Samsung SMPS for LCD TV

[lindemose]

Hi all,

This is my first post on this forum so bear with me if anything is missing...

My Samsung LCD SMPS gives me some headache.
I have attached a picture below:

The 24V line never reaches 24 volts but are stuch at 12.4 V and the F9222L does not compensate for this correctly, some how there is an error in the feedback mechanism in play.

I have also attached the schematics for this particular SMPS. There is a known typo on page 2, yje opto-couple is NOT attached to the 13V line as indicated but to the 24 v line.

The standby-by power of 6 V oand the power on/off circuit is running, but 12V, 13 V and 24V is all stuck at 6 V.

Any idea as to where the fault is ?

Best Regards
Lars

[japlytic]

Re: Samsung SMPS for LCD TV

Welcome, lindermose!
Sometimes, bad capacitors can show no signs of bulging or darkening (I've seen that more than once) and can drag a rail down due to reduced capacitance.

[lindemose]

Re: Samsung SMPS for LCD TV

Hi Japlytic,

That is correct and this remedy was the first i tried out. However i have only replaced all electrolytic caps. Maybe i should replace all once......... i'll try this out and get back with an update.

[lindemose]

Re: Samsung SMPS for LCD TV

Have replaced all caps both Electro, film and ceramics, no change !

also I saw that the F9222L power circuit was replaced by some other members with succes I will order one and replace it.

[budm]

Re: Samsung SMPS for LCD TV

Since this power supply has PFC, check the DC voltage on that large 450VDC cap when the TV is plugged in but not turn on, it should have 325VDC (230VAC X 1.414) at its two legs, then turn it on, the DC should go up to around 400VDC Iif the PFC is working.

[lindemose]

Re: Samsung SMPS for LCD TV

Since this power supply has PFC, check the DC voltage on that large 450VDC cap when the TV is plugged in but not turn on, it should have 325VDC (230VAC X 1.414) at its two legs, then turn it on, the DC should go up to around 400VDC Iif the PFC is working.

The DC voltage vas off by 15 V, it read : off = 310V and ON = 385V. Since there is a difference in ON/OFF voltages I take it as the PFC is working.....

[imp]

Re: Samsung SMPS for LCD TV

Is that a CapXon capacitor I see on the first picture? (the 450V one)

[rogfanther]

Re: Samsung SMPS for LCD TV

The resistors ( and the KA431A chip ) are ok ?

[lindemose]

Re: Samsung SMPS for LCD TV

Yes, that part of the circuit is working and the voltages ON/OFF and STBY is correct.

[lindemose]

Re: Samsung SMPS for LCD TV

Is that a CapXon capacitor I see on the first picture? (the 450V one)

No, I dont see any markings on it. It is a film type and the value is within 5% of the 150 UF, thus I think it works....

[imp]

Re: Samsung SMPS for LCD TV

No, I dont see any markings on it. It is a film type and the value is within 5% of the 150 UF, thus I think it works....

Sorry, I meant the large electrolytic one What manufacturer is it?

[lindemose]

Re: Samsung SMPS for LCD TV

Sorry, I meant the large electrolytic one What manufacturer is it?

It's a CapXon allright. Your keen eyes serves you well

[imp]

Re: Samsung SMPS for LCD TV

It's a CapXon allright. Your keen eyes serves you well

Hehe .... Actually, CapXon is the only manufacturer so far that I had failures with regarding high voltage capacitors, typically drying out. I´ve exchanged several of them in both PC PSU´s and Samsung TV:s. If you don´t have a voltage of 230 * 1,414 = 325 VDC (with some tolerance) all the time, this capacitor might be dried up. I wouldn´t do anything more before replacing all CapXon capacitors, they are among the worst out there.

[tom66]

Re: Samsung SMPS for LCD TV

I have also seen Samxon primary capacitors fail.

Samsung is one of those manufacturers regarded as good, despite using CapXon capacitors... must be good marketing.

[imp]

Re: Samsung SMPS for LCD TV

Samsung is one of those manufacturers regarded as good, despite using CapXon capacitors... must be good marketing.

They make TV´s with good picture quality but they simply don´t last when they use crappy capacitors.

[lindemose]

Re: Samsung SMPS for LCD TV

I recieved the replacement chip F9223L today and replaced the expected faulty F9222L.
This did the trick !
all voltages are nominel and later I will reinstall the SMPS into the TV and hopefulle it all turns out well.

[imp]

Re: Samsung SMPS for LCD TV

Great!

But you will of course change all the CapXon's any way...?

[budm]

Re: Samsung SMPS for LCD TV

Thanks lindemose for the reports, I will have to find the way to verify that F9222L in the future.

[lindemose]

Re: Samsung SMPS for LCD TV

The 450 CapXon will NOT be changed - not now anyway - the costs of a single high power cap i ridiculous thus i will keep the original.....
ALL other elctrolytic caps on the schematic has been replaced though..

[lindemose]

Re: Samsung SMPS for LCD TV

Thanks lindemose for the reports, I will have to find the way to verify that F9222L in the future.

Do you have any schematics of F9222L ? The ones i have seen is rudimentary and have no information on nominel voltages or such....

BR Lars