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You shouldn't be seeing voltages over 5v anywhere in the logic circuits.
Test if the 7805 is producing more than 5v, or if the RAM circuit (which is on
a separate regulator) has more than 5v.
In practice I'd rarely see more than a 0.2v error from these regulators, so
there would seem to be a power issue.
Fred
In lugnet.robotics.handyboard, Patrick Schmid writes:
> Hi,
>
> I've a dead board here and don't know what to do anymore...
> The following is happening:
> I can download the pcode to the board, but when I then try to reset the
> board, the IC message won't show up on the display, there won't be any beep,
> and IC reports that I can't establish connection with the board. The LCD
> looks like there is now pcode loaded.
> I've tried the following things:
> - removed all ICs and followed the test instructions in the assembly manual.
> The first test failed was "Running the 6811 Software"
> - replaced the 6811, the RAM chip, the 74HC132, the LCD with parts from a
> perferctly working handy board. I also tried all of our parts in this
> working handy board and they worked perfectly
> - the E-clock signal looks kind of wierd after I removed all ICs. It was a
> perfect square wave with 2 MHz and 5 V with the ICs still on it, but now it
> is still a square wave but it shows a peak of 6.6V at the beginning of each
> part of the square wave.
> - I checked a lot of connections for continuity
> - all soldering still looks OK
>
> What had happened? I have no idea. I didn't use the board for about two
> weeks and now I suddendly is dead.
>
> Can anybody help me please?
>
> Thanks.
>
> Patrick Schmid
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Message is in Reply To:
 | | HELP!! Dead board
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| Hi, I've a dead board here and don't know what to do anymore... The following is happening: I can download the pcode to the board, but when I then try to reset the board, the IC message won't show up on the display, there won't be any beep, and IC (...) (24 years ago, 29-Nov-00, to lugnet.robotics.handyboard)
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