Samsung LN-T4665F bad PFC caps, what series to replace with?

[lookimback]

As the title says, I have a bad PFC cap, and it's the first time I've ever encountered a bad one. It's a 450wv 150uf. I usually go with Panasonic FC, FM, or FR. I can't find any in those series though, so I'm not sure what to get. There's actually 2, but only one looks bad. Should I replace both? Lead spacing is 10mm, diameter is 35mm. There's room to play though.

[Agent24]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

If one died the other is probably on its way out. In any case it sounds like a bad brand as it looks like these guys had the same problem with Samwha capacitors too: https://www.badcaps.net/forum/showthread.php?p=494827
https://www.badcaps.net/forum/showthread.php?t=10001

You won't find the value\voltage in a Low ESR series as primary capacitors are not typically Low ESR types.

Make sure you check voltage on them and discharge if needed before putting your fingers\soldering iron near their leads when removing.

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Yeah, these are Samwha too. I think the same series as in the link you posted. HZ series. I figured it'd be wise to replace both. I'd sooner do it right the first time.

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

So, general purpose caps are OK?

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

These OK?

http://www.digikey.com/product-detai...C30-ND/2428153

[Agent24]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Probably, if the replacement is the same size or bigger it should be just fine. To be paranoid, you could check the Samwha datasheet and check ripple current rating but HZ is not listed here: http://www.samwha.com/electric/produ....html?f_num=40

In fact neither is LP series that was used in the other thread. Presumably they are custom ordered ones or a discontinued series.

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

I couldn't find a data sheet for them earlier when I looked. And, being that Hz is the abbreviation for Hertz, Googling it seems impossible.

[Agent24]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Without knowing the specification it might be smart to use whatever will physically fit and has the highest ripple handling you can find.

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Ordered them already. Digi-key didn't have much selection, in stock anyway. Unless I'd went with a different can size, maybe I should have. They're rated 10000 hours @105°, ripple current 790mA. My understanding of the ripple current rating was backwards, I'd mistakenly thought the lower the rating, the better.

[Agent24]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Ordered them already. Digi-key didn't have much selection, in stock anyway. Unless I'd went with a different can size, maybe I should have. They're rated 10000 hours @105°, ripple current 790mA. My understanding of the ripple current rating was backwards, I'd mistakenly thought the lower the rating, the better.

No. The ripple current rating is like the voltage rating, the higher the number the more it can handle. If you go below what the original was, or rather, below whatever the circuit expects the capacitor to be able to handle, the replacement capacitor lifespan will likely be shortened as it tries to cope with more ripple than it can handle, which will result in higher operating temperatures.

ESR is the one that is typically better when lower, although depending on the circuit this is not always the case.

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

I'm going to call Digi-key and see if I can change it to these ones.

http://www.digikey.com/product-detai...1676-ND/483274

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

I got through in time and changed them.

[Agent24]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Looks better - and cheaper too.

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

I like cheaper.

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Thanks for the help too.

[electricboyo]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Large high-voltage electrolytic capacitors (such as 150uF 450V) normally have a much longer life than the lower voltage capacitors located in power supply secondary circuits.

Therefore, whenever a PFC capacitor fails, it is important to search for faults in the power supply which might have caused over-voltage on the PFC capacitor. Other posts on this forum have confirmed that a failure in the PFC circuit can cause the voltage across the PFC capacitor to rise up to 600 volts or higher, which (not too surprisingly) will cause even a high-quality brand-new capacitor to fail very quickly.

PFC circuits actively regulate their output voltage. Therefore the most important test is to measure the DC voltage across the 450V capacitor after replacing it. If the PFC voltage regulation circuit is working properly, this should be roughly between 350V and 380V when the TV is powered on (displaying a picture with backlight illuminated).

The PFC voltage should be measured both with the TV powered on and with the TV powered off. In many TV set designs, the PFC active control circuit will switch off when the TV is powered off. In this case the voltage across the PFC capacitor should decrease to a value of 150 to 170 volts.

Most PFC circuits conform to the manufacturer's recommended circuit for the controller IC. The ST L6561D and L6562D are 2 PFC controllers that are frequently used. There are several high-value resistors in the feedback loop. This is what determines the output voltage. Sometimes one or more of these resistors will fail "open circuit." In that case the output voltage on the PFC capacitor will rise uncontrollably.

Hope this helps!

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Helps a lot. Thanks. When the new caps arrive, I will be certain to check the voltage across them, and then go from there. This TV would actually turn on and work fine, but would start squeeling after a couple minutes. I also have two 25v 2200uf caps which are bulged and leaking.

[electricboyo]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

LCD tv sets contain multiple regulated power supplies: These certainly DO interact with each other. For example, your faulty 2200uf/25V caps could interact with the PFC controller in such a way that the voltage on the 450V cap might become unstable or become too high.

Don't forget the small electrolytic capacitors either: It's best to either test them all with an ESR meter, or (since small caps are cheap) replace ALL of them.

I went around the block several times with a Magnavox 32MF231D: A voltage regulator IC chip L5973D repeatedly failed (burned up/smoked). This happened AFTER I had carefully replaced all of the bulged/leaky caps on the power supply PC board.

The IC was failing because a nearby 100uF/25V SMT cap on the scaler PC board had high ESD. But this bad cap didn't "look" bad physically. In fact, because it was electrically in parallel with other capacitors, I didn't discover its high ESD until after I removed it from the PC board so that I could test it "out of circuit."

[lookimback]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

I know the exact IC you are talking about. I had the same problem and never figured it out.

https://www.badcaps.net/forum/showthread.php?t=31603

[electricboyo]

Re: Samsung LN-T4665F bad PFC caps, what series to replace with?

Yes, I solved the exploding L5973D issue:

Re: magnavox 32mf231d/37 no power backlights flicker

My solution:

Often the 16V to 12V regulator IC at location 7003 on main (scaler) PC board will be burned, cracked, or have a small hole near pin 7.


The part # for this IC is L5973D. It is on the back side of PC board: To see it the main PC board must be removed from TV set. Testing will show 16V input to this IC, but its output pin will be 0V instead of 12V. This prevents the TV from switching all the way into the "on" state. The backlight inverters may partially turn on, which will cause flickering backlights.

I suspect the L5973D fails because capacitor 2002 (100uF 25V SMT electrolytic) has high ESR. This cap is mounted on the front side of main PC board. It filters the 16V DC rail input to the L5973D IC. Perhaps the IC gets into an unstable state during power-up if this input capacitor has excessive ESR?

In the case of my Magnavox 32MF231D the initial problem was "TV totally dead." I found several bulged/leaking/failed capacitors on its power supply board. I replaced those.But within 1 minute of powering up the TV after recapping the power supply PC board, the L5973D on the main board smoked!

Unfortunately it's quite difficult to remove the failed L5973D without damaging the PC board. That makes it twice as important to make sure that the replacement L5973D survives!

I've tested a couple of 32MF231D main boards that I repaired by replacing both L5973D (7003 on PC board) and 100uF 25V cap (2002 on PC board). Both boards are continuing to work perfectly. In fact, this TV set is now in my den and my family uses it every day

-EB