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Old 07-12-2020, 01:59 PM   #1
petehall347
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Default 40/233f bush tv powers on no backlight

just got this in for repair .i suspect its the led,s . checked power at the 2 backlight connectors .one goes to about 130v then drops to 50v .the other stays at 0v . when i swap backlight plugs over the 130v/50v swaps sides and also the 0v .
there is no flash . i was told the sound was out too .
barring stripping the panel to test the led.s is there any other testing to do apart from buying a backlight tester ?
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Old 07-12-2020, 05:01 PM   #2
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Default Re: 40/233f bush tv powers on no backlight

now looking at testers on that ebay and all the sellers appear to mostly same seller using different id.s ..its putting me off buying one there ..anyone have experience with ebay ones ?

just looking at this one ..https://uk.rs-online.com/web/p/led-d...7442/?sra=pmpn
no read out though so would have to add meters ..

Last edited by petehall347; 07-12-2020 at 05:06 PM..
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Old 07-12-2020, 05:45 PM   #3
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Default Re: 40/233f bush tv powers on no backlight

1) Can we see god clear pictures of what we are dealing with?
2) It sounds like you have open circuit in the LED string, you have Voltage feeding the Anode of the LED string but you get 0V on the Cathode return of the LED string.
3) The LED driver board is useless for testing the LED string, it use 5V USB power source and no boost converter. You need tester that can go up to 300V, the newer version of the LED tester can also drive the LED at much higher current than 30mA.
4) Which LED tester on EBAY that you see?
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Old 07-12-2020, 05:48 PM   #4
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Default Re: 40/233f bush tv powers on no backlight

Quote:
Originally Posted by budm View Post
1)
4) Which LED tester on EBAY that you see?
https://www.ebay.co.uk/itm/0-300V-Ou...UAAOSwmsxe8cqU
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Old 07-12-2020, 05:51 PM   #5
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Default Re: 40/233f bush tv powers on no backlight

looks pretty clear to me the board is working . just need to confirm with a good tester first before i attack the panel . i have a bad habit of fixing what isnt broken and breaking it .
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Old 07-12-2020, 06:54 PM   #6
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Default Re: 40/233f bush tv powers on no backlight

I bought SID GJ2C years ago.
https://www.ebay.com/itm/LED-LCD-TV-.../373088668062?

This new one claim higher drive current, not sure how true that is.
https://www.ebay.com/itm/SFDER-0-300.../163748769335?
https://www.ebay.com/itm/LED-Tester-.../273101005355?

Last edited by budm; 07-12-2020 at 06:57 PM..
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Old 07-13-2020, 12:22 PM   #7
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Default Re: 40/233f bush tv powers on no backlight

ordered one i posted before .
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Old 07-13-2020, 12:26 PM   #8
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Default Re: 40/233f bush tv powers on no backlight

Which one did you order?
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Old 07-13-2020, 01:02 PM   #9
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Default Re: 40/233f bush tv powers on no backlight

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Originally Posted by dick_barton View Post
Which one did you order?
https://www.ebay.co.uk/itm/0-300V-Ou...72.m2749.l2649
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Old 07-13-2020, 01:55 PM   #10
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Default Re: 40/233f bush tv powers on no backlight

Im just getting back into tv repair this is the meter i was thinking of getting https://www.ebay.co.uk/itm/0-300V-Ul...y/272579531904
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Old 07-13-2020, 01:58 PM   #11
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Default Re: 40/233f bush tv powers on no backlight

i didnt see one with current as well as volts
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Old 07-13-2020, 05:21 PM   #12
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Default Re: 40/233f bush tv powers on no backlight

Quote:
Originally Posted by vinceroger69 View Post
Im just getting back into tv repair this is the meter i was thinking of getting https://www.ebay.co.uk/itm/0-300V-Ul...y/272579531904
Hi Vince, Please let us know how high of the current this meter can put out at high LED Voltage level when you test it out, thanks.
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Old 07-14-2020, 01:55 AM   #13
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Default Re: 40/233f bush tv powers on no backlight

Quote:
Originally Posted by budm View Post
Hi Vince, Please let us know how high of the current this meter can put out at high LED Voltage level when you test it out, thanks.
yes i will do
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Old 07-20-2020, 08:44 AM   #14
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Default Re: 40/233f bush tv powers on no backlight

tester turned up today . tested led.s and they lit up from each plug .one is 3v ish different suggesting an led might have gone short .i can test again for exact figures ...strange thing is though i plugged the wires back in and the back-lights are now working .
i looked for a back-light setting and could only find brightness which i dont think affects back-lights so the setting might be done in service mode ?
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Old 07-20-2020, 09:46 AM   #15
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Default Re: 40/233f bush tv powers on no backlight

i dont get it ..both plugs now measure 60v with tv working them ... and both 53v running off the tester . all seems fine . am going to run it a few hours and see what happens ...
looks to me like the tester fixed them somehow ...
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Old 07-20-2020, 06:25 PM   #16
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Default Re: 40/233f bush tv powers on no backlight

May be bad connectors between the strips.
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Old 07-20-2020, 06:42 PM   #17
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Default Re: 40/233f bush tv powers on no backlight

Quote:
Originally Posted by budm View Post
May be bad connectors between the strips.
that did cross my mind . what i have done is left in in standby overnight .am going to run it a few hours tomorrow then put all the screws back then run it again a couple of hours .if still ok give back to the owner and see what happens . right now i cant fix it because it isnt broken .
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Old 08-13-2020, 05:46 PM   #18
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Default Re: 40/233f bush tv powers on no backlight

well its still working for the owner
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