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25 Year Electronic Tech
25 Year Electronic Tech, Technician
Category: TV
Satisfied Customers: 894
Experience:  25+ Years Consumer Electronics Technician, Component Level, 10+ years Telecommunication Engineer
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Sharp LC-37D44U. The backlight will only stay on for one second,

Customer Question

Sharp LC-37D44U. The backlight will only stay on for one second, then out. I'm still able to make out images if I shine a light on it. Also tried updating software but it only re-starts without completing. Tried another inverter but the same exact result. Is the problem with power supply or CF lights? or ...
Submitted: 3 years ago.
Category: TV
Expert:  25 Year Electronic Tech replied 3 years ago.

25 Year Electronic T :

Hello, is the inverter board a new board and is it the exact replacement, your problem most likely would be either the inverter board or the power board. let me know. thank you

Customer :

The replacement inverter board was supposed to be a working pull from a new working TV with a cracked screen, through Ebay. It is a equivalent replacement. But if the problem is with the inverter, what's the chance of its symtom being identical with the original?

25 Year Electronic T :

Hello, probably not very likely, but possible. Just as likely would be the power board's supply voltage is bad.

Customer :

OK! Alright, I've guessed so much. So what do you suggest?

25 Year Electronic T :

For some reason the service manual I have access to does not show the power supply voltages that feed the inverter board, but if your are competent to do so you can measure and monitor the supply voltages to the inverter board, I think there are two or three. You might be able to see if one drops off or goes low. I spotted a couple of power supply boards, here are the links. hope this helps. let me know. Thank you http://greenchip.shopjimmy.com/catalog/product/view/id/196165/s/power-supply-lc-37sb24u-sharp/ ----- http://www.partstore.com/Part/Sharp/Sharp/LC37D44U/Sharp/Sharp/RDENCA272WJQZ/New.aspx

Customer :

With all respect, the reason I'm coming to you is so I won't shell out big bucks stabbing in the dark ... The power board has markings at the connection point with the inverter. There are about 4 ports marked 60V. One or 2 marked 13V. signals, etc. I'll provide the list tomorrow.

25 Year Electronic T :

I show there could be 12 volts also, but it might just be the 60 and 13, if you can monitor those two maybe you can determine something.

Customer :

Sorry, my last entry was somehow unrecorded. Here are the pictures for the connector: Inverter side: http://www.box.net/shared/z37cqxic3a (SGND, OFL, ERR, REG2, ADMIN, 13V, NC, GND, GND, NC, 60V, 60V) and Power board side: http://www.box.net/shared/tos1uhin9i (STB, OSC, REG BRT, NC, NC, GND, GND, NC, 60V, 60V).

25 Year Electronic T :

Have you monitored the 60 volts and the 13 volts to see if one drops off?

Customer :

Sorry, busy weekend. I just tested the voltage on both 60 & 13. There is no drop off, at least not in voltage. Should I test for amperage also? If so, what would be the norm or minimum amperage?

25 Year Electronic T :

Do you have any warranty on the inverter board you just installed, I would think that the power supply is functioning as it should.

Customer :

If it's not the power supply AND the two inverters behave exactly the same. That leaves the CF lamps themselves, right? What's the chance of them going bad all together?

25 Year Electronic T :

not very likely, I can't imagine both lamps going bad at once. was the inverter replacement inverter board a new unit, or was it pulled from a salvaged tv. I have gotten parts from shopjimmy.com that were bad, as they do pull parts from units that have broken screens or something like that, but you never know what you are going to get.

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