STE 1040 CA401177 Black Screen.

[jorevf]

Hi,

I’m looking into a dead STe, presumable one of the last revisions.
It does not generate any screen output, and also no output is received over rs232 with the STe diagnostic cartridge inserter.

All clocks are fine, MCU generates CS for ROM and RDY pulse for DMA.
The CPU goes halt, in a blink of an eye.
And 68901 never have CS active (constant +5 )
buss error is not active.
So it seems it travels a bit, before CPU goes halted.
There is no hot circuits and PSU is fine ( tried two, and they both work in a working STe )

According to the STe field manual they say, no data on rs232 replace 68901.

My question is, how common is problems with 68901 circuit?
And does anybody have a pin diagram of the 44 pin DMA circuit ?

Any tips is appreciated..

Regards!
F

[DoG]

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