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Re: front panel and ring mod-ish weirdness

2012-08-12 by tonezone020

Hi,

If you set the Delay and Level to zero does the ring mod change ?

Btw, I'm in London, where are you based ?

Regards,
Tony

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--- In PolySix@yahoogroups.com, Eric Frampton <eric@...> wrote:
>
> Hi all -
>
> I've just finished doing the standard battery damage control on my PolySix, but some weird things are happening. On this machine, it was far enough gone that I had to replace both IC30 and IC31, and do a fair amount of point-to-point wiring underneath. That said, I'm still seeing some misbehavior.
>
> First off, the entire front panel oscillator section is non-responsive to knob movement, including the Sub Osc switch.
>
> Also, the MG Mod destination is routed to VCF, no matter how that switch is selected.
>
> Next, I've noticed a weird ring mod-sounding modulation on the very end of the release stage of any notes. As best I can figure, it's the filter, not the VCA, that's being modulated at high frequency, as playing with filter cutoff/key amt/env amt changes the amount of this modulation. It's definitely not the LFO bleeding through anywhere - LFO speed has no effect on this audio-rate mod I'm hearing.
>
> Everything else seems to be working fine.
>
> Probing the A/B/C inputs of the 4051's and pin 5 of the 4042's in the KLM-367 board, I'm seeing no signal on P20 and a weak signal on P21 at the 4051's, and no signal at P24 on that set of 4042's (P25 on the other set is fine). I understand just enough to have gotten that far, but am not sure where to take it from here.
>
> So I submit my weird P6's behavior to the pro's - any thoughts?
>
> Thanks,
> Eric
>

front panel and ring mod-ish weirdness

2012-08-12 by Eric Frampton

Hi all -

I've just finished doing the standard battery damage control on my PolySix, but some weird things are happening. On this machine, it was far enough gone that I had to replace both IC30 and IC31, and do a fair amount of point-to-point wiring underneath. That said, I'm still seeing some misbehavior.

First off, the entire front panel oscillator section is non-responsive to knob movement, including the Sub Osc switch.

Also, the MG Mod destination is routed to VCF, no matter how that switch is selected.

Next, I've noticed a weird ring mod-sounding modulation on the very end of the release stage of any notes. As best I can figure, it's the filter, not the VCA, that's being modulated at high frequency, as playing with filter cutoff/key amt/env amt changes the amount of this modulation. It's definitely not the LFO bleeding through anywhere - LFO speed has no effect on this audio-rate mod I'm hearing.

Everything else seems to be working fine.

Probing the A/B/C inputs of the 4051's and pin 5 of the 4042's in the KLM-367 board, I'm seeing no signal on P20 and a weak signal on P21 at the 4051's, and no signal at P24 on that set of 4042's (P25 on the other set is fine). I understand just enough to have gotten that far, but am not sure where to take it from here.

So I submit my weird P6's behavior to the pro's - any thoughts?

Thanks,
Eric

Re: front panel and ring mod-ish weirdness

2012-08-12 by eframp1

There's no change, and the LFO modulates (as of right now only) VCF cutoff at a separate (and changeable) frequency than this sort of ring-mod thing I'm hearing.

e

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--- In PolySix@yahoogroups.com, "tonezone020" <swamp.gigs@...> wrote:
>
> Hi,
>
> If you set the Delay and Level to zero does the ring mod change ?
>
> Btw, I'm in London, where are you based ?
>
> Regards,
> Tony

Re: [PolySix] Re: front panel and ring mod-ish weirdness

2012-08-12 by klosmon

Hola Eric --
When the front panel switches aren't responding, first check the four 
ICs that handle these functions.
On the KLM-367 schematic, they are ICs 28, 29, 34 and 35 -- all 4024s.  
IC 29 outputs C, D and E are the first controls for modulation 
switching;  check that IC29 is receiving the four data lines listed on 
the schematic, and that both IC28 and 29 are receiving the P24 signal 
from the CPU (this line is commonly damaged on battery-leak boards).
Similarly, check the P25 line to ICs 34 and 35, if there are other 
switching functions not present.

If these traces are good, and you see output response from this chip 
when you move the modulation select switch, then you have to check the 
C, D and E lines to IC 2 (incorrectly labelled IC3 on the schematics), a 
339 quad comparator, which sends the control signals to the 4066 
switching IC that routes the LFO to the various destinations.

Follow the schematic...
~GMM

On 8/12/2012 1:17 PM, eframp1 wrote:
>
> There's no change, and the LFO modulates (as of right now only) VCF 
> cutoff at a separate (and changeable) frequency than this sort of 
> ring-mod thing I'm hearing.
>
> e
>
> --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>, 
> "tonezone020" <swamp.gigs@...> wrote:
> >
> > Hi,
> >
> > If you set the Delay and Level to zero does the ring mod change ?
> >
> > Btw, I'm in London, where are you based ?
> >
> > Regards,
> > Tony
>
> 

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