Hi,
The LFO Mode switch has 3 positions: VCA/VCF/VCO. This is encoded to
2 digital bits, so it is normal that in one position the switch is
unconnected.
The MG routing switch is IC1 (a 4066) on KLM-367. the LFO signal is
input on pins 1, 3, and 11 and switch by control singals at pins 13,
5, and 12. As the LFO signal may be positive and negative IC1 is
connected to +5V and -5V supply. The logic is running solely off the
+5V (and 0V of course), so there is a level translator necessary.
This is the function of IC3 (LM339). Decoding of the two bits into
3 switch signals is done at the output of IC29, the latch, which has
true and complementary outputs. D13 and R90 do this.
OK, now measure at IC1 and IC3:
+-----++-----------------++-----------------++-----------------+
| || IC 3 || IC 3 || IC 1 |
| MG || 9 | 11 | 5 || 14 | 13 | 2 || 13 | 12 | 5 |
+=====++=====+=====+=====++=====+=====+=====++=====+=====+=====+
| VCA || 0V | 0V | +5V || -5V | -5V | +5V || -5V | -5V | +5V |
+-----++-----+-----+-----++-----+-----+-----++-----+-----+-----+
| VCF || +5V | 0V | 0V || +5V | -5V | -5V || +5V | -5V | -5V |
+-----++-----+-----+-----++-----+-----+-----++-----+-----+-----+
| VCO || 0V | +5V | 0V || -5V | +5V | -5V || -5V | +5V | -5V |
+-----++-----+-----+-----++-----+-----+-----++-----+-----+-----+
I hope this helps,
Johannes
analogfuture wrote:
> Hi!
>
> My Polysix has had its screws put back in place and I've only been
> making sounds with it for a while. It mostly works more or less as it
> should. At times something happens to the signal level and something
> sounds like erratically auto-oscillating analog stages. I had this
> when I first unpacked it too and never really found out where the
> problem was, but I suppose a dirty/bad connector or a bad solder
> joint or some other intermittant connection somewhere. Of course I
> have a scope so it should be possible to find the source of the
> problem. It's definitely not in the digital section, as power down/up
> doesn't make a difference.
>
> The trickier problem I face is that the "VCA" setting of the MG MOD
> switch doesn't work - but I think it did for a very brief period.
> Both VCF and VCO settings work as they should, just not the VCA
> setting. I've studied the diagrams but it looks to me like the switch
> data from the MG MOD selector is tangled up with everything else
> that comes from the control panels (of which everything works!) so I
> need to come up with a way to pin down this problem.
> In the diagram it looks like the bottom setting of the MG MOD switch
> (set to "VCA"??) is not used electrically so I take it there's
> nothing wrong with the switch itself and that the logic on the KLM-
> 367 is meant to sort this out...?
>
> Any suggestions on how to find the problem with the "VCA" MG MOD?
>
> TIA,
>
> Thomas
>
>
>
>
>
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