Star Wars trouble

Hello guys,

I have a sick Empire Strikes back boardset that has me cornered. I have already
spend weeks to find the problem but the board is smarter then me... :)

Anyway, this is what is happening:

The self-test telle me the main program ROM is bad. Replacing it does not fix it
ofcourse. I replaced it by one that tested good (from the AVG section) (BTW
Clay, do you still sell these chips?)

Then I checked all the data and address lines, they were all pulsing.

Checked the buffers by comparing the Input against the Output of each address
line with a 1241 logic analyzer, this seems okay as wel.

Checked the address decoder with the 1241, verified the RAM select line against
the A11 - A15 address lines. When the appropriate address range shows up
(4800-4FFF, 0100 1xxx xxxx xxxx) The RAM does get selected.

Anyone has a clue what to check next?

BTW, I use the rising edge of the 'ECLKQ' 1.5 MHz test point at the board to
clock the 1241. Is this right (I have head sometimes that there are 2 'phases'
on which the data is accessed and available. Could someone clear this a little
more out for me please?)

Kind regards,

Mendel
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Received on Thu Oct 12 17:58:34 2000