--- In
PolySix@yahoogroups.com, "synthmdl76" <synthmdl76@...> wrote:
>
>
>
> Sorry I meant board 367 not 376
>
> Im checking the TP voltages righ now, then im testing the RESET. If I
> move VR1 when the cutoff is jumping that seems to effect the jumping
>
The fun thing about the battery leakage problem is that it can do many
different things. The SIL pullup resistor near IC30/31 can go open
circuit for certain lines, the lines can go open circuit to the
microcontroller, they can go short (or effectively short for small
signals) to other lines. The short problem is the hardest to track
down and is also the reason that it's best to physically remove any
tracks that appear to have been damaged. Once the corrosion has got
into a track you can be sure it has also leaked under the protective
coating on top of the board - this causes the PCB itself to become
conductive!
If you have a 'scope you'll quickly be able to find a problem on one
of the lines that feed in and out of IC30/31.
I don't think it can be emphasised enough that battery leakage is a
tricky thing to fix if you're not already experienced in the many ways
it can mess with your brain while you fault-find. It can be quite
difficult to estimate the amount of repairs required, of the 3 I've
done the cleanest looking was the one with the most damage. If I came
across another unmodified polysix I'd remove IC30,31 and the
microcontroller's socket and replace them all with sockets, cut and
hard wire all the lines in and out of IC30,31 and perhaps the SIL
resistor and maybe do the same for the CMOS stuff beside the battery
before I even powered it on. ...or maybe I'd just rip its guts out and
work on that Polytwelve project that I keep in a dark corner of my
brain (which would be two 366s hanging off a modern microcontroller
board).