LG Plasma 50PC1DR- Y-SUS Issues

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

You can see he's cut the bond wires and replaced the MOSFETs/IGBTs inside the IPM with external FETs. Same idea here: http://www.youtube.com/watch?v=DGqH8LGjZdY

I have never done this before, it is all new to me - I expect that most IPMs will be compatible, as long as the pins fit, as there is little integral difference now between plasma panels. They all work in much the same way.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

But where are the mosfets on the original chip ? the little square plates with bonding wires ?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

ah got ya. so it's the square pads.. its just that it's not packaged. are the mosfets the main cause of ipm failure ? hell, i'd do it on the chips here just for the hell of it !!

i'm wondering, they're doing it with the j017-18, but is it the same with the j016 j015's ?
i mean, using the same mosfets ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

ah got ya. so it's the square pads.. its just that it's not packaged. are the mosfets the main cause of ipm failure ? hell, i'd do it on the chips here just for the hell of it !!

i'm wondering, they're doing it with the j017-18, but is it the same with the j016 j015's ?
i mean, using the same mosfets ?

Yes, if you take apart a bust IPM, you will find a large silicon substrate with individual FETs/IGBTs on it; the bond wires connect to them. It is the failure of these individual devices on the IPM which commonly kills LG plasmas. Which is the annoying part, because it usually condemns the whole IPM. I would expect that the designs are similar, just made by different companies.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

okay ! i have one that is bad here, that has just a little stain on one of the mosfets. very little.. but this ipm is dead. sometimes it burns and its clearly bad.. but sometimes its not very apparent it seems. no shorts when doing meter tests either..

adding a fan to the ER ipm's isnt a bad idea i think

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

hey hey ! another one bites the dust second working set. it's the yppd j016 from china (used) that was bad again. thanks for selling me non working chips, folks !!

used a 3rd one, from same batch, 50 inch joy. im getting better

for testing, ive used the ipm's without the heatsink.. those boards are getting a bit abused, ripped pads and such...

i was wondering, is there any way i could reliably fix the heatsinks AFTER having the ipm's installed, say, using some adhesive thermal compound, or just using some cyanoacrylate (crazy glue) on the plastic part where the screws goes ?

edit : i'm still searching for those 2 diodes i need.. the 4A 67 and the 25 one. I've seen your pdf tom66, but how can i figure out the voltage that i need for that 4a diode ?

the one marked 25 at d32, no clue what this one is either.

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Glad you fixed it. Can you post a pic of the mystery diode with a ruler for scale?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

um.. its probably about 1 or 2mm max ! it's very small, even smaller than smd resistors we see often, the smaller ones ! can you see d32 on the board ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Possibly a SOD523; can you point it out, is it definitely dead? Or just missing?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

it was shorted ! it's D32 on the board

see : https://www.badcaps.net/forum/attach...5&d=1347400258

straight in the middle of the picture !

also, see the diodes there.. 4a 67. how can i know their voltage rating ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

That looks like it might be a zener diode, because it is across a cap. It would short if a supply on the Y sustain went too high for too long. You can remove it temporarily and test it without the IPMs installed so you don't damage them as I think that provides the regulated 15V for them. If it is too high, you need to trace where the high voltage is coming from. Could be the 15V adjustment is set wrong (it can drift.)

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

okay. ive got no diode like that left, it was shorted on one of the ysus ive repaired already. so i got a board with none on it..

how can we figure out what a smd marking means ? it says 25.. ive tried to search a lot, but hell, didnt find much.. a lot of references on 25 but not with this package size

maybe i wasnt clear in the way i explained. i mean the board on which that diode shorted had a few shorts on it which i all resolved, a shorted fet etc.. now this one works

so the one missing that diode just needs a new one, all seems fine in that section of that board. the psu was full of 330uf 10v bad caps tho. that's the 3rd plasma of the same model

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Check the voltage across it. If it's a 15V nominal supply (I suspect it is) use a 20-22V zener diode like this...

http://www.digikey.com/product-detai...87-1-ND/790090

It's just to protect the IPM, or the rest of the board, when something goes wrong and the supply goes too high. Not sure a puny thing like that is going to do much good though, it would usually melt.

[tw2005]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Could it be a 4A and those other numbers are date code or batch. I have a bunch of 4A and below I can just make out actually 3 digits. mine are 541 on the 2005 board, 751 on the 2006 board.

would that be this PDF I attached to this post?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

would that be this PDF I attached to this post?

yes, but how do i choose which one would be better suited ? there's from 50 to 1000v dc there in the pdf. i can measure what's going thru it and choose anything higher ?

i only see 0.4 or so volts going thru this one :/

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Are you still looking for the diode - Can't you test across a board with one of those components on there?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

which one, the small one ? i tested and see 12vdc going across this one.

the bigger 4a one, i'm trying to understand what i need, the pdf posted by tw2005 seems to be of a good device, but i'm wondering what voltage do i need ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

What's the biggest you can get? :P There is no harm in installing one with too high reverse rating unless it is a zener.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

http://www.digikey.ca/product-detail...ITR-ND/1091483

that would be fine ? sorry to ask stupid questions, im really not safe ordering parts.. a bit scared of ordering the wrong one and creating more problems than i'm fixing !!

[tw2005]

Re: LG Plasma 50PC1DR- Y-SUS Issues

yes, but how do i choose which one would be better suited ? there's from 50 to 1000v dc there in the pdf. i can measure what's going thru it and choose anything higher ?

i only see 0.4 or so volts going thru this one :/

4A shows as 50V