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Subject: Re: [PolySix] some defects after battery leak

From: Bob Grieb <bobgrieb@yahoo.com>
Date: 2015-05-15

The MCU converts controls in a round-robin sequence to determine
their position.  If the signals that select which control is being measured
are messed up, the MCU could be measuring the wrong control, which could
cause changing filter cut to affect resonance, for instance.

I would make sure the digital signals that control the muxes on the front panel
boards show low resistance all the way from the source chip on the KLM367
to their destination.  Better yet would be to look at them at the destination
with a scope, but a resistance check should also be OK.

You can test front panel scanning separately from CPU+DAC controlling the
parameters.   Use a computer to load patches into the synth with the cassette
interface.   Try the patches and see if they sound reasonable.   If so, then the
DAC is working and the CPU can control the parameters properly.

If all of that checks out, then the problem would be with the front panel
control muxing.   The DAC must be OK.

Bob


 


Sent: Friday, May 15, 2015 6:35 AM
Subject: Re: [PolySix] some defects after battery leak
 
 
I tested all sugested data lines and they all are okay. One remark : datalines D04-D07 have to be tested to IC30, IC24, IC33, IC29, IC35) and not IC34; there is a faulty diagram of KLM367 on the internet .
The problem still persists. I doublecheked the powersupply and all voltages are okay. So does anyone here have another suggestion? I think it's mainly the VCF that causes all the problems. turning cut off, resonance or KBD track changes the sound from good into a growling sound. Also the ensemle gives growling sounds when turning phase or ensemle too low or too high.
 
 
regards and thanks in advance
From: "backshall1@bellsouth.net [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Thursday, May 14, 2015 6:38 PM
Subject: Re: [PolySix] some defects after battery leak
 
 
Most of the damage is usually on the eight data lines (D00-D07) and that includes IC30 as well as IC31. The best way to test these is to use the ohm meter to test continuity from one starting point to all the other places these lines are connected. From a suggestion from Andy Jury a long time ago, I usually test from connector CN10 to all the other chips. This can be a bit tedious. D00 is pin 4 on CN10, and needs to be tested to IC31, IC26, IC33, IC28, IC34, then do the same set of tests for the other seven data lines on CN10. Alternatively, you could start from IC31 pin 6 and test continuity to IC26, CN10, IC33, IC28, IC34. When you get to D04-D07, it will be a different set of chips (IC30, IC34, CN10, IC29, IC35).
 
Don Backshall
 


Sent: Thursday, May 14, 2015 12:13 PM
Subject: Re: [PolySix] some defects after battery leak
 
 
Thanks for the reply. I repaired traces that were broken and I checked if there was continuity between traces that should not be connected to each other. I did this only for IC 31 maybe I will take a wider aerea to check on continuity. The weird thing is that most things work as they should and then when you turn one knob several parameters are changed and not only the one you turn. I put it in manual mode so all knobs function as they are set and then I can get some rather good sound but for example when I then turn the resonance of the VCF a bit then other parameters seem to have changed....any other info? I replaced the IC31 and put it on a socket. Could it be that another IC is defective when I have this strange behavior or do you think this is mostly a result of the corrosion?

Thanks again for the reply
 

At 14-mei-2015 17:13:41, 'Chromatest J. Pantsmaker' chromatest@azburners.org [PolySix]PolySix@yahoogroups.com'> wrote:



 






There are two things (well, more than that actually) that the corrosion will do that we need to pay attention to.
 
First is the broken trace, or lack of continuity. You've checked this with your meter.

Second is the shorted trace, or too much continuity. By this I mean that a trace can have continuity to a trace next to it. That would cause the signals to affect each other. When you check continuity on the traces, it's important to not only check 1-1, 2-2, 3-3 (and so on) but also to check 1-2, 1-3, 2-3 (and so on) You want all of the 1-1, 2-2, 3-3 traces to have continuity, and you ∗DON'T∗ want the 1-2, 1-3, 2-3 traces to have continuity unless they are actually connected via the schematic.