Author Topic: Toshiba TV backlight troubleshooting  (Read 1243 times)

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Offline eugenenineTopic starter

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Toshiba TV backlight troubleshooting
« on: July 13, 2016, 10:35:25 pm »
I am troubleshooting our old TV, a Toshiba 32hlc56 with no backlight.  I have replaced laptop backlight tubes before so when I found that I could see a dim image by shining a light on it I figured the same, a burned out bulb.  However I opened this and found 8 of them which told me I have a much greater chance of a power supply issue.   I did some searching and found a badcaps.net which says some tvs/monitors if one bulb burns out the inverter shuts down and they typically troubleshoot with a spare bulb. 
I don't have any spare bulbs so I'm wondering if I can troubleshoot in another way.
First does anyone have any info on these, what voltage should I see from the power supply to the backlight inverter board
second can anyone confirm this is the case with this model (or Toshiba's in general),will one lamp shut them all down?
 

Offline Kilrah

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Re: Toshiba TV backlight troubleshooting
« Reply #1 on: July 13, 2016, 10:48:11 pm »
Measuring the voltage on a CCFL backlight without an HV probe is not a very good idea, especially if something causes it to run without a load.

IMO shorting the tubes one after the other would be a wiser thing to do, hopefully can help you find the broken one.
 

Offline eugenenineTopic starter

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Re: Toshiba TV backlight troubleshooting
« Reply #2 on: July 13, 2016, 11:09:06 pm »
I was going to measure between the power supply and the hv inverter board, wanted to make sure I have low voltage power there first.

I didn't think about shorting one tube at a time, good idea, I'll try it.
 

Offline BMack

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Re: Toshiba TV backlight troubleshooting
« Reply #3 on: July 14, 2016, 07:28:23 am »
Power supply should output 24v to the inverter. If the voltage is not there or is low, disconnect the inverter and try again. If there is no voltage, the power supply is likely bad. If the inverter kills the 24v, it's either the inverter or the panel. If the voltage is low and fluctuating, it's the power supply.

You might also need to check back light on(bl_on) coming from the main board, should be 3.3v or 5v.
 


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