Hello all, this is my first post to the EB forums! I've recently unearthed my childhood collection of Lego and am doing a little refurbishment on my 6990 Monorail Transport System. Since I was pretty OCD about my sets at that age, and since my parents packed things away pretty attentively during my Dark Ages, the set is in outstanding condition. I thought I'd share some of the experiences I've had, and some questions that arose, as I've been rehabilitating it.
There was only one missing piece in the set, a simple white 1x2 plate, so no problem replacing that. Also, the set has only 7 of the large supports, enough to build the main model—but the online inventories say there should be one extra, for a total of 8. I don't recall there ever being an extra; was this included in later editions of the set? Right now I am considering the set complete with 7.
In building the set, I broke one of the white antennas because of the very tight fit of the trans-red dish onto it. Again, this was easy to replace (I got two in case the other one ever breaks.)
Other than the 8th support, I have all the various extra parts that came with the set: the different 1x1-size parts, trans-blue minifig visor, trans-red light cover, etc. I even have an extra white 1x4 brick for some reason. Was this a genuine extra part, a factory packing error, or did it just get mixed into my set by mistake?
My biggest challenge is with the electric connector wire. This set came with the rare plate-sized connector, which has small clips on the underside of its plate ends that cover the electrical solder as well as providing the clutch power for the bottom. The tab that holds this clip onto the plate itself is very tiny, and with age the plastic seems to degrade so that these tabs break off and the clip becomes loose. It will often be pulled off by the act of disconnecting this part from the battery box studs. (The same degradation results in tiny cracks forming in the plate ends, which must be why so many of these listed for sale have corners or edges missing. My part has the beginnings of these cracks, but so far the damage is minimal.) This photo shows the underside of the part, both with and without this clip:
I am currently sourcing replacements for this, but there are very view for sale and most of those seem to be in worse condition than my own. I'm wondering if I'm better off just gluing the clip back in with a plastic cement; has anyone else ever dealt much with these vintage pieces?
As you'd expect, many of the white and grey parts in this set had yellowed, but I've had good luck reversing this. After reading about numerous un-yellowing methods of varying complexity, I'm glad to say I've had good success with a simple 3% peroxide solution in direct sunlight—no added OxyClean or higher strength peroxide solution—and most parts have returned to white in a few hours. I'm using clear plastic containers, and I'm sure it helps that I have a white table outside to put them on. I made a quick cornstarch & peroxide paste for the battery box, since it can't be submerged, and the large baseplate, which is too big to dip.
A few parts showed more resistance to de-yellowing: the webbed radar dishes needed some extra time, and for some reason the 1x1 cones as well. The soft plastic of the flexible hoses did not respond to the treatment, but the end pieces did, so these are now a two-toned affair. I'm currently re-dipping the long Technic rack pieces; these almost look like they turned more yellow. Are they a different plastic, and should I be using a different technique for these?
Meanwhile, a couple of parts (the rack winder and the motor housing) never yellowed and are still completely bright white—they must also be a different plastic—and so I'm using them as my color comparison to the treated parts.
EDIT: One of the straight track pieces, which was significantly more yellowed than the rest of the track, ended up suffering some fading and is now a bit of a chalky white on the top and one side. I knew this was a possibility with light grey parts, but even though I was getting the yellow out within a few hours of treatment, I somehow assumed that the bleaching problem wouldn't happen that quickly. Of course, it had to be the relatively rare (and thus expensive) straight track, so it will cost I bit if I decide to replace this part. :-(
As far as I can tell, I have the complete packaging save for the original polybags. I have the outer box top and bottom, red inner box, four plastic inlays and a plastic inlay lid. I even have the cardboard space backdrop and the original catalog that came with the set. The instructions are in excellent shape, too: only the outer leaf (cover and fold-out back page) has separated at the staples, but the booklet itself is otherwise undamaged.
Of course I checked the electrical function and everything works perfectly—although I went through three 9v batteries that I had in my drawer before realizing that every one of them was dead; it wasn't the monorail! A trip to the store and one new battery later, all was well.
I have not yet decided if I will try to sell this set or keep it in my collection. I believe I can get quite a good price for it as the condition is excellent and the set is 100+% complete. Then again, I might hang on a bit and see if the price goes up a bit over time. :-)
Thanks for reading, and I'd love to hear about others' experience restoring this set or with some of the issues I've found. Meanwhile, my next project will probably be the 6285 Black Seas Barracuda, arr!