Amcor TC-120 Dehumidifier - Page 1
Forum section: electronics / repair

author: Richard_L
author_rank: Contributor
timestamp: January 29, 2017, 04:06:54 pm
content: I was given two Amcor TC-120 Dehumidifiers a while ago by a neighbour who was moving house. One was full of grass seed and the other was covered in oil but they cleaned up nicely and worked well for about 6 months. Now both appear to have developed a fault.When turned on, they emit an audible CLICK and then visibly SHUDDER. This click-shudder sequence then repeats. The one I've used most does this about 150 times a minute to start with. The lesser used one only around 60 times a minute. I've stopped using them because of this problem but if I do leave them on long enough, the click-shudder behaviour slows and stops. Achieving normal operation might take anywhere from 2 to 15 minutes.While the click-shudder is at its most intense, the dehumidifier draws up to 700W (measured with a plug-in power meter). The information placard on the back of the machine states power and current (at 240V) is 230W and 1.3A. After the click-shudder stops, power draw reduces to 18W and it appears to be working normally judging by the frost building up on the refrigeration coils.I have no previous experience with dehumidifiers. Does anyone recognise this behaviour as a particular dehumidifer failure mode? Googling brings up very little of use about this model. About the only useful thing I've found is herehttp://www.fixya.com/support/t15686809-amcor_dehumidifer_tc120_circuit_boardwith the relevant bit beingQuoteDoes anyone have any advice or insight before I start trying to disassemble it?thanks,Richard

author: Seekonk
author_rank: Super Contributor
timestamp: January 29, 2017, 05:17:53 pm
content: A new 78p153sp would give you a Snowballs chance in a cat scanner. It would have to be programmed. A shorted resistor is a new one on me, never seen one. A bad power supply cap could could be causing the micro to reset and keep restarting the motor. That 700W is actually pretty light for this kind of motor start. Not much you can believe from those killawatties. You could buy a rudimentary temp controller on ebay for less than $4 that could do what you say you want. I don't doubt that the existing controller can be fixed and that it is something simple, but it sounds like this is not your thing.

author: Richard_L
author_rank: Contributor
timestamp: January 29, 2017, 07:54:47 pm
content: Ah, so the only repair information already on the internet about this dehumidifier is probably nonsense! I did think that a resistor failing short rather than burning out and failing open was a bit odd but beyond that I hadn't even seen the actual control board when writing my question Thanks for the info about the start-up power of the motor looking reasonable.Now, since writing my original post I've had the time to take off the front panel off of one of the machines and can now see where the control board is located. It's screwed to the underside of the plastic shelf that divides the inside of the machine in two. The compressor and water collecting tank are in the lower half, the refrigeration coils, fan and humidistat are in the top half. I don't think that this was built with disassembly or servicing in mind because there's only a few centimetres of clearance between the PCB and the compressor. I'm going to need a really stubby screwdriver and some smaller hands to get the board out. At the moment I can't see much of what's on it beyond two X2 caps and a relay, much less start probing around it...

author: Seekonk
author_rank: Super Contributor
timestamp: January 29, 2017, 08:15:42 pm
content: I cringe at all the capacitor changers on this board, but it does seem likely that the main electrolytic on this board may be low in value. Being that close to the compressor heat could have caused this problem. It makes sense that the high current draw of the motor on startup lowers line voltage resetting the micro.