Korg Forums

[maphill]

Hi all,

Looking for some expert assistance. I just sold my OASYS 76, which I was sure was in perfect condition. The purchaser has been checking it out for a few days. He says:

"everything tested well except for the three leftmost knobs in the mixer and modulation section of the control surface. They are the Pan cutoff (#1 from left), the EQ trim resonance (#2 from left) and Low EQ EG intensity (#3 from left) round knobs. Functionally they worked, but the LED lights around each of these knobs did not light at all"

Is there a setting that would explain this? Is this a common failure?

Finally, has anybody paid to have this fixed before?

I really hate shipping claims...

Thanks for your help,
Mark.
_________________
Korg KRONOS 73, Trinity Pro, Monotron,
Roland FA-06 and Fantom 6, Roland TDK-15
Big Knob, Sonar (Previously, OASYS 76)

[Hedegaard]

Was this a personal, pick-up sale as a private person to another private person?

[maphill]

No, it was shipped across the country. So, if I can verify that the problem is indeed a problem, I'll have to make a shipping claim or pay out of pocket.

Do the LEDs on the first 3 knobs light up for you? I had thought mine did, but I just want to verify with someone else.

Mark.
_________________
Korg KRONOS 73, Trinity Pro, Monotron,
Roland FA-06 and Fantom 6, Roland TDK-15
Big Knob, Sonar (Previously, OASYS 76)

[offshoretechman]

Not in front of my 88 O, but from what I remember everything lights up as you change the value of the rotary dials to indicate position. Wondering if something came loose being just the first 3 and possibly could have during shipping. I would imagine they would have split up the power sources to banks of buttons, rotarys, and led's to distribute the 24 volt load and if there are multiple power supplies I would bet this was done. Another problem could be if it's not the power it could be the the signal for position of the knob that comes from the control circuit board for it's indication and would hope it would be a possible loose wire..... and not the board. not sure how technical the buyer is but he can try re-seating all the plugs and ribbon cables inside the oasys if he is willing, look around inside to get familliar with what he has purchased and do any possible dusting and cleaning to prolong the life of his O

http://synth.me/music-gear/inside-korg-oasys-synthesizer-workstation
_________________
Oasys 88 - Roland Super JX-10 - Yamaha DX 7 II FD / Grey Matter - Korg Z1 with 6 voice Z1 expansion board - Korg triton 61 - Protools 8 running on Snow Leopard

[Akos Janca]

[attitudeadjust]

I had a recent situation in which the screen representation of the sliders behaved erratically every now and then. This started after I moved my Oasys to a gig and back. Talk about panic mode.

Anyway I opened up the panel and slightly pressed all of the bundled connections into their respective circuit boards. Restarted and everything seems to be working fine.

Might give this a try

Spencer

[maphill]

Thanks for the input.

The purchaser went in an checked the connections. He said it all looked good... and the knobs are working, just not the LEDs.

Does anyone have the part number for the knob assembly (including LEDs)?

Mark.
_________________
Korg KRONOS 73, Trinity Pro, Monotron,
Roland FA-06 and Fantom 6, Roland TDK-15
Big Knob, Sonar (Previously, OASYS 76)

[Akos Janca]

[maphill]

Thanks for that link, though I'm having trouble deciphering (and I'm an EE!).

Does any body have technical diagrams from the service manuals that can tell me which part would correspond to the 1st 3 knobs and their LEDs? (on an OASYS 76).

Are they LEDs, or Photo couplers, or Knobs or Control Knob or...

I called PartsIsParts but they didn't return my call.

Thanks,
Mark.
_________________
Korg KRONOS 73, Trinity Pro, Monotron,
Roland FA-06 and Fantom 6, Roland TDK-15
Big Knob, Sonar (Previously, OASYS 76)

[offshoretechman]

I inquired to Korg about where to purchase the service manual for the Oasys about a week ago........awaiting reply
I see someone has it on Ebay but it's a photo copy and would rather purchase the original
_________________
Oasys 88 - Roland Super JX-10 - Yamaha DX 7 II FD / Grey Matter - Korg Z1 with 6 voice Z1 expansion board - Korg triton 61 - Protools 8 running on Snow Leopard

[rudolfck]

There are 11 led's both under the knobs, sliders and
master. If none of them work, i.e. all out, it is not the led's
but the boards they are on or connections.
There are 8 knobs. Looking at the diagrams I figured
you get all
8 circuits as part code: 500362009007,
part name: VR RK11K11409A9L with the note KLM 2419
(which just indicates left panel on the Oasys), quantity 8.
Appears no difference between 88 and 76 in this case.
I am afraid I only have a printed copy of the diagrams etc.,
I think I received that from a member of this forum but I lost the pdf file.
Hope this helps.

Rudolf
_________________
rudolf
Oasys 88 VS2480 MPC4000 Rhodes88 Hohner
Clavinet, etc.

[maphill]

Thanks for the info Rudolf.

My hardware friend has this analysis based on the service manuals:

-----------

So board KLM-2421 is the module that has the LEDs on it. They are illuminated using a scanned matrix, which isn't a surprise. Since all LEDs for the three knobs are out, we know that it's the columns (as drawn on page 11) that are missing from the scan.

These three signals, LS[08:10] are routed to a connector and out to module KLM-2418, which shows up on sheet 8. The signals find their way up to three drive transistors Q1, Q2, and Q4, which are being driven by IC2 in the top-left corner of sheet 8. This IC is an octal flip-flop being used as a latch. Signals for it are being provided by the system data bus, which is 16-bits wide.

I'll stop there because the problem has to lie someplace in that description. Why? The system is operational, which means that the base data bus *must* be working.

So here's a few scenarios:
1) IC2 has failed. I wouldn't consider this peculiar, except that only 3 of its 8 bits will have failed. Not common, but possible.
2) The three drive transistors all failed... simultaneously... Not as likely given the three are essentially isolated. A surge in a power signal that could take out these three would have taken out others as well.
3) The connection between the two modules is faulty. This is actually the most probable. Connectors can be flaky, especially ribbon connectors.
4) There is a newly-introduced mechanical defect in module KLM-2421 which has severed the three drive signals for those LED's. In other words, the board has a crack in it, and that crack broke the three signals. Given the way those knobs are in the top-left corner and sticking up, this is also highly probable. Drop the thing wrong and /snap/.
5) All 30 of those LEDs simultaneously blew. Included for completness' sake (as well as humor).

I don't think the 74HC4051's on sheet 9 are to blame. They're not even on the pertinent side of the drive chain. We'd look there if, say, the 4th LED of every knob was burned out.

It's really too bad that I can't get my hands on that keyboard for you. I could probably give you the definitive answer in less than 15 minutes. Since I can't, I'd hedge my bets on the KLM-2421, but only if you're certain the cable between 2421 and 2418 has been checked.

----------
I gave some misinformation in my last email. Those 74HC4051's on page 9 aren't in the drive system for the knob LEDs at all. They couldn't have anything to do with this.

And there's 33 of them, not 30.
------------------

So, I'm hoping that the buyer can reseat the relevant ribbons and that will fix it. Or I'll try KLM-2421.

We'll see,
Mark.
_________________
Korg KRONOS 73, Trinity Pro, Monotron,
Roland FA-06 and Fantom 6, Roland TDK-15
Big Knob, Sonar (Previously, OASYS 76)

[Hedegaard]

And about time too, this has been dragging on forever
_________________
.....Still waiting for the allusive, missing EXf for Oasys.....

[maphill]

Agreed. My buyer doesn't check email very often. It won't surprise me if this takes another 2 or 3 weeks.

Oh well. Something to do till the Kronos arrives.

Mark.
_________________
Korg KRONOS 73, Trinity Pro, Monotron,
Roland FA-06 and Fantom 6, Roland TDK-15
Big Knob, Sonar (Previously, OASYS 76)