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Old 06-14-2012, 04:03 PM   #1
PTCS
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Default Question about Power Supply voltages

I have an Element FLX-3211B LCD TV that will not turn on. Before I received it, somebody installed a "cap kit" in the power supply. I was told that before the cap kit, it would often not turn on or sometimes even off when the power button was pressed. It eventually died completely. After the cap kit, the only signs of life are the standby indicator on the front of the TV turns from red to blue when the power button is pressed. On the power supply, the red LED flashes most of the time when "on".

In the "on" condition, the power supplies voltages are correct as marked on the board at the output connector with the exception of the 20v pin which is actually producing 24v.

I have checked for a "no backlight" condition and can not see any faint image.

My question is, is it normal/O.K. for the 20v pin to actually have 24 volts? If so, then is it safe to assume that the main board is defective?
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Last edited by PTCS; 06-14-2012 at 04:30 PM..
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Old 06-14-2012, 04:11 PM   #2
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Default Re: Question about Power Supply voltages

Please post the pictures of the boards using GO ADVANCED/FILE ATTACHMENT UPLOAD function.
Pictures will help troubleshooting.
I believe this is the same model ad POLAROID TV.
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Old 06-14-2012, 04:33 PM   #3
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Default Re: Question about Power Supply voltages

I have added a photo of the power supply and main boards to the original post. PS is the Proview design...part number IPOS 150, REV. 1.8
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Old 06-14-2012, 04:44 PM   #4
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Default Re: Question about Power Supply voltages

Yes same chassis as used in Polaroid FLX-3211, ELEMENT FLX-3210.
The 3210 had bad caps in the panel assembly:
http://s807.photobucket.com/albums/y...nt%20FLX-3210/
and bad caps in the power supply.
Take the reading of the 12v and the 5V also.
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Old 06-14-2012, 08:04 PM   #5
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Default Re: Question about Power Supply voltages

Thank you for your responses. As mentioned in my original post, I have verified all voltages as correct with the possible exception of the 20v pin that is measuring 24 volts. Your first reply gave me enough information to verify that 24v is also acceptable (searching the alternative product numbers).

Based on your second response, I pulled the backlight assembly and tested a random few of the backlight capacitors (out of circuit). They are the same 10pf 6kv as your referenced pictures, and are averaging about 132pf. However, I question the reliability of these results as these are 10pf caps with a 5% tolerance, and the lowest setting on my meter (Fluke 287) is 1.0 nf...10pf is 1/100 of this. This is a VERY VERY low reading for the range of my meter. I actually get random numbers in this range with the meter sitting idle (not connected to anything). For what it's worth, the caps are all in excellent physical condition (not like your pictured "bad" caps).

I suppose now that I have the unit dissembled this far, I should spend the $15 give or take and hope for the best?
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Old 06-14-2012, 08:59 PM   #6
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Default Re: Question about Power Supply voltages

Look for the caps with brown stain, it will be the sign of heat. 132pf reading does not sound right, use the Ohm meter to check the resistance also, they all should show open circuit.
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Old 06-14-2012, 10:42 PM   #7
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Default Re: Question about Power Supply voltages

Quote:
Originally Posted by PTCS View Post
This is a VERY VERY low reading for the range of my meter. I actually get random numbers in this range with the meter sitting idle (not connected to anything).
Maybe try using the relative function to zero out the readings and remeasure the cap again?

Some fluctuation is normal. My Fluke 187 (the predecessor to your 287) fluctates at around 0.087 nf while sitting idle.
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Old 06-16-2012, 02:00 PM   #8
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Default Re: Question about Power Supply voltages

Quote:
Originally Posted by budm View Post
Look for the caps with brown stain, it will be the sign of heat. 132pf reading does not sound right, use the Ohm meter to check the resistance also, they all should show open circuit.
The caps in this one all appear in perfect physical condition. Resistance wise, they all test as open circuit. Also, for what it's worth...all of my CCFL bulbs are nice and white (no discolored ends). The solder joints all look good as well.

Quote:
Originally Posted by retiredcaps View Post
Maybe try using the relative function to zero out the readings and remeasure the cap again?
An excellent idea...kinda reminds me of the old days with my old Simpson 260 on the ohms scale. In the relative mode, I am getting readings of about 10pf-20pf. Although possibly out of spec, probably fine?

I suppose at this point, I should go back to looking at the inverter side of the power supply. I have to admit, that even though I have read to test the inverter transformers, I have not yet done so. The backlight caps sounded too promising...especially since I had read that a bad backlight assembly can cause the flashing red light that I am experiencing on my power supply.
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Old 06-16-2012, 04:19 PM   #9
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Default Re: Question about Power Supply voltages

Hi - Does the power light stay on blue when it reaches its stable fault state.
Can the set be switched off using the power button.
When you first switch on do the back lights flash on at all - try in a darkened room.
Can we have pictures of the back of the power supply and main board and can you do
a sharp focussed picture of the main board without the glare.
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Old 06-16-2012, 05:49 PM   #10
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Default Re: Question about Power Supply voltages

Incorrect forum for my query.

Last edited by mmamuk; 06-16-2012 at 06:01 PM.. Reason: Incorrect forum for my question.
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Old 06-16-2012, 06:11 PM   #11
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Default Re: Question about Power Supply voltages

Post #10 and my response is now in the Hanns G megathread after OP realized the mistake.
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Old 06-16-2012, 07:15 PM   #12
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Default Re: Question about Power Supply voltages

Can you see all the lamps light up as I shown in my pictures?
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Old 06-16-2012, 10:42 PM   #13
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Default Re: Question about Power Supply voltages

No, no backlights at all.
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Old 06-17-2012, 12:45 AM   #14
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Default Re: Question about Power Supply voltages

That means the main inverter problem, the ballast caps are for for each lamps.
So we have to look further at the inverter circuits, this inverter driving voltage is not 24Vdc like the typical Inverter in most TV, this one uses 400Vdc for driving the two inverter transformer. Can you look and see if the two cap 10uF 450V caps (they are next to the two inverter transformers) are replaced?
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Old 06-17-2012, 05:27 AM   #15
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Default Re: Question about Power Supply voltages

Quote:
Originally Posted by selldoor View Post
Hi - Does the power light stay on blue when it reaches its stable fault state.
Can the set be switched off using the power button.
Can we have pictures of the back of the power supply and main board and can you do a sharp focussed picture of the main board without the glare.
Working on these?
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Old 06-17-2012, 11:08 AM   #16
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Default Re: Question about Power Supply voltages

I have not specifically tried to see how long the TV would stay on, but the TV has stayed on (blue light) as long as I have let it so far. Currently it does turn off when the power button is pressed. I think at this point, it is safe to reassemble the LCD panel and then I can specifically test this further.

Please note from my original post, that I received the TV after a cap kit had been installed, and was told that before the cap kit the TV would often NOT turn off when told to (but it still had a picture at that point).

Quote:
Originally Posted by budm View Post
Can you look and see if the two cap 10uF 450V caps (they are next to the two inverter transformers) are replaced?
Yes, the two 10uF 450v caps near the inverter transformers were replaced as part of the kit. I am not certain, but I believe the kit was purchased from this site (he had referenced this site when passing the project on to me). It consisted of 10 to maybe 15 capacitors. I have verified that the capacitors were installed correctly (good solder joints and correct polarity).
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File Type: jpg psback.JPG (1.64 MB, 14 views)
File Type: jpg mainboardback.JPG (1.97 MB, 17 views)
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Old 06-17-2012, 12:24 PM   #17
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Default Re: Question about Power Supply voltages

Great picture thanks - wish i could spot something wrong. I have marked a picture with what I thing are the secondary windings although as there was no flash at all I doubt if they are the problem. To Check (Power off)Meter on Ohms 2000 measure S1>S2 and S2> S3 and post results. Whilst looking for these I notice some grey solder joints. May just be the pic but one at least looks a bit odd - perhaps you could reflow them and check continuity with trace.
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Old 06-22-2012, 06:29 PM   #18
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Default Re: Question about Power Supply voltages

Quote:
Originally Posted by selldoor View Post
Great picture thanks - wish i could spot something wrong. I have marked a picture with what I thing are the secondary windings although as there was no flash at all I doubt if they are the problem. To Check (Power off)Meter on Ohms 2000 measure S1>S2 and S2> S3 and post results. Whilst looking for these I notice some grey solder joints. May just be the pic but one at least looks a bit odd - perhaps you could reflow them and check continuity with trace.
Thank you for your help. The readings from what you have marked as S1>S2 is 36.46 Ohms, and S2>S3 is 37.34 Ohms. S3>S4 is also similar at 37.13 Ohms.

Good eye on the joints...The upper one you marked is a little grey, but does have continuity. The lower two are one of the capacitors that was changed before I got the TV.

While getting the readings you suggested, I did stumble on a 0 ohm resistor that was open (JR8). Since these are simply used as jumpers, I have soldered in a temporary wire to test with. Unfortunately, due to space limitations, I am not able to test the TV right now. I will post back whether or not this made a difference once I can test it.
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Old 06-23-2012, 06:53 AM   #19
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Default Re: Question about Power Supply voltages

Quote:
Originally Posted by PTCS View Post
Thank you for your help. The readings from what you have marked as S1>S2 is 36.46 Ohms, and S2>S3 is 37.34 Ohms. S3>S4 is also similar at 37.13 Ohms.
.
Drat, I keep doing that - I did mean S1 to S2 and S3 to S4 but they readings should
be in the hundreds at least, can you check perhaps 364.6 and 373.1
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Old 06-23-2012, 11:53 AM   #20
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Default Re: Question about Power Supply voltages

I double checked the transformers. Both are 36 ohms (in circuit). Is this test usually done in circuit?

I still haven't had a chance to test the unit after "repairing" the open circuit 0 ohm resistor yet...too many projects at the same time right now. Hopefully I can clear some room on the bench before this weekend is over.
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