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pluto63

Help repair a 130 XE

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I need some help and a fresh view on a 130xe repair, at present time video out is dark red screen. When I got the board found that someone attempted to socket the OS destroying a good number of vias, I restored the damage and checked all the connection. I then socketed all major ic and ram.

Now all ic are checked working on another board, what Im getting is all data lines stacked high. Im getting a pulse at startup or reset and then they stack high. Removing the cpu and checking lines am getting a LOW signal probe on pin 30 that is data line 5. Ive checked multiple times all the D5 trace on the pcb and could not found anything wrong. Below a video with scope and board photos.

Any idea on what to try is welcome. Not recapped yet but I dont see how a dry capacitor could affect D5.

 

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post-43735-0-49838100-1558430744_thumb.jpeg

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Already checked schematics multiple times, thank you, and a small correction to my first post the Data Lines are stacked Low not High 3-4 seconds after power on or reset.

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All ic checked working, also recapped but no changes.

If “all ic” includes the 74-series logic chips, then you’ve either got a short on the board somewhere or a bad socket. There aren’t really any other things it could be.

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All ic checked working, also recapped but no changes.

 

You didn´t mention (in the text), which signal this is:

 

post-15670-0-25038500-1558528797.png

 

When the alignment of 0V is the same as the first signal you showed, then this signal is bad in any way. It looks like it never goes below 2 volts, but for a clock signal it should be.

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Signals are pin 29 ok, pin 30 not ok, and pin 31 on cpu socket ( with no cpu inside). That is the Data 5 line that I’ve checked countless times for shorts, solder blobs or anything else. Anyway i’m done with this board, it needed a fresh view so I send it to Bas to continue tinkering with it. Will update with his findings.

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The board has nicks as well as butchered pads and traces, I would look for more of the same.... double check the repairs that are already done and trace out with a dmm that traces under sockets etc are still in good shape. Looks like an errant solder flake or two as well

Edited by _The Doctor__

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