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Does anyone know the source location of the output enable (oe) pin for the G8/G3 crystal is. I have a board that was working but now the OE is always LOW on just this crystal and measuring from that pin to any of the others results in an open reading. I've checked the 9600 schematics and...

The M5126 shares the majority of the same schematics with the M5120 which can you find online and contain the video section. The key differences between the models are the ram logic and hybrid module.

As part of solving a sad mac issue on an Apple Macintosh Backlit Portable (m5126) I ended up drawing out the RAM logic which others might find useful. I've checked it twice however it's the first schematics I've ever drawn so any issues let me know and I'll make the corrections.

Just to close this, the problem ended up being a broken trace under U4G in the RAM logic. Not sure what caused it to break but it resulted in the system using the DTACK generated by the GLU rather than the replacement M5126 RAM logic thus causing the random conflict with the RAM refresh...

Thank you, that makes sense why there is a condition when no RAM gets enabled. In the case of this computer I can see when the read fails it is because a RAM refresh is happening at the same time. Are you able to explain how this is supposed to work so the two actions never overlap as I'm not...

On further investigation the logic analyzer was causing the false reading on this pin, you are correct that it's just pulled down to ground via RP4. I've gone back and confirmed my other readings, and it appears the problem is with an invalid RAM CE signal coming out of U3J (74ac138). I am...

Thanks, that sounds right as I also found the test point. I'll check my results again in case it was a false reading.

Managed to get some measurements when it fails to read correctly, and it appears it's because in that case no RAM are enabled (ie. CE is high of all 4 pairs) so the contents in the buffer doesn't change. Working backwards from this takes me back to U4G. Looking at pin 1 during a failed read...

Thanks for your suggestions. I initially suspected the 245's myself and purchased a cheap USB logic analyzer for that exact reason. Unfortunately, using the analyzer I'm not getting valid readings from the known source so either the device is either faulty or it's a software issue so I'll need...

I am having trouble sorting an issue with a friend's portable that was previous recapped by someone else and was working for years. On startup it's now getting a data bus error 000E FFFF. The board was in a bit of a state, so I've since ultrasonically cleaned it as well as repairing some...

Thank you.

Does anyone have documentation of the jumper setting for this card? Currently I have a DX4 100 CPU but on startup it says 75mhz CPU clock so I suspect the jumper settings are incorrect. I found references to a site "Andrew's OrangePC 290 page" which had this information however the site no...