Pn42c450 power cycling

[whatusername]

Hi Guys
I purchased this Samsung plasma on Craigslist as is and it powers on and about 5 min later shuts off the attempts to power on then shuts off then powers on again and will stay on for a few seconds then off and repeats.
I have inspected the power supply for bad caps and all look good i also looked for cold solder joints and saw 1 that appeared broken so i re soldered it but still same deal... i have also tried unplugging 1 board at a time x board y board and i guess t-con? board and main board and it still cycle loops. is it safe to assume it is a bad power supply? i do have a multi meter if needed i just do not know where to start. any help would be appreciated and any information u request i will do my best to supply.Thanks in Advanced

[tom66]

Re: Pn42c450 power cycling

When it turns off, does the sound cut out?
Tried tapping on things (with an insulated screwdriver handle) and see if you can make it cut out quicker -- help locate fault -- a hairdryer for heat can work too.

[whatusername]

Re: Pn42c450 power cycling

Yes when it turns off the sound goes with it its not just the screen going black the tv actually turns off then when it tries to restart the red led blinks once then it clicks and retries to start and 9 out of 10 times it does for a few seconds... no i didnt try tapping on anything with a screw driver where would i tap first?

[tom66]

Re: Pn42c450 power cycling

I'd start with the power supply heatsinks then the main and control boards.

[whatusername]

Re: Pn42c450 power cycling

ok i hit all heat sinks with the screw driver head and nothing happened at all i also took pics of the boards in case u need to see them

[whatusername]

Re: Pn42c450 power cycling

Here are the pics

[tom66]

Re: Pn42c450 power cycling

Can you try with a hairdryer instead and see if you can make it shut down quicker by heating up parts? Focus primarily would be on the main board, control board and power board as before.

[whatusername]

Re: Pn42c450 power cycling

i was actually just doing that i had the hair dryer on the power supply board on high and full heat and it did not shut off any faster than normal
i will try the blower on the other boards now
Also if you would take a look at these 2 450v caps on the power supply in the pics below although not bulging, when i look at them in the i guess marcedes sysmbol lines instead of it being all solid metal connected like the rest i can actually see what i believe to b the inside of the cap that cruddy stuff but i see it only in those lines. u can see it in the pics could they b bad?

[tom66]

Re: Pn42c450 power cycling

They look OK to me -- could just be dust.

[whatusername]

Re: Pn42c450 power cycling

u are correct i cleaned them with a paint brush and it was dust.. i hit the blower on the main board. I assume the idea is to over heat the component causing it to fail? if so the tv did shut off faster when i heated the main board and will not turn back on its just power clicking

[tom66]

Re: Pn42c450 power cycling

Wait for it to cool down and try again, but it seems like you have the common main board fault on this set.

[whatusername]

Re: Pn42c450 power cycling

i did and it definately shuts off much faster when i heat up the chip

[tom66]

Re: Pn42c450 power cycling

Great, lead free solder strikes again... you can attempt a reflow (ala Xbox 360 RROD/PS3 YLOD) but the best overall fix is a complete replacement of main board, and adding a heatsink to that chip.

[whatusername]

Re: Pn42c450 power cycling

ok i will order a board and post the results
Thank you very much Tom66 i appreciate your help

[whatusername]

Re: Pn42c450 power cycling

T board finally.came in i installed it and tv stays on. chalk up another one for Tom... good job mate... On a side note Tom i see ur in the UK.. do u know anyone in the Rfoc?

[sspoonmann]

Re: Pn42c450 power cycling

Same I replaced x sus board and panel blew it again. Bad panel