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

 

[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.