Nord User Forum

[petersturton]

Good evening. This is my first post. I got a second hand electro 2 6 months ago. All well until today when I turned it on. There are now 7 buttons that don't work. They are the two navigator buttons to the left of the display, programme buttons 1 and 2, and the upper drawbar buttons for the 16', 2 2/3' and 1' sounds. All other buttons and pots work fine. I can still get all the sounds if I work around the button problem, but I am now limited to 6 pre-sets. I have tested the prongs that come out of the buttons and they are all making the proper connection when tested with a circuit tester. I have disconnected and cleaned the ribbon connectors. Is there a common circuit that links these buttons? Any ideas where to start looking for the fault? Thanks for any advice. Pete

[pterm]

Hi Pete and welcome to the forum!
The Electro2 schematics and service manual exist online. These are the only Nord schematics publicly available:
http://www.workhousepoets.com/NE2%20Service%20Manual%20&%20Schematics.pdf

Since you own a circuit tester I assume you understand some electronics, so this ought to help you. See sheet 7 "nord electro panel board".

The nord uses a matrix key scan, so this is not easily diagnosed without only a multimeter.

Before touching any electronics be sure to touch your hand to a larger metal surface (like the nord chassis) first to discharge any static electricity.

Check the connectivity first between the U1 device and all the switches that share a common signal line.
Check for open circuit or short circuits to ground or adjacent pins on the U1
Check the pull up resistor on the common line (value and connectivity).
Check the diodes for correct diode behaviour. Compare resistance, voltage drop across the diode to other diodes on working circuits.

If you need help with understanding the electronics or test methodology please send me a private message (see the "UCP" menu at the upper right of the forum webpage below the forum's search bar).
Cheers,
-pterm

[petersturton]

Thanks to pterm for advice. I have checked the schematic. The seven buttons that don't work are all on the same common line, right at the top of the diagram. They are all continuous with leg B1 of the chip labelled U1 on the schematic. Resistor R34 is showing the correct value. Diodes running from the switches show same values as other diodes in unaffected lines. Looks like it may be a chip fault? I can find a replacement here...https://www.farnell.com/datasheets/1878566.pdf
Anyone had experience of this fault and/or replacing the chip?

[cgrafx]

seeing that the part is a surface mount chip, its much more likely that the chip is fine, it just has a cracked solder connection.
You really can't do a proper test of the circuit with a multi-meter. You need an oscilloscope to actually watch the circuit in operation and see if the line in question is actually scanning.

However, based on your current state of investigation, the most likely fault is a broken solder connection, not a faulty chip.

Resoldering the pin is fairly straight forward, but can result in shorted pins if not done properly.

I suggest you spend some time on youtube researching the process of re-soldering surface mount devices. If re-soldering the pin(s) doesn't work than you can proceed with removing and replacing the chip, but to be honest, if you don't have the proper equipment and experience to do this type of surface mount rework you can just as easily destroy the circuit board which will become an infinitely more expensive repair. (its very easy to lift traces off a board, particularly when you have to heat up all the pins at the same to remove the chip. This is usually done with a specialized heat gun.

Personally, I might take a stab at re-soldering the pin, but beyond that I'd send the keyboard to a qualified repair shop.

[petersturton]

Ok thanks. I have a fine soldering iron. Wish me luck.

[petersturton]

Progress report. I cleared some space around the chip by removing three plastic LED light clips and the switch directly below the chip...to allow easier access for my soldering iron. In removing the switch I stripped off the trace and overheated one of the pins in the switch causing it to move, press on the copper spring contact, and create an always-on switch. This was cured by heating the switch pin and pressing it from the inside to force it back to its original position. Much swearing later I applied flux and a gentle touch with the soldering iron to the suspect chip leg and it looks like I have a good solder connection on that leg. However the original fault is not cured. Now to find a local micro-soldering shop to try a replacement chip. Chip costs a few pounds, soldering likely to be tens of pounds.

[Mr_-G-]

Progress report. I got replacement chips. Had to order a minimum of 5, even though I only needed one. Chip micro-soldered by a tech and now keyboard works as it should. Chips cost less than 50 pence each, packaging and postage cost £13. I now have 3 spare chips. Anyone need one?

[JayDee]

Well done Peter. Glad you solved the problem. Hope I won't ever need a replacement chip.

[pterm]

Very good news! Thanks for posting your outcome.