Discussion about the Korg PolySix synthesizer

Hi,

Good to know my cheapo stuff will at least be useful for the 70's and 80's stuff :)
I have just double-checked and measured (resistance check) on every pin of IC31 to different other locations and on every trace that passes under it and everything seemed fine. But just to make sure, I also patched DB0-DB3 from the CPU with wire to the pins of the IC31 socket.
Still no change in the behavior.
The original CPU socket is still there yes but I don't really feel like changing it now (and I don't have any socket at home).
I'm starting to believe you're on to something regarding the 74LS series. Maybe the HC isn't a good replacement.
Next thing I will try is to see if I can get hold of a 74HCT08 instead and see if it works better.

I will just carry on with the rest calibration for now instead. That seems to be going ok except for the first reset calibration :)
I'll let you know the results when I find a 74HCT08 to test with.

Thanks,
Peter



  ----- Original Message ----- 
  From: backshall1 (dsl) 
  To: PolySix@yahoogroups.com 
  Sent: Sunday, May 15, 2011 4:21 PM
  Subject: RE: [PolySix] Original KLM367 reset calibration. Program LEDs 2,3,4 work but won't light during calibration.


    
  For many, many years all I had was a 5MHz Heathkit oscilloscope (yes, built
  it myself) and it was just fine for things like the Polysix. The only
  drawback was it was single-trace so I eventually bought a 4-channel
  Tektronix on Ebay. You should be fine with what you've got.

  The original spec for the AND gates is 74LS08 and I believe the S is for
  Schottky diode inputs to cleanup bad input signals. The input is from the
  CPU and the peak voltage for a logic "1" from the CPU can be fairly low.
  Since you are working with damage on the data bus on IC31, chances are the
  traces to the CPU are not in good shape, which also means there could be
  considerable damage to the CPU socket. Do you still have the original CPU
  socket in there? As Andy has told me at least twice before, he always gets
  rid of the old CPU socket, cleans up underneath and puts in a new socket.
  That has fixed many strange problems for me.

  Don B.

  _____ 

  From: PolySix@yahoogroups.com [mailto:PolySix@yahoogroups.com] On Behalf Of
  Peter Mörck
  Sent: Sunday, May 15, 2011 9:30 AM
  To: PolySix@yahoogroups.com
  Subject: Re: [PolySix] Original KLM367 reset calibration. Program LEDs 2,3,4
  work but won't light during calibration.

  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 <mailto:PolySix%40yahoogroups.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
  <mailto:andy%40networkjabber.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> 
  > <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
  >> > 
  >> > [Non-text portions of this message have been removed]
  >> > 
  >> > 
  >> > 
  >> > 
  >> > 
  > 
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  > 
  > 
  > 
  > 
  > 

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