Hey Andy,
Thanks for replying.
I have a crappy Velleman-multimeter and a slow 5MHz USB scope (Picoscope) but I hope I've got enough equipment to measure what I need.
I thought the the ICs driving the LEDs were just getting old and tired since the LEDs were the only things that didn't seem to work.
But since you hinted there might be more problems with the data bus I went back to check around IC31 again. I noted that if I pushed it down real hard some more LEDs would light. Also, I am getting weird outputs from it, as if the AND-gates are not working.
On pins 1,2,3 (1A,1B,1Y) I sometimes read high, low, high. That's not right.. Also, it's enough if I touch the probe with my finger to change the reading. Smells like CMOS floating input (I have a 74HC08 there) ... or at least some faulty connection...
Blah. I guess I'm just going to take the board out and patch even where checked that it was OK.
Thanks :)
/Peter
----- Original Message -----
From: Andrew Jury
To: PolySix@yahoogroups.com
Sent: Sunday, May 15, 2011 11:08 AM
Subject: Re: [PolySix] Original KLM367 reset calibration. Program LEDs 2,3,4 work but won't light during calibration.
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 O371. If you have logic
state on the data lines work backwards towards the address decoders on the
O367...
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 O367. Do you
> have a logic probe? Shunt the test point with a 56K resistor on the PSU,
> turn VR1 on the O367 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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