Macintosh Classic II blank screen after recap

[mitchW]

Compared diode mode measurements and found no big differences.

I discovered that the SCSI chip is actually a combo SCSI/serial IC. Here is the datasheet: http://www.datasheets360.com/pdf/-7619436183003849492

Perhaps I have a problem with a serial interface and not with SCSI.

There are also two AM26LS30JC chips, as I remember they are serial port drivers... could there be a problem?

 

[mitchW]

Here is the video again: https://drive.google.com/file/d/0BwxZGDrs2qiFSXgwTlMwdnczVzg/view?usp=sharing

I ran out of space on dropbox...

 

[techknight]

unlikely. 

 

[mitchW]

At this point I really don't know what to look else. I will do diode checks again tomorrow, maybe I missed something. I hope that it is not the main VLSI chip, as I don't have a donor board that has another one, and I am not taking it off from another working Classic II board.

Well I guess the murphy strikes this time, as I recapped about a dozen boards for a buddy of mine, and they all sprang into life with minimal initial glitches. But I bought this machine for myself, and paid quite a lot for it, so no wonder I have so much trouble  : .

I am thinking of buying another logic board, it doesn't need to be recapped or even tested, but these boards are rare, especially here in Europe.

So close... but still so far away...  :-/

 

[Elfen]

At this point I really don't know what to look else. I will do diode checks again tomorrow, maybe I missed something. 

These past couple of days had me thinking that this could be a shorted out diode or transistor on the board pulling down the reset line. One can never know until they try. Right?

Good luck to this. I hope you get it fixed. You are so close to getting it done.