X68000 Expert don´t get image

Started by Sebastian77, March 28, 2023, 01:07:47 AM

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I´m having a problem with my X68K Expert , when I turn the back switch it´s turn on, the fan spin get the green light but dont turn red and fan keep spinning. Tried to replace C264 , IC228 , 229 check R254 OK . But what I´m in doubt is theses chips (IC228 IC229) are receiving 1,28 instead 5v is that normal?



My first thoughts are the power supply.
What are you using?

When I was building my ATX adaptor I did not build the correct 'power on' logic so the system was not getting the full 5v.


The power supply was replaced by an ATX , all voltages are correct , 5v 12v etc. Yesterday I was checking the IC209 TL7705CP wich a think is the responsible for check voltages and reset if not correct, pins 2 and 8 seems to be in short but I´m not sure if it´s normal or not.


Hi! I have the same problem, I am now working to solve it, in the post


It appears that transistor Q9 can also fail. A friend who had a similar standby problem with an ACE, solved it by replacing both 74LS and the transistor.
I'm still working. Sebastian, have you been able to solve it?


Yes, solved couple days ago!

Changed the 74LS244 (IC229), 74LS08(IC228) and transistor Q209 , but still don´t turn on , then I discovered that the was a problem with the power connector too , +5vsb was not connecting properly to the board. After that is working fine! Then I made a complete recap that took me a lot of hours !!

The power connector was kind tricky , because I was  measuring +5v on upper side of the connector and was OK but there was no voltage on the IC229, IC228 and others chips on the line, after check the entire line discovered that the connector was firmly conected on the board but inside it there was no connection at all.


Sebastian77, Thanks for sharing your experience!