Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault
Good fix, thanks for the update.
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Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault
I'm chasing somewhat of the same issue. Started with a shorted cap at c204 between Vcc and gnd of Ic201 (200d6). replaced with a 50uf (original was 100) to check and everything worked for about 10min.
replaced Ic201 based on OP's xperiences as everything else seemed to test fine, as well as replacing C204 with the proper value.
Blew out the 2.0 ohm resistor and the driver FET Q202.
replaced those and IC201 again(as a precaution), and got fluctuating voltages on the high voltage pin of IC201 .
IC201 was showing high frequency bursts on the gate of the FET, and as I was continuing to probe it blew out the 2.0 ohm resistor and the FET again.
I've checked all around that area and components seem fine.
Any advice?
Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault
If i remember correctly I blew the same FET and resister once because I had the ic-201 removed from the circuit when I powered up the board. IF I remember correctly there is a small transformer located next to the IC-201, FET and resistor. Make sure incoming/outgoing voltage is good on that. make sure all connections and solder joints are good in the area also. A cold solder joint will cause some weird symptoms and have you chasing ghost.
Also remember there is a floating ground and a chassis ground on that board.
Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault
Thanks, I've given the board a good look over, but I'm sure my tired old eyes may have missed something.
I'll report back when I've had another go at it.
On the left and right they are C416/415 & C401/402 that seems similar to the couple C417/418.
The dielectric is light grey then the value could be low but also different because the height is not the same.
It is not for me but a colleague so I Don't have the board.
Re: LG 50PN4500 - fluctuating Vcc/18V supply on Y-sustain board causing fault
I do believe R_J is correct in saying they are .022uF and around 500v. The safest way to proceed would to just buy the repair kit. That way you will have the correct caps and plus you will have some spare parts in case you need them.
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