Sharp Aquos LC52SE94U hit by surge

[Fwrothy]

So don't know why it wasn't in the suppressor but what's done is done.
Here's what I know: during a recent ( February??) thunder storm the power fluctuated and the tv went down. Since the power eventually went out the tv spent the night unplugged but of course would not power up after that.
Upon inspection the fuse had blown. After unsuccessfully trying to local source a replacement T6.3AH250V ceramic replacement I stuck in a glass 4A I had which blew immediately upon plugging in. Got really brave after awhile and going against all better judgement used an 8A, which also lasted a fraction of a second...
I have done my research and come up with this hypothesis, ruling out the line filter( can I?) where the fuse is mounted It must be a fault in the psu board. That board is an RDENCA235JQZ I believe, which seem to be scarce at the moment(shopjimmy and many other sites r out of stock) which is to me a good indicator of a common problem.

My questions are mainly:
Strictly for the purpose of ruling it out, can the line filter (RUNTK317WJQZ) be tested in a 'static state'- disconnected from the psu board? I'm assuming it won't blow the fuse when there is no output load. What would be an acceptable output range? I'm assuming ~120vac
Are the PSUs sold by online vendors new or harvested/reconditioned?
Is it realistic to try to fix my board (as I understand it the problem is most likely a fried diode/rectifier)? If so can someone help be to start down the path to the troubleshoot?
The replacement fuse I spec'd since most readily available in my area would be an Eaton/Bussman: S505 series TD, high breaking capacity. Can anyone confirm deny?

Any help on these matters would be greatly appreciated(-:

[tonyuk]

Re: Sharp Aquos LC52SE94U hit by surge

could you post up pics for people to help you with does sound like a psu fault

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

@tonyuk Thanks for the reply. I'm new to this so I get some pictures up asap- a soon as I figure out how...

[tonyuk]

Re: Sharp Aquos LC52SE94U hit by surge

@tonyuk Thanks for the reply. I'm new to this so I get some pictures up asap- a soon as I figure out how...

if you get pics onto laptop when you reply to thread theres a paper clip clicked on that then upload

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

iPad still getting the hang...making progress I think
Can only seem to upload one pic for now hope it's somehow helpfu.btw I have thoroughly scanned for damage can't seem any although haven't removed psu board to look at trace side.

[tonyuk]

Re: Sharp Aquos LC52SE94U hit by surge

i would try get pics zoom in more on the psu im new to this aswell but i would remove psu and look at back of it also post close up pic of both sides then test board while out with a meter while your waiting for more info from the other guys

[budm]

Re: Sharp Aquos LC52SE94U hit by surge

OK, test the AC FILTER INPUT board by itself, no power to it, nothing connected to it.
Check the resistance reading at the two legs of each MOV.
Check the resistance reading at the two legs of each Gas discharge protection devices.
Check the resistance reading at the two legs of each of those X/Y safety caps.
Make sure to report the reading if they are in OHM, K OHM, M OHM.

[Noobomatic]

Re: Sharp Aquos LC52SE94U hit by surge

i recently had a surge affected set i didnt have a replacement for the surge absorber (znr) maybe check that for a short or osmething i would be following up the psu from the 240v connections and having a play with the multimeter if you have one and you should never put a higher rating fuse while testing, you could do more damage than good.

either way i would check bridge rectifiers, they normaly have ~+~- printed on them check them for shorts ..etc the parts would mostlikely need to come out of the board if there is a short in the board, i had to replace a "ZNR" black capacitor looking thing (panasonic surge absorber) and a bridge rectifier (litle rectangle thing about the size of a pinky fingernail) hope that helps a little

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

budm-thanks for the reply. The 2 smaller gdpd read .2 ohm everything else is OL.
Using a fluke 83...
Thanks noobomatic, gonna try and work my way up that tree.

[budm]

Re: Sharp Aquos LC52SE94U hit by surge

Lift one leg of those GDPD off the board and take the resistance readings on their legs again, if they read 0.2 Ohms then that is the problem. The TV will still function without the protection devices in place.
If you measure the resistance on the two prong of the AC inlet pin, it should show high resistance.

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

I'm sorry budm made a mistake, took the board off chassis to desolder and discovered the mov z7000 to have a 1.475Mohm value.

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

[QUOTE=Fwrothy;424311]I'm sorry budm made a mistake, took the board off chassis to desolder and discovered the mov z7000 to have a 1.475Mohm value.

[tom66]

Re: Sharp Aquos LC52SE94U hit by surge

Looks like a similar power board to one I have - let me know if you need comparative measurements.

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

@tom66 thanks, the mov with the 1.475M read is a tvr14681, designated as z7000 on the trace side. I have .2-3ohm across the gas discharge tubes labelled SG7000 and 7001 respectively that are in parallel with the toroidal coils.
Would appreciate those 3 comparisons.
As I understand it, there isn't really a definitive static test for MOVs, so would capacitance be any better? If so that tvr14681 reads .61F

[budm]

Re: Sharp Aquos LC52SE94U hit by surge

So what resistance do you get at the AC input jack reading between L and N? MOV will usually shorted out (scarified itself and caused the main fuse to blow). If it shows very high resistance (in 1000 of Ohms), then you should be able to power up this board by itself without blowing the fuse, or you can use a 75W lamp connected in place of the fuse, the lamp should not come on and stay on bright.

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

It's the same said 1.475Mohm. Which makes sense to me looking at the trace. I like the lamp idea, thanks! So far it's looking like with that kind of resistance this board should check out and I will have learned valuable troubleshooting skills. Onward(-:

[budm]

Re: Sharp Aquos LC52SE94U hit by surge

With the fuse in place? If that is the case, that board no longer has the shorts in it, next one will be the main power supply board.

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

Yes fuse in, 1.475M at input pins. Plugged in now, disconnected from psu. ~ 120vac at output.

So now for the psu board...

[tom66]

Re: Sharp Aquos LC52SE94U hit by surge

I can get the readings you need but first I need to move some things out of the way.
If you need, I believe a schematic for the PSU is available in the service manual for a similar model, the LC-52XL2E, which is the one I'm working on.
http://www.tgohome.com/ServiceManual...&Search=Submit

[Fwrothy]

Re: Sharp Aquos LC52SE94U hit by surge

Thanks, that's a great reference but unfortunately it looks like that model has a RDENCA231WJQZ board-my board is an RDENCA235WJQZ- similar but I doubt the same. I will keep looking around, thanks again!

I have the board out inspected trace for any obvious damage- nothing (some large areas show a slight discolouration not sure if the pic shows...)

Since I can't power up not sure on the next step...

Btw is that a European model and thus different designation; everything looks spot on.