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Appliance power problem

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SCar24

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Hi all,
I have a garage door opener that is acting a bit weird and was hoping someone might be able to shed some light on why this is happening?

Liftmaster garage door opener has a power board(WZA27289) that supplies power to the transformer. The problem is that sometimes when it is plugged into the mains the opener does not come to life, but if I take the plug out and in again a couple of times it lights up. So if for instance there is a power outage, the opener might not work, but after doing the unplug/plug in routine it starts working again.
Have checked the board for physical damage, but it looks fine.

What could be the cause of this behaviour?

Cheers,
Sean
 
Could be a faulty PSU for the supply to the door's remote control receiver. Usually a resistor gone high in value or a dropper capacitor gone low.
No experience of this wit garage doors, but I've come across it many times with TVs, back when they were worth repairing.
 
Some PSUs will cut off the output if it picks up a short or something it doesn't like. I have a couple of plug in transformers that shutdown and won't do anything until they have been unplugged and then energised again. Could also be as mentioned, faulty plug socket or garage opener itself.
 
Thanks for the replies.

Seems to be something internal on that particular board as I have tried with one from another garage opener that eliminated the problem and it worked fine.
Was just curious what would make a component not work one minute, then aha, I know what I'll do, I'll plug it in again and then it should be fine:blush: The capacitors are easy enough to replace, but the resistors would be a bit fiddly. In any case, I have no idea which ones could be the culprit.
 
Unfortunately without schematics and parts lists, etc or a known good unit to compare reaults, you're usually guessing. Short of an obvious skid mark on the board from a blown component or bulging cap with markings on.

There is a guy in YouTube that is good to watch if you get bored and want to tinker with circuit boards, his channel is Northridge fix.
 
Was just curious what would make a component not work one minute, then aha, I know what I'll do,
It's not so much a component works one minute and not another. It's that the component (or several) change their electrical value/characteristics over time and that affects the operation of the circuit, making performance marginal (or non existent!)
A trick with TV's etc. many years ago was to squirt suspect components with freezer spray to see if anything changed!
The capacitors are easy enough to replace, but the resistors would be a bit fiddly. In any case, I have no idea which ones could be the culprit.
If you want to try the scattergun approach to fault finding, try changing electrolytic capacitors (the ones in cans, or 'beads', and marked with +,- polarity) for new of similar value and same or greater working voltage (if you are lucky enough to find that info on the part or the pcb)
It could be something else, and the above will make no difference!
 
Last edited:
Thanks for the replies.

Seems to be something internal on that particular board as I have tried with one from another garage opener that eliminated the problem and it worked fine.
Was just curious what would make a component not work one minute, then aha, I know what I'll do, I'll plug it in again and then it should be fine:blush: The capacitors are easy enough to replace, but the resistors would be a bit fiddly. In any case, I have no idea which ones could be the culprit.
Can you post a pic of both sides of the board.
 
Difficult to say without seeing it, but my money would be on a dried out electrolytic capacitor.
I'd agree with that, if there's no sign of physical damage, such as burnt components.
You could also try typing model numbers and part numbers of things like the circuit board into the internet.
I had a fairly new washer/drier fail on me a few years ago. The main circuit board had a large, burnt and unidentifiable resistor on it, which was obviously a symptom of the fault, rather than the fault itself. Typing the part number of that board into Google led me to a website all in Chinese, but with a pic of the same circuit board as mine, with four red arrows pointing to four components on the board, including the burnt resistor. Next to that pic was a pic of a small plastic bag with the four components in it, and a link to AliExpress.
Two weeks later, the parts arrived (postage was more than the parts), were fitted, and the machine has been faultless ever since.
 
Before you load up the parts cannon try remaking all the solder joints on the through hole components with a little bit of fresh solder. Some of them look suspect especially around where the AC IN and LOAD sockets are.
 
There are several resistors on that circuit board. One, the one on the top side of the board is many times the physical size of the others, and there's a reason for this. The reason is that it passes sufficient current to get warm or even hot.
The constant heating and cooling stresses its solder joints, so large resistors should always be amongst the first components to be reflowed with solder. The heat given off by the resistor can also have a detrimental effect on susceptible nearby components, such as the adjacent electrolytic capacitor, C12, which may have dried out.
Note that the large resistor is quite likely to be a special fusible safety type, and should only ever be replaced with the correct type.
 

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