Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

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Subject: Re: [PolySix] I killed my PolySix

From: Bob Grieb <bobgrieb@yahoo.com>
Date: 2014-04-29

The LEDs that you say are working are controlled by the key assigner MCU.
The other LEDs are controlled by the MCU on the KLM367 bd.  Can you get into
the DAC calibration mode by flipping the switch on the KLM367?   At least that would show that the MCU is executing code.  (I'm not suggesting that you calibrate the DAC, just see if the CPU will enter that mode)  Do you have an oscilloscope?   The 4.2V value seems low.  How much confidence do you have in your DMM?

Many of the chips you are probing are analog, and have power on different pins.   Please
just focus on the digital IC's.   Maybe you need to download the service manual and take a look at the schematics?   Usually the problems with the KLM367 have to do with IC31, 30, and connections to the front panel on CN06.   If you have a scope, what is the waveform like on pin 32 of IC22?   (Be careful not to short to an adjacent pin when probing)

    Good luck,

        Bob


From: "jeremy.pisani@gmail.com" <jeremy.pisani@gmail.com>
To: PolySix@yahoogroups.com
Sent: Monday, April 28, 2014 6:56 PM
Subject: [PolySix] I killed my PolySix, help!

 
So, I did a stupid thing. I got my PolySix a few years back, and it had the leaky battery issue. I sent the board off to be fixed by Old Crow's synth shop, and after that it was working great, except for the buttons being finicky, and the Hold button didn't work at all. After a lot of procrastinating, I finally ordered some new switches and went to work desoldering & replacing the buttons. 

At first I checked to make sure the synth was still functioning correctly after I replaced each button, but after 5 or so I felt confident enough to keep going without checking (I'm kicking myself as I write this). When all was said & done I powered it up and it's behaving like it did when I first got it. When powered on, the Write & Manual buttons light up, as well as the Bank C, Poly, and Program 3 & 5-8 buttons. I can switch between Poly/Unison/Chord Memory & Hold buttons with no problem, but it doesn't affect the sound. None of the knobs seem to affect anything either.

 I did a lot of the desoldering without putting something over the circuit boards to protect them from solder flecks, and I'm guessing maybe something got fried when I powered it on, but honestly, I don't know. I did a little poking around with a multimeter & got the following results:

Power supply voltage: 
4.2/-4.2
14.6/-14.6

All ICs on the KLM-376A are reading 4.8v except for the following:

IC14: 3.5v
IC20: 3.6v
IC21: 4.1v
IC25, IC32: 4.1v
IC34: 4.6v

Continuity between the previously repaired traces seems to be fine. Any ideas?