Quote:
Originally Posted by Shadowfire
Heh, I should read the whole thread before commenting.
When you press CTRL-Am-Am, check for the following things:
U36.12 rises to >=.6V (note it will be easier to check this at R623).
Q622 actually drives the 555 trigger input low (Q622.3, maybe easier to check at R611).
As you've already replace U36 and U13, it would appear you have a dead Q622 or trace damage on the board.
If I had to guess (and this is pure conjecture) the Keyboard IC is detecting CTRL-A-A, and asserting PA7 low, then running in an infinite do-nothing loop (assuming that it should be hard reset by the system _RST line).
It then probably has an internal watchdog timer reset, and comes back online.
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@Shadowfire.
I changed out Q622 and no go. I am looking at that part of the schematic and i see that the KB_RESET is triggered by Q511.3. Question is, when that transistor is on, does it dump to ground causing a low to appear on the KB_RESET line
Also i notice that there are 3 inputs from PB2, PB3 and PB6 that feed into the triple input NAND 74F27 (hmm, just noticed that when i do a search for the 74F27 it shows as a triple NOR, my schematic shows a AND symbol with the circles on the input that indicates its a NAND?). are those the raw Ctrl, L Amiga and R Amiga inputs from the membrane?
I still have to do the meter checks later tonight (Have to get the missus to hold down the keys for me while i get a read
Thanks for your help
edit... Does anyone have the Membrane schematics, i don't have that part of the schematics ?