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Intermittent problem with sound and sound selection

Intermittent problem with sound and sound selection

2016-11-26 by josh.nursing@gmail.com

Hi all,

My Polysix does this on turning on: Sound A1 is selected but the sound played is a sound changed from what I have saved in that location. Additionally, if I select a new sound, let's say A2, both A1 and the 2 LED light up.

It does the same thing if I select B2 right after turning on: both A and B light up and both 1 and 2 light up.

Now, I know this is an intermittent issue because after a good while of letting the Polysix dormant, I opened it up, checked all the boards and cabling, turned it on and had normal operation and sounds for around 25 minutes until the sound sort of fizzled out to that weird state.

Since I had repaired KLM-367, it could well be that the insidious battery leakage creep is ongoing. Does the issue above sound familiar? Does anyone know where I could focus re-checking things and fix it?

Thanks a lot, and have a great week-end!

Yash


Re: [PolySix] Re: Intermittent problem with sound and sound selection

2017-05-11 by Peter Mörck

Without giving any particular advice, I'd say your initial hunch about battery leak damage is most likely correct.
Check the ICs right next to where the battery was. IIRC there are a lot of address demux ICs there, and it those traces are damaged, or the chip it self, all kinds of weirdness happens, which is probably why the battery leaks tend to lead to all kinds or bizarre problems. Like IC 30 and 31.
Check the traces for continuity.
Check vias for continuity.
Traces also run under the ICs so there could be damage you won't see until you remove the chip. Damaged vias are obviously difficult to see as well.

On 11 May 2017 at 17:47, josh.nursing@gmail.com [PolySix] <PolySix@yahoogroups.com> wrote:
 

No one at all?


Could it be a grounding issue?


Re: [PolySix] Re: Intermittent problem with sound and sound selection

2017-05-11 by Peter Mörck

Woops, IC30 and 31 are "buffers", but of course if they are not working properly it also causes funny stuff.
Likewise IC 23 and 25 that handle chip select signals probably cause problems if damaged as well...
Guess that goes for most of the components in that area though. So.. Check the surroundings again :)

On 11 May 2017 at 20:01, Peter Mörck <peter@morck.info> wrote:
Without giving any particular advice, I'd say your initial hunch about battery leak damage is most likely correct.
Check the ICs right next to where the battery was. IIRC there are a lot of address demux ICs there, and it those traces are damaged, or the chip it self, all kinds of weirdness happens, which is probably why the battery leaks tend to lead to all kinds or bizarre problems. Like IC 30 and 31.
Check the traces for continuity.
Check vias for continuity.
Traces also run under the ICs so there could be damage you won't see until you remove the chip. Damaged vias are obviously difficult to see as well.

On 11 May 2017 at 17:47, josh.nursing@gmail.com [PolySix] <PolySix@yahoogroups.com> wrote:
 

No one at all?


Could it be a grounding issue?



Re: Intermittent problem with sound and sound selection

2017-05-11 by josh.nursing@gmail.com

Hey Peter, thanks for your reply.

Good point about that Demux area. I have done a lot of work in that specific area a good while ago with the help of several cool people on this group and managed it, new chips, new traces and so on.

It's definitely worthwhile to re-check that again. I just know it took me a very long time when I did it, but I should be able to do a check faster this time.

The reason I thought of a potential ground issue is that there is in the default configuration, a GND lead which is soldered onto KLM-367. However, this makes it hard to work on the synth in stages as you need to solder and de-solder this each time, so I added a jumper which makes the connection easy to do and remove when opening the synth. 

However, a jumper isn't very robust, so that's why I am thinking it could be intermittent here, possibly being pulled apart a little, breaking connection sometimes, sometimes making it when the faceplate is closed.

I'll try and make it a more robust joint and see if that helps. If it doesn't, it's off to checking KLM-367 again :D

Re: Intermittent problem with sound and sound selection

2017-05-12 by josh.nursing@gmail.com

So yesterday, I hauled up the Polysix on the workbench and checked this: the hardware jumper connection itself appeared to be robust. However, and I had forgotten about this completely: the junction between the GND Wire coming from the middle upper PCB to the hardware jumper wasn't secured at all. This was OK for a one-shot testing, but since there's no solder even, it would move around.

I fixed this by removing all wires and using two new ones with robust connectors.

Tested it, and there's definitely an improvement, now the Polysix turns on with no blinking LEDs and seems more stable.

There's another issue now: I cannot get the Patches recalled. On the other hand, right before my mods yesterday, I did manage to get them all at one point. So that means, the battery is still OK, the memory is OK, but now, for some reason, the patches aren't loaded.

Any ideas?


---In PolySix@yahoogroups.com, wrote :
 so I added a jumper which makes the connection easy to do and remove when opening the synth. 

However, a jumper isn't very robust, so that's why I am thinking it could be intermittent here, possibly being pulled apart a little, breaking connection sometimes, sometimes making it when the faceplate is closed.

I'll try and make it a more robust joint and see if that helps.