Korg NS5R ai2 Synthesis Module (1996)

Half rack Unit from rompler era, derived from N5 keyboard, I made a page some time ago with some specs, you can read it here.
Quick info: a very 90 style, pretty large 144 pixels x 44 (with variable color) with fun icons representing different functions and parameters. Nine keys for accessing the functions, as well as a rotary encoder and a handy sound preview button. Waveblaster daughterboard wavetable can be installed inside as expansion, but pay attention to drawing.

The modules arrived

Another nice buy on "Craig": a combo of two half-racks: a Kawai PHM pop (or something, based on more famous K1) and the more interesting of the bunch: a Korg NS5r which I used to have some time ago. The seller posted some pictures of the display switched on and certified it was perfectly in order and good sounding. 

The package arrived, but Marcel the cat did not agree to let me play it for the moment.  I will try it later.

What's wrong with it?

The module is indeed in good shape. I did not remember the PSU was internal with 2 prongs Philips, I was expecting a classic 9VDC.

So, let's start it pushing the button... and... nothing on display :(  no light on panel. The current was flowing indeed and a hum sound can be hear from the audio out. What the hell happened? Before making a voodoo doll of the seller, let' open it.

UPPER Soooo 4 screws on each sides, plus it is necessary to remove all screws on the read (pay attention to different sizes) and the nut around the data encoder. Just don't touch the screws around the transformer unless you need to remove it for some reasons or better access to the mainboard (which is a tricky). Then 6 flat screws around the front panel. Remove the flat with red wires to going from main board to display.  An earth wire is connected from main board to display, remove the screw, I pulled before removing it breaking the solder. PAY ATTENTION to EARTH wire!

UPPER  - Checking the fuses I noticed you can actually change the machine to both 110V or 220V changing the connector (AND CHANGING THE FUSES ! don't do this if you don't know what you're doing!) The board is pretty good shape at first glance. 

UPPER a LOT of SMD capacitors there, but nothing in bad shape, all clean no leaking no shorts. The ESR was not fantastic but ok. That was my first fear, but I don't think this should block the whole machine. Note the DAC Burr Brown PCM1717 on IC6.

Voltages rails

The only service manual available is not really friendly and not so detailed (you can find it at the end of this page). 
There are 3 mains rails called "A-B-C" in respective order: A +5V, B + 12V and C -12V.  
Both +-12 voltages were there on 7812 and 7912. A bit more complex the chopper regulator PQ1CG1 with following PIN: 1 Vin, 2 COM, 3 Vout and 4 Adjust. The last regulator was ok, but measuring a random memory chip the +5V rail is simply missing. A good news.

UPPER: checked D10, all resistance, C100,  C108, C114 no short and good ESR (way better than SMD!) , but no voltage on them: the problem should be around this block. I noticed the resin glue between nearby electrolytics and  L42 was loose and the inductor was a kind of wiggling. Voltage is OK from PQ1CG1 to L42 input, but NO VOLTAGE on OUTPUT! 

UPPER and BINGO! one of the pins was brokend and making no contact!  I wonder what happened? maybe it broke during the shipment? maybe the resin glue did not blocked the inductor? note that also the two inductors near the primary prongs are wiggling a lot and glue just dried. Anyway I managed to solder a new pin to it, not much left, but enough to fit in. A quick soldering and now testing. It should go now.

Reassembling and testing

How nice! it just started! sound is good, I will just have to check capacitors on the future. 

If you need it, here's the english user manual and here the SERVICE MANUAL (also for DDM110)


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