Sean's blog

LEGO Mindstorms RCX cable rot / decay

Some of the LEGO I have in the house must be 30 years old. It’s as good as the day it was first unwrapped. I have to admit to being disappointed when one of my two RCXes stopped responding to the IR tower. I was pleased the other one was still working just fine and was looking forward to testing my old research software (a program that uses a ‘genetic’ algorithm to create a novel kind of controller which I then simulate on the RCX). When I looked through the bag of cables I discovered a catastrophe – the cable sheaths had rotted away:

LEGO RCX cable rot / decay

It looks to me like some kind of mildew and varies in severity from cable to cable, but I don’t have a single unaffected piece. The best ones (click on the photo for a larger image, see the top cable) have just a little cracking around the entry into the terminal brick. The cables sheaths on these ones are unusually soft and the black sheath surface can be easily scraped off with a thumbnail, though not down to bare wire. Most of the others have far worse decay where the sheath has disintegrated into flakes or lumps which has fallen away leaving bare wire.

I rather stupidly opened the worst-affected piece – a light sensor – to see how difficult it would be to replace the entire cable, but broke the light sensor, probably while trying to de-solder the glued-in end of the wires from the small PCB inside. I think my best bet for now is to clean the bare cables, cut the cables quite close to the terminal bricks and insert new wires with boots over the joins. I can’t buy any replacements at the moment as I’m due to move from Malaysia to the UK in the next few weeks. I may well check eBaY for RCX cables when I’m unpacked in the UK.

I’m a bit rattled by the severity and extent of the failure of these cables – LEGO should last forever, right?

Update: Not sure why I forgot to update this article, but I filled in a ‘contact us’ form at LEGO’s website soon after writing this article and LEGO sent me some replacement cables within days of the article’s date. Thanks to Juan Carlos for reminding me with his comment, I can finish the article with thanks also to LEGO!