Ooh and I forgot to mention make the measurement on the data bus as far away
from the source as possible, i.e. At IC4/5 on the 371. If you have logic
state on the data lines work backwards towards the address decoders on the
367...
Byeee!
A
On 15/05/2011 09:50, "Andrew Jury" <andy@networkjabber.com> wrote:
>
>
>
>
>
> Hi Peter,
>
> I¹d say you still have some data bus chaos going on with the 367. Do you
> have a logic probe? Shunt the test point with a 56K resistor on the PSU,
> turn VR1 on the 367 so that at least some of the LEDs come on. Then, using
> a logic probe, scope each of the data lines D0-D7 and write you result down
> in your next post. Don¹t have a logic probe? Get yourself one. You will find
> it no end of uses for it if you are going to maintain your Polysix!
>
> Cheers,
> Andy
>
> On 15/05/2011 01:10, "Peter Mörck" <peterm@sunsetselection.com
> <mailto:peterm%40sunsetselection.com> > wrote:
>
>> >
>> >
>> >
>> >
>> >
>> > Hey group!
>> >
>> > I have been recapping an old Polysix which was given to me for free in
>> pretty
>> > bad shape. I have repaired some 3 bad traces under IC31 on the CPU board >>
and
>> > also an odd corroded trace on the effects board. IC31 was removed and
>> replaced
>> > with a socket and a 74HC08. The switches on the panel are replaced and all
>> > electrolytic caps are replaced.
>> > I have removed the old battery and just put 2 wires in (insulated in the
>> ends)
>> > until I have a Li-battery to put in, which I will place away from the board
>> on
>> > a small separate board :) I also removed C40 and replaced R91 with a 1N4148
>> in
>> > preparation.
>> >
>> > Except for the keyboard which needs a good cleaning and fixing, everything
>> > responds well, I mean all the controls, write to memory, banks, programs
>> > (haven't tried tape interface though). So as far as I can tell, it is fully
>> > operational (except keyboard).
>> > So I thought it was time to run the calibration since I've replaced a lot
>> of
>> > capacitors and it doesn't track well, plus one voice is a lot louder than
>> the
>> > others.
>> >
>> > I run into "problems" right from the start. After attaching the 56k
>> resistor
>> > and turning the Polysix on I adjust VR1 on the CPU board.
>> > Bank A LED and Program 1 LED on... I turn... Program 5, 6, 7 and 8 LEDs
>> light
>> > up, but NOT program 2,3 and 4.
>> > I know the LEDs work, I've switched around before, I've saved to Bank A
>> Prog
>> > 2. Everything looks fine, but those LEDs won't come on during this
>> > calibration. Seems very strange to me. Anyone have any ideas?
>> > I even see LEDs 2,3,4 blinking very briefly sometimes if I turn VR1 back >>
and
>> > forth across the point where all LEDs should light up.
>> > Oh, and the LED on Key Assign Mode are a bit inconsistent in their behavior
>> > when the LEDs switch when I reach the proper calibration point. Sometimes
>> > another one lights up, sometimes three of them.
>> > Also the bank LEDs don't change. Only bank A LED is on but I've seen Bank D
>> > LED blink briefly as I cross the "calibration point".
>> >
>> > I measured across the zener D2 and I get 3.54V when I have 4.99V on the 5V
>> > rail. I would expect that can be affecting the calibration point but I find
>> it
>> > hard to imagine it would keep program LEDs 2,3,4 from lighting up.
>> >
>> > The machine seems to work find but obviously this seems to indicate some
>> > fault.
>> > I think I will continue with the calibration procedure anyway and hope it
>> will
>> > work out ok.
>> >
>> > Anybody have any ideas why not all LEDs light up???
>> >
>> > Thanks for reading my wall of text :)
>> >
>> > /Peter
>> >
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>> >
>> >
>> >
>> >
>> >
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