Re: 19 polaroid tla-01911c
I did not see this symptom on my set. It does sound like the video signal is absent. Is the sound still working?
Dennis...
Dennis44
Member
Last Activity: 04-20-2010, 09:58 AM
Joined: 02-26-2009
Location: Tennessee
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Re: 19 polaroid tla-01911c
Thanks Bill,
If I can only find a 2.6 mm and the originals are 2.0 mm I wonder if it would cause problems to mismatch them?
If at some time a ccfl does go out I will measure the diameters more precisely and replace them all.
Dennis...Leave a comment:
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Re: 19 polaroid tla-01911c
Bill,
The tv has been working all this time. However it did start shutting down again.
I noticed the resistive loads I installed for the top ccfls had burned badly so they were causing an unbalance.
I went ahead and dismantled the lcd panel. I found a wire to the top set of ccfls had overheated and was completely open.
I cut the burned area away from the wire insulation and re-soldered it to the ccfl.
Now everything is back to normal. All feedback voltages are about 4.5 vac.
I did measure...Leave a comment:
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Re: 19 polaroid tla-01911c
[QUOTE=PlainBill]
Bill,
Thank you for your help. I have not had the time to spend on this tv lately.
Also, since it is working with only two lamps my incentive is not great.
I will eventually find out what lamps are in the set and let you know.
DennisRe: 19 polaroid tla-01911c
[QUOTE=PlainBill]
Bill,
Thank you for your help. I have not had the time to spend on this tv lately.
Also, since it is working with only two lamps my incentive is not great.
I will eventually find out what...Leave a comment:
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Re: 19 polaroid tla-01911c
[QUOTE=PlainBill]
Plain Bill,
I opened up the tv again today. It has been working for several weeks with the bottom ccfls connected and the upper driver having resistive loads.
I used the mod light driver on the suspected upper tv ccfls. It fired them or at least one ccfl. I did not open up the screen to see each ccfl. I noticed the mod light driver has both of its lamps in parallel so if one of the tv's ccfls were shorting it would have effected both. However a weak one would let the other one work. ( I powered the mod light...Leave a comment:
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Re: 19 polaroid tla-01911c
[QUOTE=PlainBill]
I have had this tv operating over a week now with only the two bottom ccfls connected and resistive loads on the top winding. So far I have had no problems.
It is amazing how well the set works with only the bottom lamps functioning.
I primarily am using it as a pc monitor.
I did order and receive the case mod lamps.
Before I take this tv apart again do you think the 12" ccfls will work in this 19" unit?
Thanks again,
DennisRe: 19 polaroid tla-01911c
...Leave a comment:
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Re: 19 polaroid tla-01911c
[QUOTE=PlainBill]
Ok I verified that the P on, B on and Bri logic levels are the same when the tv is ON as when the tv is On but the lamps are shut down.
I wired the series resistors up so I could measure the feedback voltages with the power on.
If I have the bottom ccfls on the bottom winding and use 450K resistive loads on the top windings I read about 5 volts ac each feedback on the bottom windings and about .160 vac each on the top. If I swap and but the bottom ccfls on the top winding and the resistors...Leave a comment:
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Re: 19 polaroid tla-01911c
[QUOTE=PlainBill]Yes, I have several. The question is 'Are the CCFLs shutting down because of either a fault with the CCFLs or the inverter; or are they shutting down because of a command from the TV controller?'
I have attached a marked up version of the power supply / inverter board. I would like to see the label next to connector I circled. Could you either take a clear picture, or transcribe it.
One thing to try would be driving the CCFLs using a different inverter - such as the one supplied with a case mod light kit....Last edited by Dennis44; 08-10-2009, 10:10 AM.Leave a comment:
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Re: 19 polaroid tla-01911c
PlaneBill
You are right from what I can tell. The ccfls are in series and the junction seems to be monitored. It almost seems like it keeps track of the differences before it shuts down. A am assuming this since I can swap leads or loads around and it will work for awhile before it shuts down again. Sometimes it will work for a few days.
As I mentioned to Krankshaft I will try to measure the feedback voltages with the ccfls and then resistive loads and look for differences. I am using 820k ohms. Any suggestions?
Thanks,...Leave a comment:
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Re: 19 polaroid tla-01911c
Thanks for the data sheet info. That helped to check out the inverters. They all looked good with my DVM on diode. all juctions were > 600 ohms.
This tv has two driver packs that drive two pair of ccfls in series. They are connected from one side of the secondary in series to the other side of the secondary. the point where the pair are connected in the middle is sent back to the board through some 2k resistors (4k total). I assume this is a current measuring provision.
It is difficult to measure voltages...Leave a comment:
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Re: 19 polaroid tla-01911c
Hi Krankshaft,
The numbers on the packs are 4511GD.
Maybe I can locate an o'scope to see how the signals look. Just looking at the input voltages with a dvm does not show any differences in the dc levels or the ac levels.
It almost seems like if I change the load I can make the set work for awhile.
I have added some 820k resisters in place of the lamps and the drivers seem to stay on although I have not left them on very long. I thought by only using two lamps I would reduce the load. This worked...Leave a comment:
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Re: 19 polaroid tla-01911c
FYI,
I am so sorry I have not gotten back on this forum to update the problem. Moving the wires around only solved the problem for awhile. Eventually the problem reoccurred.
The way this system is set up the four wires only go to 4 lamps. It really should not matter where they are plugged in from what I can tell.
I am waiting to see if I can get a service manual for this tv. That way I can make better judgments as to what is not normal as far as voltages etc.
DennisLeave a comment:
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Re: 19 polaroid tla-01911c
Well it seems to be working again. I was trying to test the currents in each of two ccfl that are in series. I identified that the two series pair currents did not match. When I swapped the lower connections with the upper connections it started working and has been for several hours. I may have not labeled the connectors correctly to start off with.
So it appears that replacing the capacitors did fix this set after all.Leave a comment:
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Re: 19 polaroid tla-01911c
Actually only the back light shuts down. The audio does stay up. At first I had the source to the tv set to PC and there was no audio anyway. If it does not sense a vga signal it shuts down. I was able to change it blindly to tv input.
I am not as familiar with LCDs. I will check for shorts etc to the CCFLs. Are there any ohmic values I should expect? I also need to read up on the basics of LCDs.
Thanks for you input.Leave a comment:
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Re: 19 polaroid tla-01911c
Not sure if anyone is still checking this thread. I did go ahead and replace 14 capacitors. I used Panasonic FC series. I have the same symptoms. Unit powers up for a few seconds then shuts off. You can see the "Polaroid" logo appear just before it shuts down. If I disconnect the four cables that I assume go to the panel lights it will stay on and the audio plays. I would appreciate any suggestions. Where can I get a service manual or just a schematic diagram?
DennisLeave a comment:
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Re: 19 polaroid tla-01911c
Hi I'm new here. Thanks for a neat forum. I grew up on Vacuum tubes so LCds are new.
I have the same tv with the same problem. None of the capacitors appear bad.
Mine has procon and hec capacitors.
If the set has been off for some time it will stay on longer but the screen does seem to be noisy. I was wondering if there are some basic voltage measurements/ripple I should look for. If a voltage is cut off, can any of the plugs going to the lcd be removed to see if problem goes away?
Thanks, DennisLeave a comment:
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