Stage EX weird LED behaviour. What's this about?

[jazzystu]

I am nice to my equipment. It gets very well looked after. It is stored properly, never damp, never has beer tipped in it, never gets dropped. It gets treated like a baby. It most certainly does not get bashed up like a gigging instrument and thrown in vans etc.

I have a Stage EX88 and a while ago, it started "doing this". It plays 100% fine, but there seems to be crosstalk between some leds. These appear to be the uppermost drawbar and the keyboard split points, these link to the piano volume control. Turning the volume control causes the leds to randomly move. This is a concern.

It's about time I uprated to a newer model and at the moment, I can't really do that, if after a while, these things are doing to start breaking down and playing up. I do remember in about 1993 or so, getting rid of my Yamaha P100 Clavinova and getting a Rhodes, because of the unreliability of electronics.

The instrument plays fine, and I've had the top off to look for dust and things that shouldn't be in there and it is 100% fine in appearance. There is NO dust, or moisture, or metal hair, or rust or anything.

I am left with the feeling that it's about to stop working. Now, is there an easy fix, does this happen often, is it anything to worry about, or should I whack it on ebay and get another Rhodes?

If I really look after something, I expect it to last indefinitely.

[Cornopean]

I don't think there's anything random about that. I'm thinking some sort of parasitic behaviour, possibly caused by some bad connection, possibly the earth. I would expect that the affected LEDs had some kind of commonality in their circuits or control chip, or maybe they are matrixed over the same parallel wires and something in the demultiplexing is going slightly awry. I would also expect that this was likely to be an isolated incident, as the LEDs would not normally be connected directly to the DSPs or audio circuitry. Possible cause: weakening of a soldered joint, or possibly isolated part-failure of an LED driver IC or something similar.

Disclaimer - my electronics degree was a very long time ago.

[pablomastodon]

if you expect electronics to last indefinitely, then you should also expect to have your expectations unmet on occasion

solder may look fairly solid, but in reality it is not. There can be degradation over time, oxidation, even slight migration (a la glacier). Somewhat similarly, electronic components can experience failures.

I agree with Cornopean that either weakened solder joint(s) or multiplexer will likely be at the root of this issue. This will seemingly require the attentions of a competent tech

[jazzystu]

Hmm. Nord Stage 3, or Rhodes Suitcase 88 Next....?

[pterm]

I don't have the EX schematics, but I believe the Electro 2 schematics are similar. http://www.workhousepoets.com/NE2%20Ser ... matics.pdf.

These Nords use a matrix-output drive architecture (the complement circuit to the matrix-input used by the keybed). This appears on the schematic sheet marked "nord electro panel board vers 1.00"


The behaviour I see in your video leads me to suspect you have a short-circuit between two pins on the device (U8) driving the bank of transistors (Q1-Q9). --These component designations likely differ on the EX though.

The likeliest explanation is conductive debris between two pins, but also possibly a failed device.

To see if it is debris might be something you want to undertake yourself. --If you want assistance (e.g., to help identify the circuit elements from photos you take), please post or PM me.

[jazzystu]

Thanks. When I am sufficiently bored, I will take it to bits and run my geological lens over it.

[offrhodes]

if you expect electronics to last indefinitely, then you should also expect to have your expectations unmet on occasion

solder may look fairly solid, but in reality it is not. ...

Frankly, for what we pay it is perfectly reasonable to expect that it will last decades.
Solder technology is a standard engineering application. It has gotten a little harder now with ROHS but still there is absolutely no excuse for bad solder quality.

I'm explicitly not stating that Clavia has any such problem, but I wouldn't accept any argument in the direction of "soldering is not permanent".
It is, if done correctly, and "correctly" is standard engineering with established procedures.

[pablomastodon]

Hi Offrhodes,

Philosophically I would like to agree but empirical evidence in the field sometimes differs. Some instruments live out their lives in pristine studio environments with pristine mains power. Others move about the planet and are subjected to suspect mains power, sub-freezing temps in aircraft cargo holds and excessively high temps locked into car trunks or equipment vans, sometimes all on the same day. Exposure to pyrotechnics fallout, cigarette/cigar/other smoke, fog juice, salt air from waterfronts (or on cruise ships). In the real world some things will sometimes fail. Most any experienced tech will be able to relate stories of having "fixed" something by simply reflowing some select solder joints. Prior to my in-depth exposure to the repair side of this business I would totally have agreed with you, but have since seen some evidence to the contrary.

Also, failures are the occurrences which make themselves known. People whose instruments are not failing do not commonly bother to write forum posts to that effect, or send emails to Nord saying so. Incidence of failures is actually extremely low when considered in relation to the total number of instruments out there in use. We all hope and expect to have our instrument purchases last in perfect condition for a very long time. Hidden across the room from my Nord collection is a rack of non-Nord synths. Roland MKS-50 has never been in the shop, nor has Yamaha TX81Z, but Roland MKS-30, 70 and 80 and D-550 have all needed work over time, as have Korg EX-800, EX-8000 and MS-10.