Korg DTR-2000

[San]

Hi all,

Hopefully someone can advise me what to do next trying to repair my Korg DTR-2000 rack tuner.
Everything seems to look and work fine but it's not tuning...
I allready did some trouble shooting:

In the test mode all LED's are working fine and also all push buttons do their jobs.
The mute, input select, Chromatic, mode, flat etc,etc push buttons are switching properly
The sound function, to hear the notes you want to tune, is audible through the sound output.
So far so good....

When hooking up a test generator with 110 Hz / 150mV to input 1 or 2, I can measure the same values when measuring the output jack, even when the tuner is not powered.
On the klm-2358 PCB I measured this signal on pin 20 (input) of IC M8303 (IC1).
On this IC the 5 V supply is availabe on pin 57 (Vcc) and pin 19 (reset)
All plugs, wiring, elco's and connections looks fine.

But in Cent, Strobe and Hz position nothing is moving...

So if there's anyone who can help me it would be very nice.

The service manual incluing schematics:
https://www.manualslib.com/manual/10...-Dtr-1000.html

Regards,

San

[Jazz P Bass]

Not too sure, but do you have the full 9Vdc supply?

The meter display is all controlled from a microcontroller.
If you have the correct 'select' inputs and the unit is not functioning correctly, that pretty much points to the micro. (IC 1)

I would check IC 2, reset IC for function.
Does the output pin which goes to IC 1/ pin 9, go low briefly at start up?

[San]

On IC2 I measure approx. 5V on pin 1(supply) and also 5V on pin 3 (output)
As I undertand from the M51951 data sheet the output should have a 200 micro second delay to reset IC1.
I just unpacked a new Keysight DSOX1102G oscilloscope.
I can hook up the probe CH1 to IC2 pin 1 and probe CH2 to pin 3, I can see both voltages but I have to find out now how to capture the startup signal....

[San]

It seems that there's not a delayed output signal on IC2.
I'm looking for a replacement IC but it's not so easy to find a M51951AML sot-89.
Does somebody knows where to order it? I have checked Mouser, Farnell, etc.

[g1]

Maybe this one from wellgain electronics, but the price seems ridiculous. Have you checked with Korg?
https://wellgainelectronics.com/volt...m51951aml.html

[San]

Thanks g1, it is ridiculous, that's for sure, but I didn't check with Korg yet.

[nosaj]

It seems that there's not a delayed output signal on IC2.
I'm looking for a replacement IC but it's not so easy to find a M51951AML sot-89.
Does somebody knows where to order it? I have checked Mouser, Farnell, etc.

Sometimes when you can't find what your looking for there . a phone call to customer service will help .Sometimes.

nosaj

[muzzy]

Hi!
I was searching for some info regarding repairing Korg DTR tuners and found your post. Were you able to make any progress on fixing your DTR 2000? I have the same problem with my DTR 1000 - audio signal is present on the input pin of microcontroller but tuner isn't tuning. I thought that maybe this pin got damaged internally. Unfortunately I wasn't able to buy this microcontroller to replace it (I asked KORG and some local distributors - they said it was discontinued).
Either way, I was curious if you managed to do something with this tuner or threw it out as a lost cause.
Regards,
m.