Appliance power problem

[SCar24]

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

 

[James]

Faulty plug or socket.
Loose connection on any part of the wiring.

 

[brianmoooore]

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.

 

[KungFuTurkeyLeg]

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.

 

[SCar24]

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 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.

 

[KungFuTurkeyLeg]

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.

 

[Avo Mk8]

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!

 

[mainline]

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 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.

 

[DPG]

Difficult to say without seeing it, but my money would be on a dried out electrolytic capacitor.

 

[brianmoooore]

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.

 

[SCar24]

Here are a couple of photos of the circuit board.

 

[KungFuTurkeyLeg]

Here are a couple of photos of the circuit board.

That resistor on the PSU should be about 10 ohms if I remember my colours.

Check for a dead short on the other board between ground and the components. I'd highly recommend watching NorthridgeFix on you tube for some good guidance on what you're looking for.

 

[Marvo]

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.

 

[brianmoooore]

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.

 

[DPG]

If I was a betting man I'd say C1.

 

[Marvo]

If I was a betting man I'd say C1.

Good job it doesn't need an EICR

 

[mainline]

You need a multimeter really to check any 000 resistors and also to do some voltage measurements.

After you solder any dry joints of course.

 

[DPG]

You need a multimeter really to check any 000 resistors and also to do some voltage measurements.

After you solder any dry joints of course.

I'd say the caps are more likely to have failed, but without substituting them you can't really tell. Unless you have an ESR meter, which the OP won't have.

 

[Avo Mk8]

Or there's the option of ~£38 for a replacement board plus ~£40 to ship it to UK

Power Board, 0.8 W 041A4023

www.shopssl.de

 

[mainline]

I'd say the caps are more likely to have failed, but without substituting them you can't really tell. Unless you have an ESR meter, which the OP won't have.

Lots of multimeters will test capacitance which will give a general idea of if it’s faulty.
You don’t need an esr meter to test a capacitor there are other ways an esr meter is not a definitive test.
Personally I would be doing some voltage and resistance measurements rather than just changing components in the hope it cures the fault.

 

[DPG]

Lots of multimeters will test capacitance which will give a general idea of if it’s faulty.
You don’t need an esr meter to test a capacitor there are other ways an esr meter is not a definitive test.
Personally I would be doing some voltage and resistance measurements rather than just changing components in the hope it cures the fault.

Faulty caps often show a good capacitance figure unfortunately. Take it from someone who has spent years in the electronics repair industry. An ESR meter is an excellent way to test if the cap is actually good.

And yes, testing is the way to go, but the OP is probably not competent enough to do live testing on a power supply.

 

[mainline]

Faulty caps often show a good capacitance figure unfortunately. Take it from someone who has spent years in the electronics repair industry. An ESR meter is an excellent way to test if the cap is actually good.

And yes, testing is the way to go, but the OP is probably not competenenough to do live testing on a power supply.

But you think that he’s competent enough to de solder and replace electrolytic capacitors without putting one in the wrong way around .

All those years in the industry I would have thought you would use an Lcr meter as they use a higher frequency than Esr ones

 

[DPG]

But you think that he’s competent enough to de solder and replace electrolytic capacitors without putting one in the wrong way around .

All those years in the industry I would have thought you would use an Lcr meter as they use a higher frequency than Esr ones

An LCR meter won't tell you the effective impedance of a capacitor - it's 'goodness' in effect. You can have a cap reading spot on capacitance, but it can be next to useless.

An LCR meter is no different to a multimeter with a capacitance range as far as measuring caps goes. It measures inductance (L), capacitance (C), and resistance (R).

An ESR meter is a different thing alltogether.

And replacing components or re-soldering joints is much safer than testing a live power supply!!

 

[mainline]

An LCR meter won't tell you the effective impedance of a capacitor - it's 'goodness' in effect. You can have a cap reading spot on capacitance, but it can be next to useless.

An LCR meter is no different to a multimeter with a capacitance range as far as measuring caps goes. It measures inductance (L), capacitance (C), and resistance (R).

An ESR meter is a different thing alltogether.

And replacing components or re-soldering joints is much safer than testing a live power supply!!

LCR meters are measuring instruments that measure a physical property known as impedance. Impedance, which is expressed using the quantifier Z, indicates resistance to the flow of an AC current. It can be calculated from the current I flowing to the measurement target and the voltage V across the target’s terminals. Since impedance is expressed as a vector on a complex plane, LCR meters measure not only the ratio of current and voltage RMS values, but also the phase difference between current and voltage waveforms.

While all LCR meters offer readings of inductance, capacitance, and resistance, higher-end meters will also provide additional measurements. These options typically include impedance (Z), phase angle (θ), conductance (G), susceptance (B), dissipation factor (D), quality factor (Q), and equivalent series resistance (ESR).

 

[DPG]

LCR meters are measuring instruments that measure a physical property known as impedance. Impedance, which is expressed using the quantifier Z, indicates resistance to the flow of an AC current. It can be calculated from the current I flowing to the measurement target and the voltage V across the target’s terminals. Since impedance is expressed as a vector on a complex plane, LCR meters measure not only the ratio of current and voltage RMS values, but also the phase difference between current and voltage waveforms.

Irrelevant to my original point about ESR meters where you said they only need a multimeter.

 

[mainline]

It’s relevant where you said Lcr meters are not different to a multimeter or where you said a Lcr meter won’t tell impedance of a capacitor where in fact a decent Lcr meter will do everything that a decent Esr will do plus a lot more.

The op is more likely to have a multimeter with a capacitor tester than an esr meter I did say a capacitor test generally works and that a esr meter test is also not definitive as most Esr meters won’t test at some frequencies that Lcr meters will.

 

[DPG]

It’s relevant where you said Lcr meters are not different to a multimeter or where you said a Lcr meter won’t tell impedance of a capacitor where in fact a decent Lcr meter will do everything that a decent Esr will do plus a lot more.

The op is more likely to have a multimeter with a capacitor tester than an esr meter I did say a capacitor test generally works and that a esr meter test is also not definitive as most Esr meters won’t test at some frequencies that Lcr meters will.

My point remains, ie. The best the OP will have is a multimeter. If it has a capacitance range then he can measure the capacitance values. But be can't measure the ESR of the capacitors, and so cannot tell if they are OK or not.

So the only way he will know if the capacitors have failed is to change them. And having fixed many SMPSUs in my time I can tell you that it's a pretty likely fault. Unless the power supply has failed catastrophically of course, but this one hasn't - it's just not always starting up.

The LCR bridge is just a distraction to be honest.

 

[mainline]

My point remains, ie. The best the OP will have is a multimeter. If it has a capacitance range then he can measure the capacitance values. But be can't measure the ESR of the capacitors, and so cannot tell if they are OK or not.

So the only way he will know if the capacitors have failed is to change them. And having fixed many SMPSUs in my time I can tell you that it's a pretty likely fault. Unless the power supply has failed catastrophically of course, but this one hasn't - it's just not always starting up.

The LCR bridge is just a distraction to be honest.

If the capacitance measures bad then the cap is bad. If the capacitance measures good... Then the cap still might be bad.

If the esr measures bad then the cap is bad. If the esr measures good... Then the cap still might be bad.

If the leakage current measures bad then the cap is bad. If the leakage measures good... Then the cap still might be bad.

Pretty simple really and it’s not just about the lcr bridge as I said previously it’s also about frequency.

 

[DPG]

If the capacitance measures bad then the cap is bad. If the capacitance measures good... Then the cap still might be bad.

If the esr measures bad then the cap is bad. If the esr measures good... Then the cap still might be bad.

If the leakage current measures bad then the cap is bad. If the leakage measures good... Then the cap still might be bad.

Pretty simple really and it’s not just about the lcr bridge as I said previously it’s also about frequency.

Fair enough. You win

But whenever someone next brings me something to repair that's a few years old I will check the caps with my trusty old ESR meter and no doubt find a couple of duff ones.

 

[SCar24]

Thanks for all your great responses and advise here guys, this is turning into a challenge now to see if I can find the fault If it goes to h*** then there's always Avo Mk8's tip with the replacement board.

 

[Avo Mk8]

Thanks for all your great responses and advise here guys, this is turning into a challenge now to see if I can find the fault If it goes to h*** then there's always Avo Mk8's tip with the replacement board.

There is a UK company selling them as well, but I was sceptical that they might be pricy - worth asking maybe?

Chamberlain Power Board, 0.8 W

Garage Door Openers Spares for Chamberlain, Liftmaster & Motorlift for the Trade Supplier. 0.8W

www.easygatesdirect.co.uk

 

[mainline]

Fair enough. You win

But whenever someone next brings me something to repair that's a few years old I will check the caps with my trusty old ESR meter and no doubt find a couple of duff ones.

As long as the capacitor is an electrolytic and isn't of too low a value