Helpful advice for others attempting to replace a bad rotary encoder in their Rigol DS4000 series:
I also had trouble with rotary encoders on my Rigol DS4000 series scope and since it was out of warranty, made my own repair.
I had a rotary encoder w/push button that began to fail within six months before the end of my three-year warranty. I couldn't do without the scope on my workbench for a week or two, so I decided that when the control became really unusable, I would fix it myself. After all, I been designing circuits and building electronic devices for years and I know enough how to repair these things.
Some time after my warranty expired I contacted Rigol Tech support about purchasing a replacement rotary encoder from them and they told me they are not in the business of selling parts and they said to get it repaired I must ship it to them and they quoted me a repair price of close to 50% of the original scope purchase price, not incl. the high cost of insurance and shipping, just to replace an approx. $4 USD part.
(1) Bourns makes an exact fit replacement part PEC11R-4215F-S0012 (12 detents/rev)
This one has a push-button sw. and detents. Available from Mouser, inexpensive and in stock. It is hard to find a 15-mm shaft length like the original at other major part houses not stocking Bourns parts. Alps doesn't make one that fits.
(2)There is a small satellite control board(Clear Auto Single Trace..etc) delicately attached to the top right corner of the control panel PCB. It is connected to the control panel with a very delicate and much too short plastic flex ulta-flat cable that is so easily damaged, as I have proven to myself. With just a few movements this cable end soldered on the satellite board sheared off like it was cut with a razor and I had to really search around eventually found a used and much wider flex flat cable to effect a repair. I had then to trim it with a scissors, slightly strip the cut end with emery cloth, then solder it in. Finally, a bit of hot glue applied on the flat cable near the soldering point was needed to ensure the cable was was fixed in place and could not move about to shear itself again.
(3)Rigol has slopped on acrylic caulk-like hard white robot snot all over delicate ultra-low profile flat cable connector sockets and it is impossible to repair the scope without first disconnecting the flat cable interconnects to allow access to the underside of the control panel board to unsolder parts. It take some care and time-consuming scraping with a razor/flat screwdriver tip to remove this stubborn gook without damaging these delicate connectors.
(4)As already mentioned by Paul, Rigol has had the bad sense to fasten the front panel with three small screw hidden beneath the front panel decal and this means the decal must be very carefully unstuck from the front panel metal without creasing it or damaging it. IMHO three hidden screws are not really needed, but like the single hidden screw on the back cover under the Safety Conformance label. these screws might have been added just to discourage people from servicing their own equipment. Repeatedly removing this decal will eventually mean it will not re-stick and the scope then becomes techno-junk when looking at the cost of having Rigol replace the sticker front panel. The problem is, from what I've read about may people having trouble with their Rigol scope's rotary encoders, they seem to fail often and some time in the future I will have to replace another on my scope.
Don't get me wrong. I still am quite satisfied with the quality and performance of this scope when I justly compare it to the much higher priced scopes from Agilent or Tek. I just wish it was more reliable and easier to repair. I have a Tek 475 scope that's old enough to have grandchildren and all it still works perfectly and was easy to repair when once it did go sour.