First test failed

Startbeitrag von Gunther Hoppe am 31.03.2016 09:15

The first test with the CPU unit and the base memory board light up all 4 LEDs from the base memory board. Does somebody has any idea ? Is my problem in the CPU or base memory board?


Hi Gunther,

This is very hard to say. When all 4 LEDs are lit, it means in almost all cases that the CPU is not running at all. Maybe the memory board has an error, but of the more complex CPU (five PCBs instead of one) I think you should start looking for the error at the CPU boards.

Please check:
- are all pads / connections soldered correctly? If you are using your own self-made PCBs, do you have also soldered all pads on the top side of the PCB that I have marked red in the selfbuild-guide?
- ensure that there are no shorts between adjacent solder points
- please check all ICs if the correct types are populated
- please check the EPROMs and their content, if they are programmed correctly
- check all jumper settings and start with the lowest clock frequency
- check the reset-circuit at the interface board, make sure that the CPU gets a valid reset signal and the reset gets de-asserted after some hundred milliseconds

If you are using a mixture of 74HC and 74AC logic, exchange all 74ACs by there 74HC counterparts.

von Dennis Kuschel - am 31.03.2016 11:15
Thank you for your quick response. I'll check all the points. I will provide feedback.

von Gunther Hoppe - am 31.03.2016 19:58
The MYCPU runs. The error was simple. I had inserted the oscillator in a wrong position.
I am very happy - the next step is the graphics card. :rp:

von Gunther Hoppe - am 02.04.2016 19:44
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