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

Hi list,

Sorry, long post about 2 problems: reset calibration and CHD MIDI kit.

I have two separate problems with my Polysix.
It's got an original (late production) KLM-367 board with repaired acid damage and the synth works perfectly.
Except:

The first problem is about the reset calibration and is unrelated to the CHD MIDI.
When performing the Polysix calibration routine (with or without the CHD kit, doesn't matter),
I get patch 1 LED on at first (as normal), and when I turn the reset calibration trimmer clockwise, all LEDs are supposed to light up.
However, patch LED 1 goes out and only patches 5-8 light up. LEDs 1-4 are off. Uh...
I traced the levels backwards and the problem is seen all the way back at the 8048 on KLM-367.
DB0-DB3 are low while DB4-DB7 are juuust above 1V, I guess still enough since the LEDs do light up.
A while ago, as part of battery acid damage repair, I replaced IC31 with a 74HC08 (instead of 74LS08) and the synthesizer works perfectly otherwise. I can play, save patches, all buttons and LEDs work. I don't think IC31 is the problem though as the levels are wrong already at the 8048. Normally when playing, all the LEDs work as they're supposed to when I switch banks and patches.
It's just the calibration routine that only lights up half of the LEDs instead of all of them.
Any ideas? Again, everything works, except that the calibration routine doesn't light all the LEDs, just the 4 upper ones.
Bank LEDs are off as well.
Maybe my 8048 is just tired and can't source that much current at the same time...

The second problem is with the CHD MIDI kit.
I just installed the CHD MIDI retrofit kit on my Polysix.
However, it's not working properly.
I am sure I installed it correctly and I have pushed it down into the keyboard connector all the way (it required a bit of force).
The symptom is that I am getting random keypresses as well as unstable pitch. I can sometimes play on the keyboard but everything gets interrupted by bursts of random keypresses. I see the voice LEDs on KLM-366 light up (usually voices 0-3) at the same time.
I don't know exactly what the CHD kit does but I assume it just hooks onto the keyboard scanning bus and simulates keypresses when it receives MIDI note data. I have emailed CHD about this problem but since it's Easter I expect it'll take a while before I get any reply.
I was looking for a pin without activity when the CHD board was removed and found P15 of the 8049 on KLM-366 was constantly high.
Pressing C3 (or C4, don't remember) seemed to generate a lot of pulses there, I guess as part of the keyboard scanning process. Fine.
When I measured P15 when having the CHD board back I saw some random pulses on P15, without me touching the keyboard...
So, I assume either the CHD board is faulty and generates trash, or the keyboard bus can't handle the extra load of the CHD kit.
The levels seem fine (about 0-4V) so I don't think that's it.
Removing the board and just plugging the keyboard connector directly to CN04 makes it work perfectly again, so I know it works.
Has anybody else had problems like this when installing their CHD kit? :P

Happy Easter :)

BR,
Peter


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