A600 will not do a warm reset - Ctrl-Amiga - Amiga

[prowler]

That wire's not gonna break!

[kipper2k]

hehe, hope not...

cost a lot of manhours that little piece of wire, i was getting ready to give up on fixing it.

[Zetr0]

Well done Kipps!!!

I wonder what it was that ate the copper track away.....

I have not known mono-caps to damage a board like that....

[Shadowfire]

Originally Posted by kipper2k

@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

Actually, Q622 pulls U14.2 low (the 555 timer). This starts the 555 timer, which uses R612/C612 to time a pulse 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

Yes, an AND gate with inverted inputs is the functional equivalent of a NOR gate. (Just write up a logic table to see the proof.) This is not the same as a NAND gate, which is an AND gate with an inverted OUTPUT.

I know *nothing* about the A600 keyboard, but based on the schematic, I'd say that's a reasonable educated guess (the lines to the NOR gate being the CTRL/A/A lines from the keyboard). Apparently those keys have their very own switches outside of the regular matrix on the A600.

Glad to see that you found the problem, after you went ahead and replaced those IC's there's little else it could have been aside from Q622 or a bad trace. Too bad you had to do all that work before finding it.

Edit: Looks like something ate away at the copper under the solder mask. I doubt that the board would have passed Q.A. at Commodore if it had come like that from the board house. I have, however, seen some terrible PCB's come out of some of the cheaper manufacturers, where it looked like someone splashed developer on the boards during the board's manufacturing. Unfortunately, we didn't spot the 3 boards with this problem until *after* they already had been populated, and failed testing. Lots of kynar jumpering and XACTO work to fix .

Hope you saved the old IC's, seeing as they are probably all good.

[cosmicfrog]

another problem solved

[hardgb]

Originally Posted by kipper2k

Solved!!


See if you can find the bad trace.... Answer is below




Ok, look to the right of the 10uf electrolytic capacitor, there are 4 empty pads, i removed the capacitor from the upper and lower pad closest to the capacitor. look at the trace coming into the top of the lower pad... the trace coming from Q511 (currently removed) to that pad is broke. Therefore the transistor would never go low and the KB_RESET would not generate a warm reset!!



YAYYYYYYYYYYYYYYYYYYYYY!!!!!!


Thanks to all for help

Firstly, I apologize for returning to this discussion, but I have the same problem with my A600 and I don't understand the solution to the problem. The fact that you need a translator to understand English is an aggravating factor. But please, I need help getting my A600 to restart again.