Discussion about the Korg PolySix synthesizer

I think I've finally brought my P6 back from the grave after a big
KLM367 rewiring job, and it's sounding great!  I've followed the
calibration procedure, and it now seems to be 100% functional, except
for a complete lack of effects.  Chorus/phaser have no effect at all,
and when I select Ensemble I just hear a loud repeating thumping noise.

I've checked CN03 from the KLM367, and pins 4, 5 and 6 measure 4.8V
when the appropriate effect is selected, while CN03-7
(speed/intensity) swings from -4.8V to +4.8V, depending on the front
panel pot.  Other parts of the KLM368 (headphone & output amps) appear
to be fine.

Any help would be appreciated! 

Cheers
Frank

Hi Frank,

I would venture that you may have not completed your mission with the 
KLM-367. I would go back and check the tracks and function of the 
logic at IC29 and IC34. Pay special attention to the control lines 
P24 and P24. The track from the CPU port to this pin runs directly 
along the area where the battery leaks! These two chips are 4042 quad 
CMOS latches, so testing them might require the use of a logic probe.

Once you have verified this is working OK, then we can move onto the 
effects processor board, but not until!

Let us know how you get on and if you need any further help!

Cheers,
Andy



--- In PolySix@yahoogroups.com, "Dr Funk" <frank@...> wrote:
>
> I think I've finally brought my P6 back from the grave after a big
> KLM367 rewiring job, and it's sounding great!  I've followed the
> calibration procedure, and it now seems to be 100% functional, 
except
> for a complete lack of effects.  Chorus/phaser have no effect at 
all,
> and when I select Ensemble I just hear a loud repeating thumping 
noise.
> 
> I've checked CN03 from the KLM367, and pins 4, 5 and 6 measure 4.8V
> when the appropriate effect is selected, while CN03-7
> (speed/intensity) swings from -4.8V to +4.8V, depending on the front
> panel pot.  Other parts of the KLM368 (headphone & output amps) 
appear

> to be fine.
> 
> Any help would be appreciated! 
> 
> Cheers
> Frank
>

Hi Andy

Thanks for your help!  


> I would go back and check the tracks and function of the 
> logic at IC29 and IC34. Pay special attention to the control lines 
> P24 and P24. The track from the CPU port to this pin runs directly 
> along the area where the battery leaks! 


I checked control lines P24 and P25 from CPU pins 35 and 36 to pin 5
of IC29 and IC35 (is this what you were referring to?), and there were
a few ohms of resistance, so I jumpered them.  No improvement though...


> These two chips are 4042 quad 
> CMOS latches, so testing them might require the use of a logic probe.


Unfortunately I don't have a logic probe - just a scope and DVM here...


> Once you have verified this is working OK, then we can move onto the 
> effects processor board, but not until!
> 
> Let us know how you get on and if you need any further help!


I think I need further help already! :-)  Can this be diagnosed
without a logic probe?

Cheers
Frank

Hi Frank,

No problem, we are always here to help, if we can! Actually, I do 
mean what I say. Look at the circuit diagram and carefully study IC29 
and IC34. You will see that pin 5 is connected to the ports on the 
CPU. It doesn't look like it on initial inspection, but it is true. 
Without these present no data for the effects panel will be clocked 
through.

What I would suggest is that you print out the KLM-367 circuit 
diagram, take out a coloured marker and check the continuity around 
both these ICs. As you do mark the line as checked in hideous yellow 
ink. Apologies if this is 'grandmother' and 'eggs'!

You can check the logic levels with the oscilloscpe. Sorry I didn't 
realize you had one! You could use the DVM to do this but you 
wouldn't be able to see a pulse train (rapid changing levels) using 
one.

Also you might want to fully test the continutiy of tracks D02 and 
P11, P12, P13. These actually leave the 367 and are wired to the 
switch via diodes. Sorry, it is labourious work, but one you spot the 
fault it is a joy to behold!

Question? Does the EG Mode and Sub Osc switch do anything?

Let us know your progress.

Cheers,
Andy

Hi Andy


> No problem, we are always here to help, if we can! 


Much appreciated!


Actually, I do 
> mean what I say. Look at the circuit diagram and carefully study IC29 
> and IC34. You will see that pin 5 is connected to the ports on the 
> CPU. It doesn't look like it on initial inspection, but it is true. 
> Without these present no data for the effects panel will be clocked 
> through.


These both appear to be fine.


> 
> What I would suggest is that you print out the KLM-367 circuit 
> diagram, take out a coloured marker and check the continuity around 
> both these ICs. As you do mark the line as checked in hideous yellow 
> ink. Apologies if this is 'grandmother' and 'eggs'!


No problem!  I am an 'enthusiastic amateur' when it comes to
electronics, but I've learned a lot in the past few months!  It's very
satisfying to begin to understand how my synths work.  Anyway, I've
checked continuity as much as I can, and everything seems to check
out.  I've checked IC29 and IC34 to the CPU and external connectors,
and it all seems to be ok.


> 
> You can check the logic levels with the oscilloscpe. Sorry I didn't 
> realize you had one! You could use the DVM to do this but you 
> wouldn't be able to see a pulse train (rapid changing levels) using 
> one.


Sounds good, but I'm not sure where to probe!  IC29 and IC34?


> 
> Also you might want to fully test the continutiy of tracks D02 and 
> P11, P12, P13. These actually leave the 367 and are wired to the 
> switch via diodes.


These seem to be ok too.


 Sorry, it is labourious work, but one you spot the 
> fault it is a joy to behold!


I can't wait! :-)


> 
> Question? Does the EG Mode and Sub Osc switch do anything?


Yes, both seem to be working properly.  Also, if effect intensity is
turned up full, when chorus is selected the filter seems to open up
slightly, and if phaser is selected there's a low level repeating
pulse sound audible.

Cheers
Frank

Try to check 4xxx circuits on effects board... also very popular
problem in korgs is that lm13600 got broken often. ne5517n is cheap
and good replacement for those!  :)



--- In PolySix@yahoogroups.com, "Dr Funk" <frank@...> wrote:

>
> Hi Andy
> 
> 
> > No problem, we are always here to help, if we can! 
> 
> 
> Much appreciated!
> 
> 
> Actually, I do 
> > mean what I say. Look at the circuit diagram and carefully study IC29 
> > and IC34. You will see that pin 5 is connected to the ports on the 
> > CPU. It doesn't look like it on initial inspection, but it is true. 
> > Without these present no data for the effects panel will be clocked 
> > through.
> 
> 
> These both appear to be fine.
> 
> 
> > 
> > What I would suggest is that you print out the KLM-367 circuit 
> > diagram, take out a coloured marker and check the continuity around 
> > both these ICs. As you do mark the line as checked in hideous yellow 
> > ink. Apologies if this is 'grandmother' and 'eggs'!
> 
> 
> No problem!  I am an 'enthusiastic amateur' when it comes to
> electronics, but I've learned a lot in the past few months!  It's very
> satisfying to begin to understand how my synths work.  Anyway, I've
> checked continuity as much as I can, and everything seems to check
> out.  I've checked IC29 and IC34 to the CPU and external connectors,
> and it all seems to be ok.
> 
> 
> > 
> > You can check the logic levels with the oscilloscpe. Sorry I didn't 
> > realize you had one! You could use the DVM to do this but you 
> > wouldn't be able to see a pulse train (rapid changing levels) using 
> > one.
> 
> 
> Sounds good, but I'm not sure where to probe!  IC29 and IC34?
> 
> 
> > 
> > Also you might want to fully test the continutiy of tracks D02 and 
> > P11, P12, P13. These actually leave the 367 and are wired to the 
> > switch via diodes.
> 
> 
> These seem to be ok too.
> 
> 
>  Sorry, it is labourious work, but one you spot the 
> > fault it is a joy to behold!
> 
> 
> I can't wait! :-)
> 
> 
> > 
> > Question? Does the EG Mode and Sub Osc switch do anything?
> 
> 
> Yes, both seem to be working properly.  Also, if effect intensity is
> turned up full, when chorus is selected the filter seems to open up
> slightly, and if phaser is selected there's a low level repeating
> pulse sound audible.
> 
> Cheers
> Frank
>

At long last, my P6 is alive!  Thanks to some help from Andy, for
which I am extremely grateful, the effect problem was traced to IC7
and IC8, the NE570N companders.  One of them had gone bad, so I
replaced both and the effects are working!

Cheers
Frank

Another one for the field notebook! Perhaps we should write a repair 
manual for the P6...

Merry Xmas Everyone

Andy



--- In PolySix@yahoogroups.com, "Dr Funk" <frank@...> wrote:

>
> At long last, my P6 is alive!  Thanks to some help from Andy, for
> which I am extremely grateful, the effect problem was traced to IC7
> and IC8, the NE570N companders.  One of them had gone bad, so I
> replaced both and the effects are working!
> 
> Cheers
> Frank
>