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Concert C-46

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Joined: 22 Apr 2014
Posts: 2
Location: Washington State

PostPosted: Tue Apr 22, 2014 8:58 pm    Post subject: Concert C-46 Reply with quote

Recently purchased a Korg Concert C-46 series online from www. shopgoodwill.com. I made the mistake of not asking whether the unit works. The listing says it "powers on". Yes, when you "power on" the unit, LED's do light up and also when you make different selections and the appropiate LED will light when selecting that voice or whatever. Anyway, there is no sound coming out of the speakers or the headphone jack. Began troubleshooting the circuit boards and found the main board KLM-1653 has been worked on in the past. Several screws missing, terrible solder connections, a burned out trace replaced with a jumper with again lousy soldering jobs. Also found a couple of cold solder joints. Cleaned up soldering joints but still other problems exist that I cannot physically see even with a magnifying glass.

I've searched the internet for companies that might carry replacement circuit boards and so far to no avail. I was also hoping to find "parts only" Korg pianos...My question is...does anyone know or have additional information on how I can find a replacement board for my piano? Thank you!
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Joined: 08 Mar 2015
Posts: 1

PostPosted: Mon Mar 09, 2015 12:53 am    Post subject: Also need repairs Reply with quote

Hi. Sorry, no info as yet on parts/boards. I'm also looking for parts.

I came by my used C-46 via a friend about 2 years ago. He had already had it repaired once but told me it had given him no trouble for at least a year after that. He offered it to me at a 'too good to pass up' price - he already has six other keyboards and needed to make room in his home studio. My middle-schooler was just coincidentally interested in learning Piano, so this seemed like a pretty low-risk way to get a (really very) nice unit for probably a 10th (or less) of what it cost new and get my son started.

We had about 18 months of trouble-free operation from it. Then, the amplified sound, gradually began to simply fade to lower and lower volume levels. We realized why: the entire right channel had gone out. Even so, the unit was still quite usable (loud enough) with the left channel while my son did his first year of lessons. But in the last six months, the left channel too fizzled out gradually and was unable to amplify the keyboard. There is also NO output on either the headphone jack, nor the RCA (line) output. Most curious, is that I can run a signal into the (line) _inputs_ and I get sound just fine on the LEFT output. The right channel is definitely out - all I can hear through the speaker is very low-volume fizzing/crackling. If we have the volume at 100%, and the room is quiet, we can just barely hear tones from the left side speaker, but as a learning instrument, it's now unusable.

This past week I opened it up and dusted and cleaned everything thoroughly, pulled, cleaned (with contact spray) _all_ of the connectors in the unit hoping maybe it was just a bad connection somewhere. No luck.

So I have two issues:

1. The _right_ channel main amplifier is definitely not working at all. I can see the heat transfer grease on the main output Transistors (MOSFETS?) has (my guess) almost definitely been redone - smeared all about the heatsink in that area - not neat and clean like (what is probably) the intact left side from the original manufacturing build.

2. There is no keyboard output feeding the poweramp section, so there's a bad op-amp or pre-amp gain stage somewhere that's suspect.

So my unit definitely likely needs either outright board replacement or hours of technician-level troubleshooting and subsequent bench work.

I checked on ebay and around the web this morning - parts for these units (and even used C-46s themselves) seem non-existent. I really like this unit, but by the time I track down either parts or a repair person and let them dig into it, I could probably just pick up something like a Yamaha P-35 for $300-400 and get on with things.

Still, I hate to give up on this unit - this Concert (C26/36/46/56) series are really very nice sounding units. The internal construction does seem rather decent, not too bad imo, and I can see care was taken with the cable routing, etc. - manufacturing touches typically not done on more cheaply made units. I see a mix of midrange quality components (not all the caps are electrolytics, plenty of polystyrene and mylars) and the circuit cards don't seem 'packed' (decent layout/design) and most of the solder joints I've looked at seem well done and clean. No remnant flux anywhere - a good sign in my experience. Also, this is a weighted key unit, so tossing this out seems like a tremendous waste. I'm guessing the keyboard sub-assembly alone has got to be worth at least $200 as a replacement part. I can't believe folks are/were just trashing these units at the first sign of trouble.

Further, I deeply despise obsolescence design manufacturing & thinking and think there's no way a unit built this good should not give at least 30 years of service. I have Pioneer, Sansui & AKAI receivers and tape decks from the mid 70s which are still going strong, with not much more than a yearly dusting.

I'll also be searching for parts and/or repair information this spring and will update this thread with anything I learn.

Sorry for the long post.
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Joined: 22 Apr 2014
Posts: 2
Location: Washington State

PostPosted: Sun Jul 19, 2015 2:27 am    Post subject: Korg Concert C-46 Reply with quote

I have searched high and low for a replacement circuit board (KLM-1653) or an "as is" condition Korg digital piano. I've been off and on looking on the internet on all websites, ie, eBay, craiglist.org and other electronic media, thrift shops, pawn shops, garage sales, swap meets, etc. And so far, to no avail! I did see a listing on eBay a while back for a Korg Concert C-46. It was a "local pickup only" and was somewhere on the east coast. I live in WA state and the expense would not have made the deal worthwhile.

It will be a matter of "luck" to find a such a Korg Concert C-46 in "as is" condition for the right price. As long as the audio/power amp circuit board is still operational, it would make no difference if the piano had other electrical or physical defects.

I'll just keep on searching and surfing the web. I'm retired so I've got ALL THE TIME IN THE WORLD! LOL!
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