got one of these from a friend who was gonna toss. it powers on fine led is blue stays blue screen lights up for 2 seconds with "PRIMA" on screen then gets kinda like a fuzzy screen you would get after a station goes off air then it goes black. led blue light stays on till i hit power button then goes red. none of the caps on board are bulged/leaking. nothing looks burnt/broken. i will post pic shortly.
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Re: Prima 21 inch lcd powers on then goes dark
10 minute expiration so im just replying with pic...........Attached Files -
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Re: Prima 21 inch lcd TV powers on then goes dark
a little update here... Prima 21 inch lcd TV model #LC-20Y15
hooked it up to dvd player and was able to get a picture with sound for 1 - 3 seconds then goes black. sound stays until i power lcd off. repeats same cycle when i power lcd back on...Comment
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Re: Prima 21 inch lcd powers on then goes dark
I misinterpreted some information the first time I read this. This sounds like the classic 'two seconds to black' issue. Possible suspects are inverter, backlights, or wires from inverter to backlights.
Note the cable from the power supply to the inverter. It appears there is information obscured by the cable. What does it say? Also, on the inverter, what is the part number of the large IC in the center.
If you look at the left connector on the inverter, you can see there are two connectors, one 5 pin, one two pin From the top down the wires are large gray, large blue, small black, small dark blue, large white, small white. The same arrangement is on the right side, but in reverse order.
The large wires are the drive lines to the CCFLs, they have a heavier insulation. The smaller wires are the return lines. While the backlights are working measure the AC voltage from each return line to ground. We are looking for one that has a different reading.
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: Prima 21 inch lcd powers on then goes dark
i hope i measured properly, im not advanced in the ac measure department.Originally posted by PlainBill
as u asked/requested
as pictured from left to right power in black and white cord side
s black .005 s white 2.20
s blue .005 s blue .005
s white 2.5 s black 2.35
please advise. thanks.Comment
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Re: Prima 21 inch lcd powers on then goes dark
OK, you are WAY ahead of me. I was working up to this gradually. Those voltage seem to indicate half the CCFLs aren't working. We're going to have to approach this differently.Originally posted by starmaxpc
I've located the datasheet, The pins of interest are 4, 65, 26, 27.
Set the meter to the 20VDC scale, connect the black lead to ground, plug the monitor into power and go through the following sequence for each pin.
Touch the red lead to the pin under test. Press the power button until the backlights come on. Note the voltage. Press the power button twice, note the voltage again. Go on to the next pin.
Hopefully both readings will be the same for each pin. For enlightenment, the BIT3106A inverter controller has two sets of pins to sense output voltage and current for the CCFLs.
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: Prima 21 inch lcd powers on then goes dark
Originally posted by PlainBill
i assume 65 was a typo and u meant 25 am i correct, if so then....
4 1.92
25 5.6
26 5.7
27 5.4
and i did a little pic edit to confirm. please advise.Attached FilesComment
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Re: Prima 21 inch lcd powers on then goes dark
You were half right. 65 was a typo. I meant pins 4, 5, 26, 27.Originally posted by starmaxpc
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: Prima 21 inch lcd powers on then goes dark
Originally posted by PlainBill
update on #5 pin
4 1.92
5 9.5
26 5.7
27 5.4Comment
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Re: Prima 21 inch lcd powers on then goes dark
ok i do not know what happened here was it just good luck or testing the right pin out??? its working?? after a couple of pin tests on #5 as u described i decided to stand the tv on end and i noticed the "VIDEO NO INPUT SIGNAL" nice and bright on the screen. i popped in a movie and watched for a few minutes. no problems. now... im gonna test for a few hours/days but any idea what happened here??Attached FilesComment
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Re: Prima 21 inch lcd powers on then goes dark
A lead from the inverter to a CCFL is shifting and either disconnecting from the CCFL or shorting to the panel. When you stood it on end the wire shifted so the problem no longer existed. I thought those leads to the CCFLs would be prone to abrasion. Or it could be any similar problem of a bad solder joint.Originally posted by starmaxpc
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: Prima 21 inch lcd powers on then goes dark
ok this has been working for a good while now and what i found was when i looked real close at the inverter board area was when i did a reflow of the some solder i accidently fused #4 and #5 pin on the IC chip and thats when it started to work and now it is currently working with no problems. is that a good thing or not? you mentioned the ccfl's? are those pins on the IC chip firing the power to those ccfl's or did my solder mistake make things work? i am now into a movie here approx 30 minutes with no problems? please advise....Originally posted by PlainBillComment
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Re: Prima 21 inch lcd powers on then goes dark
I think that disables the protection circuitry for one side of the inverter. NOT something you want to leave in place.Originally posted by starmaxpc
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: Prima 21 inch lcd powers on then goes dark
well i was able to clean the joint made between #4 and #5 pin. any other suggestions here? its back to the beginning with power/lights for a couple seconds then dark screen with an image in the back ground? thanks.Comment
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Re: Prima 21 inch lcd powers on then goes dark
thought id post a pic on inverter if it helps any...Attached FilesComment
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Re: Prima 21 inch lcd powers on then goes dark
I've marked up the picture. Red circles are the output of one inverter transformer. Compare the resistance of the outputs of all six transformers.Originally posted by starmaxpc
Blue circles are the drive to the transformers. Compare right side to left side.
Black circle - pair of fuses. Check if they are good (very low resistance).
Yellow circle. Make sure both caps are soldered in place.
PlainBillAttached FilesFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: Prima 21 inch lcd powers on then goes dark
Hope this helps...Originally posted by PlainBillComment
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Re: Prima 21 inch lcd powers on then goes dark
Starmaxpc, so did you ever get it fixed? Details?Comment
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Re: Prima 21 inch lcd powers on then goes dark
no from what help i've received here it seems to me the inverter is toast. i'm not really sure where and if i can get parts for it. really too bad as it is in really good condition. do you have something similar??Comment
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Re: Prima 21 inch lcd powers on then goes dark
Google around and you will find a source for LCD parts. Some transformers are available individually, without the rest of the board. You may be lucky.
You can also attempt to find the 'part number' that is likely printed on the board. Try 'em all, it can't hurt...
I am assuming that you compared the ohm readings on the transformers and found them to be different. Are they all bad? If you use a DMM, you should find that the windings are low ohms end to end -- and high ohms from one set of windings to the other.
The output winding would have a low resistance and the driving winding would have a low resistance, but cross-checking from input to output should have a high resistance.
tomComment
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