garsh
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Jan 17, 2013, 2:30 AM
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Samsung Plasma 42" 720p - Model PN42C450B1D - No Video
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Hi TV Forums. I'm going to copy all my information from reddit here:
Hey all,
I was told I should try my efforts here. You can see my original post in /r/fixit here: http://www.reddit.com/r/fixit/comments/16ii81/samsung_plasma_42_720p_model_pn42c450b1d_will_not/
Old Info: ==================================================================
I have this Samsung Plasma 42" 720p (Model #: PN42C450B1D). My brother's friend found it being thrown out and wanted to see if I could fix it. I immediately thought it may just be blown capacitors, but when I took off the back to investigate, I did not see any capacitors that looked bad/bulging. I also have not seen (though need to look more thoroughly) any scorch/burn marks.
So essentially, I am trying to figure out where the fault is and if it will be salvageable.
Weird thing is, the power board appears to be getting power as indicated by my AC voltage detector. However, there is no clicking going on and no LED or lights that turn on.
What is really strange is, if I leave the TV hooked up with just a power cord and apply my AC Voltage Detector to the chassis (metal framing) or anywhere on the TV, it goes off. However, as soon as I plug my HDMI cord from the TV to my laptop, the AC Voltage Detector stops going off.
Is that normal? Or could it be an indication of improper grounding/short?
I am not dead-set on getting this device to work, but playing around and trying to fix electronics is always interesting.
Thanks for your help! If you need any pictures/further info, please just ask!
EDIT: Upon further review, it does seem that there is a fuse missing. It requires a 3.15A 250V fuse. I'll have to wait to pick one up from RadioShack tomorrow, but until then could someone answer the following: What is the difference between slow and fast fuses? Also, is there an advantage going with ceramic over glass fuses? It appears the power board used ceramic, but I was not sure if so long as the rates are the same, if I could use a glass one without issue.
I tried linking the missing fuse area, and now the TV is clicking like it is trying to turn on. Will have to wait till tomorrow for further investigation. ====================================================================
Newest Info: + Album of pictures: http://imgur.com/a/Pi4wJ
Since then, I purchased a fuse with the correct rates and popped it in the power board. Now I start getting clicking when plugging the unit in or trying to turn it on!
I then started doing a voltage test on the different components. I think I may have found the issue at hand, but I would need one of you to confirm whether or not this is normal operation for a TV. So if you look at this image (http://i.imgur.com/na9msh.jpg) you can see the two components I believe to be the issue.
Issue #2 - If I unplug this board's connection to the power board, the TV turns on and I can get sound from HDMI input through my laptop. So, because of that reason, I'm thinking it may be shorting out or something is defective/broken with Issue #2.
Issue #1 - If I unplug Issue #2 from power board and test the voltages coming from the power supply board to that Issue #2, I initially get the correct voltages as indicated on the sticker chart. The issue is, the voltages to not remain constant. After the TV is initially turned on, the voltages will drop at/near zero. This is what I want to know for this situation: Is that normal operation? I would be under the impression that capacitors on the board could store energy, and as a result voltages may drop as the same amount is not being pushed through, but I definitely wouldn't think they would drop to zero. I'm beginning to think this may be the actual issue: BAD POWER BOARD.
What do you all think? Is it Issue #1? or Issue #2? Or do I need to perform further testing? Please let me know if you need additional information/pictures. I'm more than happy to give them.
I do not believe I have tested the voltages coming from the power board WITH the YSUS plugged in (I'll have to do that tomorrow).
1) However, for the voltages I was testing coming from the power board, yes I was using DC voltage, and I was grounding them to the chassis when testing.
2) I was testing the Va and Vs voltages that were being listed.
3) For both Va and Vs from the connection between YSUS and power board, when turning on the TV, the voltages go directly to their listed values (54V and 210V), but they slowly go down to 0 over time with TV still on.
I don't know if further helps with diagnosis. Not really sure if there's a way to know if it is one or the other from this point.
If you would like to view my original posts on reddit, see this link:
http://www.reddit.com/r/AskElectronics/comments/16nnug/samsung_plasma_42_720p_model_pn42c450b1d_will_not/
So essentially, my issue is the YSUS Board or the powerboard. But I need a definitely way to test/known if it is one or the other before I go ordering parts. Really, I could order both parts but would like to only have to order one if I can.
(This post was edited by garsh on Jan 17, 2013, 2:32 AM)
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