Disassembly issue of big metal 100CPR CNC type encoder - Page 1
Forum section: electronics / repair

author: electr_peter
author_rank: Unknown
timestamp: December 14, 2015, 09:20:34 pm
content: I have bought damaged encoder - it draws much more current (3-4 times more) at rated voltage and gets slightly warm. Issue between me(buyer) and seller is resolved.I have used such items before without a problem. Circuitry inside can not be that complicated, so I should be able to repair it.The main question is - how to disassemble such encoder without destroying it in the process? I have never seen insides of such encoders and all my disassembly attempts failed so far.First I checked stationary parts - no luck here. Screws on the bottom are firmly placed in metal ring, nuts only hold rubber gasket.This metal ring is firmly connected to plastic bottom.I can see green PCB material near contacts through slim gaps.Now onto rotating part - slight pulling produces nothing. Screw seems to only hold the handle in metal top.The only possibility I see is that rotating part is probably made from two pieces - larger ring with numbers and smaller part pressed on the top. However, I still not sure how to take them apart.Encoder in question is practically identical to this one in pictures below.Pictures are taken from this sitehttp://www.buyincoins.com/item/49120.htmlAny ideas how to proceed?

author: electr_peter
author_rank: Unknown
timestamp: December 16, 2015, 08:16:10 pm
content: I will try look closer at the clearances and construction this weekend. Maybe somebody could share high energy X-ray imager?

author: rich
author_rank: Frequent Contributor
timestamp: December 17, 2015, 02:37:29 am
content: Instinct says go in from the top. Maybe remove handle and then pry grey plate up with tool warm air if it is glued?

author: electr_peter
author_rank: Unknown
timestamp: December 20, 2015, 11:00:44 pm
content: I have looked at the encoder with more detail and managed to do partial disassembly.Small rotating handle can be removed from front face. You can see stationary black piece (connected to the body) when looking though this screw hole.Rubber gasket is easily removable from backside. After removing 6 contact terminal screws I could see rotating plastic piece, which was connected to turning handle.Plastic cap on backside is easily removable as well. It hides PCB with contacts and LEDs with photo transistors on the other side. Transistors and LEDs can be partially be viewed from cut-out in the encoder's backside (although it may not very clear from pictures).This encoder is optical type with mechanical indents. Optical wheel is made of black plastic and is directly connected to rotating knob on the front. Photo-transistors and LEDs are mounted on both sides of encoder wheel at specific distances making it difficult to completely disassemble this unit.Principle of operation and schematic of this encoder is trivial at this point. However, I do not know exact specs and part numbers of LEDs and photo-transistors. Also, optical alignment issue and soldered pieces severely limits further disassembly.My guess is that this encoder suffered from slight overvoltage or reverse voltage applied to its inputs, thus damaging transistors or LEDS, which contributed to abnormal current consumption. Or maybe transistors were faulty from the very beginning.I would gladly sell this item for a small price to forum members (for mechanical parts or potential repair). Send PM if interested.