Garage Door Opener Fail - Page 1
Forum section: electronics / projects

author: calzap
author_rank: Frequent Contributor
timestamp: March 05, 2021, 05:34:50 pm
content: The opener is a Chamberlain 2000SDR residential garage door opener. It was installed in 1999. Two years ago, it lost its ability to link to new remotes. Gradually, one by one, it refused to respond to existing remotes to which it was linked. When it reached the point that there was only one usable remote, it was time to examine and perhaps change the PCB (there is only one).The PCB is in the main ceiling unit that also contains the motor, gears, limit switches, and light sockets. When removing the PCB, I was surprised at how the plastic in the main unit had deteriorated. A mere touch to some parts caused the plastic to crumble. Plastic in the old remotes is robust as ever.Pictures below show the front and back of the PCB. Front is all through-hole; back is all SMT. Board was mounted vertically with the large pin connector at the top. The pin connector carries in 120 VAC power and connects to the motor, limit switches and bulb sockets. The three screw terminals to the right of pin connector are for wires from the wall controller and the photoelectric sensor near the bottom of the door frame. The red, square button switch is used for linking remotes, and the yellow LED beside it indicates to the user when linking is occurring. The two pots with blue shafts are used to set reversal force in the down direction and stop force in the up direction … presumably this is done by monitoring increased current draw or decreased RPM of the motor.The big 28-pin chip in the middle of the front side is a Chamberlain custom chip and presumably is the controller. The 14-pin LM2902N is an op amp and is part of the receiver circuitry. The LM340T5 near the transformer is a 5 VDC voltage regulator. I presume the large white SPDT relay is for the motor, and the two smaller black relays are for the limit switches. The gray wire running off the right side is the antenna and is 23 cm long. The back side has resistors, capacitors, transistors, and an Atmel832 microcontroller. I’m guessing the Atmel chip, which is mounted directly under the Chamberlain chip, is being used primarily for flash memory storage, but it may have control functions as well.I looked for the common culprits of bulging caps and smoky, burned areas. Caps looked OK but there was smoke on the PCB in the upper righthand corner near the screw terminals. The smoke was around the two 201 ohm resistors and diode D16. The two resistors themselves looked OK and read exactly 201 ohms on the multimeter. Markings on the diode are 1N4, and it looked OK on close inspection. Using the diode check function of a multimeter, it read 0.718 V in one direction and zero volts the other, which sounds right. I’m guessing the two resistors were being run near their wattage limit (or above) which generated enough heat to singe the coating on the PCB. Soot around D16 was carried there by convection from the vicinity of the 201-ohm diode directly beneath it.So, I’m not sure what caused the failure ... but guess it was deterioration of the flash memory.Fortunately, I had a spare PCB. It was installed, and all work perfectly now.Mike in California

author: bgm370
author_rank: Contributor
timestamp: March 05, 2021, 06:29:47 pm
content: FWIW, I fixed a board like that not so long ago. The culprit was that large capacitor next to the voltage regulator. The 5v rail was completely unstable which lead to constant circuit resets.

author: kripton2035
author_rank: Super Contributor
timestamp: March 05, 2021, 08:02:49 pm
content: yes, measure the esr of the capacitor , or even change it directly.

author: floobydust
author_rank: Super Contributor
timestamp: March 05, 2021, 08:56:05 pm
content: Garage door opener boards are quite repairable. I find the parts that fail are:Electrolytic capacitorsRelays (motor, direction, lights)The soot around the parts is normal due to years of convection currents and dust buildup. They are powered 24/7 and any part that runs warm will look like that.OP's possibly needed the RF receiver tuned. I can see the board's RX tuning coil next to the LM2902. If you have the plastic hex tool to turn it (the ferrite slug is very fragile!) I'll mark it with a felt pen and give it a 1/4 turn in either direction to see what works. Of course you can use an SDR to pick up the local oscillator to tune it.There's 7 capacitors and a few by the RF receiver, so they could have died of old age.Note these boards don't like CFL or LED lighting, the bulb's radiated EMI can overwhelm the RX with noise. So the door opens, light goes on but then a remote has trouble closing it.I find the newer garage door opener are crappy - tiny motor, small plastic gears and the slowest door opening I've seen. Thin belt and frame.The Chamberlain's with WiFi authenticate to a central server in the USA so a security risk, the phone-app is convenient.

author: james_s
author_rank: Super Contributor
timestamp: March 05, 2021, 09:22:17 pm
content: That "smoke" is just dirt from the air. It collects like that due to convection currents from parts that get hot in normal operation.I would definitely check those capacitors, most of the time when they fail they show no visible signs. It is only when they are really hammered in something like a switchmode power supply that they heat up enough to bulge or vent.

author: calzap
author_rank: Frequent Contributor
timestamp: March 05, 2021, 09:28:41 pm
content: Thanks for the suggestions on the capacitor. So, I desoldered it, gave a tug, and off it came. Unfortunately, one of the leads stayed behind in its hole in the PCB. The lead was easily removed by tugging on it. No way to test the cap now. If the replacement PCB fails, then I’ll put a new cap in the old board and try it. It’s a big job to swap PCBs, especially with the plastic housing of the opener crumbling. So, I won’t do it unless I have to.Mike in California

author: james_s
author_rank: Super Contributor
timestamp: March 05, 2021, 09:41:23 pm
content: That's a pretty good indication that it was shot. It probably corroded off internally and the capacitor was no longer doing much if anything. In a normal capacitor you have to tug pretty hard to yank a lead out.

author: ImpulsiveJames
author_rank: Contributor
timestamp: May 07, 2022, 02:20:57 am
content: I literally just signed up to sayYOU GUYS MADE MY ENTIRE WEEK!!!!!I was having the same issue. One day both of our remotes just totally stopped working. No relearning codes or anything (but learning light would still blink). I didn't even think to test the cap over on the HV side of the board - doh. I used my crappy ESR meter on the old one and, "oh that's odd, 0.L".... Took it out of the board, same thing, no NF, no Ohms, no nothing. Finally found a 25v 330Ohm (Supposed to be 35v 330Ohm - oh well, it will last a week until I find a higher current one). Bingo, started working immediately!!!! Saved me 50 bucks on ebay and a week of waiting!Thanks again! You guys rock!!!!

author: james_s
author_rank: Super Contributor
timestamp: May 07, 2022, 05:38:29 pm
content: I'm guessing you meant 330uF, resistors are measured in Ohms, capacitors in Farads. Glad you were able to fix it, most of the time the whole opener probably gets junked over a 50 cent capacitor.

author: floobydust
author_rank: Super Contributor
timestamp: May 08, 2022, 12:59:28 am
content: It looks like a 330uF 35V filter capacitor, an easy repair for under a $1. You can also get replacement gears, motor caps and microswitches etc.Because the new models are pretty cheap, little toy brushed DC motor and slow as molasses opening. Don't get me going on the myQ phone app needing Internet access to HQ for authentication. So it's actually worth it to do the repair.