Macintosh Plus... Another Analog board issue

[bibilit]

I have a Plus with a strange issue.

The Plus will no boot, no chime is present, but will display black and white vertical stripes.

The problem is not coming from the Logic Board, tested in another Plus, the LB works fine.

Testing this Analog Board with another Logic board displays the same pattern, so pretty sure the Analog is the problem.

Have not tested outputs yet, swapped the ribbon connecting Analog and Logic...same result.

usual weak spots have been welded back.

 

[apm]

Check the voltages? Especially 5V. The CPU may be more sensitive than the display logic.

 

[bibilit]

Yes, as said before, suspecting a problem in this area, will check soon.

thanks.

 

[bibilit]

Problem solved.

Outputs were a bit weak, replace the Optoisolator H11AV with a spare and working great.

Should order a few of those... where do you get this item ?

 

[bibilit]

tested yesterday after a message from Ferrix97, can be replaced with reference CN17.

No problem with this cross reference.

Also solved the Flup-Flup problem in another AB, same part (optoisolator)

 

[just.in.time]

What exactly does this part look like, and where is it located on the analog board?

 

[bibilit]

On the bottom left section of the board, label is U3 on mine, looks like a square black part with 3 legs on each side.