace will look "darker."]?    I like to give it a try also.
 
Thanks again!

 

[techknight]

the blue screen now that you explain it, is totally and completely irrelevant. Throw that idea out in file 13. 

Your issue is failure to boot. if its chimes of death then it likely cannot see the RAM. 

if the logic board isnt fully recapped that WILL be a problem. if it is, its a broken trace as I have explained on several occasions.