Yes, the old blue 40-pin socket was still in there. Removed it, did a thorough cleaning, put in a new socket, and things are running much better. The resonator resonates with good stability and several of the signals from the CPU seem much cleaner. I've got another Polysix here with a similar problem so I'll have to find another 40-pin socket to try on that one. I finally got a capacitance meter but maybe I won't need it.
Don B.
--- In PolySix@yahoogroups.com, Andrew Jury <andy@...> wrote:
>
> Hi Don,
>
> Of course the resonator is connected across pins 2 and 3 of the 8048. If you
> have a spare it might be worth seeing if how it behaves with an alternative
> connected. Also, if you still have the old blue 40 pin holder on this board
> check very carefully that there is no hidden contamination beneath it. When
> the wire link repairs were in vogue I would always replace the holder as a
> matter of course. Just a thought...
>
> Cheers,
> Andy
>
>
> On 28/05/2010 02:46, "longenough2002" <backshall1@...> wrote:
>
> >
> >
> >
> >
> >
> > Thanks to Andy for clarifying the difference between the ceramic resonator and
> > a crystal. If I had gone looking for a replacement, I would have purchased the
> > wrong part for sure. I did move a resonator from another board to this one,
> > and this board still has the problem. Sometimes it just flatlines for a few
> > minutes after being turned on, then seems to resonate just fine. I replaced
> > the 22pf and 10pf capacitors and now it resonates immediately but is fairly
> > unstable. Actually, I didn't have a 22pf so I used a 20pf. So..... I ordered a
> > bunch of tiny capacitors and now I guess it's also time to invest in a
> > capacitance meter of some sort so I can see what I'm really sticking in there.
> >
> > Don B.
> >
> > --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> , "grantpbt"
> > <grantbt@> wrote:
> >> >
> >> > Both the crystal and capacitors have characteristics quite important to
> >> achieving god oscillation, especially in the old days. ;-) Make sure all the
> >> values are spot on and that the crystal is of the correct type/cut. You
> >> should be able to use the crystal from the old board using normal desoldering
> >> techniques. Hope the old crystal is functional. Also be careful of too much
> >> flux or other contaminants in osc area.
> >> >
> >> > The scope will probably show a weak sine wave only. I don't have a Polysix,
> >> so I'm just speaking in general terms here. Where you should see a decent
> >> square wave is on the address lines (as low order as you can get without
> >> running into the data lines if they are multiplexed on this CPU).
> >> >
> >> > GB
> >> >
> >
> >
> >
> >
> >
>
>
>
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>