Monopoly VCO-4 prtamento/detuning issue
This is my first post here. It seems a great yahoo Forum with knowledge base and I would like to thank all people here for sharing their help to others. That's really very rare to be found at that days.
Recently I bought a 2nd hand Monopoly, which had some issues.
I cleaned some key contacts which they were filthy and were not working during pressure and I also cleaned some pots internally with the appropriate alcohol which were not accurate and everything seems work fine except one thing:
1. Portamento Knob is at 0
2. VCO1, VCO2 and VC03 are almost tuned correctly
In mono or poly mode:
VCO4 comes "the portamenting way" from some note (not sure which) to almost 4 notes out of tune from the other VCOs.
For instance if I play a C, all other VCOs plays C, VCO4 comes with a portamento sound from some other note.. and stops tuned to F. When it stops to F, it can be detuned from it's know but it can only come one tone up or down, it cannot come to C.
Is this the same issue like http://launch.groups.yahoo.com/group/korg_mono-poly/message/598 ? or it is another issue ?
I opened the case, I noticed that I do not have the version of Monopoly which pictured here: http://fa.utfs.org/diy/korg_monopoly/monopoly_VCO_pcb.jpg in order to adjust the VC4.
I have this version: http://tinypic.com/r/141p7di/5 (you can use this photo in any site for repair info if needed), so I assume that the pcb KLM-354 is between the board and the front panel of Monopoly, correct ?
Could you help me if I need first to replace the possible defective HD14066BP or one relative (if this is the cause of the Portamento bug on VCO-4) and then to tune the VCO4 or I have to check/replace something else ?
The instrument had been repaired on 9/2007 but I am not aware what issue had then or if it was a proactive maintenance or any other issue.
Thank you very much for reading my issue
No problem Florian, you already did a lot to help me find what causes the issue. It seems that I have to give it for service in order to be checked further. Portamento potentiometer seems to work fine.
Maybe a TL chip is defective or something goes wrong to line from this pot to VCO4.
I will give it for service next weeks and I will let you know when I have the results.
Thank you very much
--- In email@example.com, Florian Anwander <fanwander@...> wrote:
> > All four measures seem to be the same:
> Hmm. Now I have no further idea where to look for. Sorry.