sunnuntai 19. huhtikuuta 2015

Korg MonoPoly

I have a slightly modified MonoPoly. One day it gave out smoke and I thought it was the end of it. First I was not sure what went broken. I decided to change the power supply which normally is a good candidate for problems. I replaced the internal KLM-376 power supply to external +-15V power supply HBB15-1.5-A+G. In place of KLM-376 board there is only left a proto-board with connectors to other boards and a LM7805 +5V regulator. When I first powered it after this repair I noticed that the smoke was coming from KLM-398 board where one trimmer resistor created a short circuit. I changed all the trimmers in KLM-398 board and after that everything was ok. After adjustment procedure MonoPoly has worked normally. I made the modification to KLM-356 CPU-board where you cut the jumper J1. This disables the key-assign-mode reset (changes to unisono-mode) that normally happens when you switch to effects-mode (crossmodulation and sync effect). This mod is explained here What a nice synthesizer !

External HBB15 power supply in a case

The new blue trimmers are top left in this picture

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