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Equipment Repairs => LCD TV forum => Topic started by: markie76 on November 25, 2009,20:15:56

Title: Clicking power supply
Post by: markie76 on November 25, 2009,20:15:56

Hi Guys,

My Technika LCD26207 has refusedto switch on.

When you press the on button the blue LED lights up then the power supply starts to click, like its trying to switch on but something isn't holding and it clicks, click, click, click, length varies around 1 second.
It also has a medium pitch frequency whine, which varies between the clicks.

The power supply is PW22-4 which I believe is a common part - OEM vestel and fitted in all sorts of marks.

Taking a closer look & listen, it sounds as if the noise is coming from the black circular transformer which sits between the live & isolated side and is marked 30053742 SMP-C1793 VDE.

Any ideas?

Thanks,

Mark.

Title: Re: Clicking power supply
Post by: markie76 on November 29, 2009,07:10:03

come on - someone must have some sort of idea? - I can't be the first person in the history of televisions to be experiencing this especially as this power supply is used across multiple brands/models of LCD tv...


this is forum is supposed to be full of experts???

Title: Re: Clicking power supply
Post by: sparky on November 29, 2009,09:51:02

you must check the voltages first to see whats missing
you just can't think the solution will jump out

Title: Re: Clicking power supply
Post by: markie76 on November 29, 2009,12:10:35

Hi Sparky,

Yes you're right - this is the second psu of this model I have come across with the clicking symptoms I assumied it must be common and known as these seem to as common as sliced bread in the budget to mid price lcd tv's.

Can you expand on measuring the voltages? I'm not a repair specialist but tinker in electronics and without a service document - all I'd be doing is guessing.

Thanks,

Mark.

Title: Re: Clicking power supply
Post by: Turnip on November 29, 2009,12:23:54

Hi Mark,

  Have no info relating to your problem, but suspect that a repeated ticking might indicate a secondary short somewhere, suggest checking (with power off) cathodes of secondary diodes to chassis with a meter for shorts, and replace any bulging capacitors.

  What was the problem with the first one ?   - Chris.

  Generally, secondary power supply voltages are 5v, 12V and 24 V for the backlights, often marked near the PCB output sockets.

Title: Re: Clicking power supply
Post by: markie76 on November 29, 2009,17:43:50

I now remember why I have never measured the voltages....because they are not marked up - all the connectors are numbered and I guess you need to have the circuit diagram/service manual to find out what is where.

Does anyone have a schematic for a 17PW22-4 PSU or similar?

The capacitors have always been fine on these PSU's I've seen. The two I have both have a buzzing/high frequency whine and intermittent clicking (one clicks constantly the other clicks sometimes at varying intensity in between high pitched whine) and it seems to come from the component circled in red.

Title: Re: Clicking power supply
Post by: markie76 on January 31, 2010,15:09:40

OK, I have found time to measure the output voltages and they all seem fine - generally above the rated voltage by 0.5-1.0 v (I don't have the exact values on me)

This is such a newbie question;

Do you measure voltages under load or not? IE with all connections in place on the PSU connectors?


Thanks,

Mark.