LG power supply

[Cohibaman]

I'm recapping the PS in a 37" LG LCD TV. LG used the same board on the 37" & 42", but only populate the board with one 150uF/450V cap on the 37" PCB and used two on the 42" PCB.

I ordered a new Panasonic 220uF/450V, but got to thinking, would I be better off replacing the 150uF with the panny and call it a day or should I add it for a total of 370uF? I'm not sure how good that'll be paralleling dissimilar ESRs like that.

[paulstef]

Re: LG power supply

If the original was 150 why would you put in 370?

Use the 220 and that's it.

Anyway, if you add low esr caps somewhere I wouldn't worry about them having dissimilar esr values.

[Cohibaman]

Re: LG power supply

If the original was 150 why would you put in 370?

Use the 220 and that's it.

Anyway, if you add low esr caps somewhere I wouldn't worry about them having dissimilar esr values.

Because they cheaped out on the 37 inch and only put in one of the two caps. The primary xfmf is the same and rest of the components appear to be the same as well.

[budm]

Re: LG power supply

42" uses more power. Higher capacitance will have higher surge current so more stress for the bridge, did you check the fuse size and the bridge rectifier rating of the 42"?

[Cohibaman]

Re: LG power supply

I stand corrected. The 37" high voltage output is 1325V versus 1440V on the 42", so obviously there are a few other component changes besides an additional 150uF filtering cap. I'm just going to replace the single 150uF with the 220uF Panny.

Thanks!

[stj]

Re: LG power supply

just fit a pair of 220's and your good.

[budm]

Re: LG power supply

What are the amp rating of the main fuse for the 37" and the 42"

"just fit a pair of 220's and your good." so from ONE 150uF to 440uF? That is about 3 time the original value. He better check the surge current first.

[Cohibaman]

Re: LG power supply

just fit a pair of 220's and your good.

Well that was my thinking as well since the only stress the bridge will see is when I first plug it in. From there, the switcher is powered 24/7/365 and any additional capacitance will not cause additional stress.

But I only ordered one cap so at this point I'm only going to use the one 220uF panny.

But I still want to know theory; would two dissimilar filter caps in parallel on the high voltage be an issue?

[Cohibaman]

Re: LG power supply

What are the amp rating of the main fuse for the 37" and the 42"

"just fit a pair of 220's and your good." so from ONE 150uF to 440uF? That is about 3 time the original value. He better check the surge current first.

Both use the same pair of 5A & 8A fuses.

[budm]

Re: LG power supply

"Well that was my thinking as well since the only stress the bridge will see is when I first plug it in." That is not true because the PFC Voltage is not always running, the Voltage is boosted from 160VDC to >360VDC when TV is turned on so you will stress the bridge, the PFC Diode, the PFC MOSFETs, so take your chance on that.

[Cohibaman]

Re: LG power supply

"Well that was my thinking as well since the only stress the bridge will see is when I first plug it in." That is not true because the PFC Voltage is not always running, the Voltage is boosted from 160VDC to >360VDC when TV is turned on so you will stress the bridge, the PFC Diode, the PFC MOSFETs, so take your chance on that.

Good to know, thanks!

[stj]

Re: LG power supply

ah, but what is the ripple capacity of the old cap(s) vs the new one???

[Alastair E]

Re: LG power supply

Stick to the Original Value component, with the Same ratings....

Why try and Second guess what the maker has done--with the possibility of causing issues down the road with the set.

IF this is a customer set and a repair with a charge--What happens if (For some unknown reason--maybe even unconnected with your repairs) the set causes a fire or other life-threatning issue?

You as the last repairer--could be liable, and some shyster-lawyer will have a field-day with ya!
.....

[Cohibaman]

Re: LG power supply

This is getting more model specific than I originally thought - could a mod add MODEL NO. 37LC7D to the thread title please?

[budm]

Re: LG power supply

Stick to the Original Value component, with the Same ratings....

Why try and Second guess what the maker has done--with the possibility of causing issues down the road with the set.

IF this is a customer set and a repair with a charge--What happens if (For some unknown reason--maybe even unconnected with your repairs) the set causes a fire or other life-threatning issue?

You as the last repairer--could be liable, and some shyster-lawyer will have a field-day with ya!
.....

Yeah, just like this guy here that blew up LEDs with 120VAC, and now this:
https://www.badcaps.net/forum/showth...162#post552162

[Cohibaman]

Re: LG power supply

Why try and Second guess what the maker has done--with the possibility of causing issues down the road with the set.
.....

I second guess the makers all the time with their crappy cap selection...

But yes, I agree with you on not straying too far with the values. It's a personal TV btw.

[Cohibaman]

Re: LG power supply

**Update** I replaced all the caps in the power supply with Panasonic and only used one 220uF/450V to replace the original 150uF/450V (I left the second cap location remain unpopulated as it was from the factory). It fired right up and has been working great for 7 weeks. Another LCD saved from the landfill.