Poloroid TDA -03211C- - - -Power Board IPOS 150 Ver. 1.8

[waitery]

Hi all,

I am having a problem with my Poloroid TDA - 03211C with Power Board IPOS 150 Ver. 1.8. I get a red led on the front, but it doesn't power on. Upon taking off the back to get voltages, I noticed that the caps at EC17 and EC 18 were blown. I ordered new caps from Digakey and also order new FET's at Q16 and Q17 and replaced all of them. I replaced the filter cap too with a new high temp Panasonic. After getting everythig back together, here are the voltages that I have from the pins....just nothing is powering on:

STB= 4.83
5STB= 5.13
5V=5.13
12V=11.78
20V= 23.98v

Also, the filter cap, when the main board and inverter is attached to the power board, it swells to 400V and holds steady on the reading. When I disconnect everything except the power, the filter caps is steady at 167volts. I have attached some pics. Any ideas or questions to help me along would be welcome!!

[waitery]

I forgot to add, the fuses are good on the power board as well.

[retiredcaps]

Originally Posted by waitery

After getting everythig back together, here are the voltages that I have from the pins....just nothing is powering on:

STB= 4.83
5STB= 5.13
5V=5.13
12V=11.78
20V= 23.98v

Also, the filter cap, when the main board and inverter is attached to the power board, it swells to 400V and holds steady on the reading. When I disconnect everything except the power, the filter caps is steady at 167volts.

All your voltages look good. Is the standby light on?

The 400V is due to the Power Factor Correction. I'm not an expert on this and still learning this portion, but I believe 400V DC is a correct reading. 167V DC is right for the big main cap when power is off, but not disconnected from the mains.

[cadillacman]

Hey make sure its not workingbut with no backlight. If you use a flashlight you can see if the lcd is working...

the only reason i say that is that i ran into a polaroid recently that had bad ccfls, it would powrer on then appear to lose video.. but was not losing video, was just losing the backlight.

[waitery]

Yes, the standby light is lit on the front. It is glowing red, but when I push the button, it doesn't turn on. No backlights, no relay hiccups, no nothing. There is also a red led on the power board located in the lower left corner that isn't illuminated. You can see it in my attached pics.

[waitery]

Forgot to add this in the post, but I am wondering if the board isn't hitting a threshold voltage, i.e. above 5 volts and above 12 volts, therefore it is sensing that it is under and shutting down. Any thoughts on that?

[PlainBill]

Originally Posted by waitery

Hi all,

I am having a problem with my Poloroid TDA - 03211C with Power Board IPOS 150 Ver. 1.8. I get a red led on the front, but it doesn't power on. Upon taking off the back to get voltages, I noticed that the caps at EC17 and EC 18 were blown. I ordered new caps from Digakey and also order new FET's at Q16 and Q17 and replaced all of them. I replaced the filter cap too with a new high temp Panasonic. After getting everythig back together, here are the voltages that I have from the pins....just nothing is powering on:

STB= 4.83
5STB= 5.13
5V=5.13
12V=11.78
20V= 23.98v

Also, the filter cap, when the main board and inverter is attached to the power board, it swells to 400V and holds steady on the reading. When I disconnect everything except the power, the filter caps is steady at 167volts. I have attached some pics. Any ideas or questions to help me along would be welcome!!

It's working. All of the readings you report show the power supply is working, the PFC is functioning properly, and the outputs are reasonable.

It's time to look at the main board. There are no relays on this power supply to make noise. I'm not sure about the LED, there is no indication of what it indicates.

PlainBill

[waitery]

I just bought a main board and installed it today. After the install, it has the same issue as the one I removed.

[waitery]

Does anyone have any other experiences or insights that they can share on this one? It seems strange that with two different main boards that I am having the same symptoms.

[hijodalgo]

does the red light changes to blue when you press power? if not,there could be a main board problem,but you said that you've changed.It's the same number?I,have found problems in the audio output,and that causes the tv to shutdown.. you can check this ---->http://blog.coppelltvrepair.com/sear...max-results=28
Hope this help..

[waitery]

No, it always stays red. I try the I/0 main control and also the remote and no dice....it will not go blue. It was a used main board that I purchased online, but it has a 30 day warranty, so I will be sending it back. Thanks for the link, I will check it out.

[ryankam]

I have the same TV with the same issue. These TV's are notorious for bad main boards (not power supply, but tuner board). Ordering these from Shopjimmy.com or discountmerchant.com can be frustrating because they say they test the boards that they can but how do they test. Shopjimmy has over 100 test tv's but there are 1000's of boards so not all get tested. And they usually get these from cracked screen units. So it is a tough gamble guying from these tear down distributors. You will think you have a problem solved, get a "new" part and that "new" part as the same issue, so you buy a million other parts and it turns out it was just a faulty main board the first time and the time you ordered a "new" one. so spend the extra $$. Verify the tv works with a "good" part. If so order a cheaper one and send back expensive one. Just so you are 100% sure of the problem.

[Dgtech]

I had one of these and all I found the problem to be in my case was a diode. Here is my post.

http://www.badcaps.net/forum/showthread.php?t=12886

It beat buying a new board at about $80. The diode was only $3.

[nfiniti9]

I have one of these tv's with the same issues. The previous owner tried replacing the caps but it did not fix it. I found the F2 fuse was bad. Does it matter if I replace it with a 5x20 (radio shack) and add my own pigtails? I am going to replace the transistors and plan on ordering the correct fuse as well but would like to get it going to make sure it works before I do. So would those larger fuses cause any issues? They are 3.15A 250v slow-blow. A veteran mentioned they were time-delay which i believe is the same?

[Dgtech]

The larger fuses (in size) should not cause any problem. I would not change the amperage any though. I'd put in a fast blow with the same amperage fuse. I dont recall what the amperage was on the original fuse though. I do remember this fuse is in the center of the board near a transformer. It's not too crowded there. It can be done with caution.

What was wrong with the transistor that you're changing? Which one is it?

[nfiniti9]

Nothing is wrong but they are 1.20 a piece so why not change them since they are known to be an issue on these psu. The fuse are the same amps, voltage and delay just bigger. There is definitely room in there.

[nfiniti9]

Works great. Thanks for the help.

[Dgtech]

I have one of these sets now.

Here's what I had originally:

Unit was not comming out of standby at all. No backlights.

Found bad caps for backlight circuit (2 X 10uF @ 450V) replaced with Rubycons.

Checked all remaining caps on secondary of power supply, all within tolerance. Changed a few that were a little low for my liking.

Here's what I got now:
Unit now powers up but goes out right away until unit is warmed up, then it will stay on for a while. I got the unit on right now and I'll leave it on overnight. I hope it will die completely so I can find the problem easier.

Standby voltage = 5vdc both when backlight is on as well as off - so it's not going into standby. Even the stanby LED does not change when unit backlights fail.

I checked solder joints on the transformers that feed the backlights.

I havent used the flashlight to check image yet only because - i got to find my damn flashlight... moving sucks!!!

I will post more info tomorrow as well as pictures.

[Dgtech]

Well, I left this unit on all night long and it stayed on. I shut it down and now it wont start back up at all. This is good. This is what I wanted. It wasn't broke enough before.

Originally Posted by waitery

STB= 4.83
5STB= 5.13
5V=5.13
12V=11.78
20V= 23.98v

In comparison to the poster above, my voltage read:

.................. OFF ...........................ON (FAILED STATE-NO BACKLIGHTS)
STB .............. 0 ............................4.68
5VSB.............. 5............................. 5
5V .................0 ............................. 5
12V ...............0..............................12
20V............... 0...............................25


By the way, I have no red LED on the power supply board. You'll find this in the bottom left hand corner of the power supply board pic above. Another clue is that no pins of the PWM chip (IC8) have any voltages on it (nothing significant). NO VCC VOLTAGE

[Dgtech]

OK.... an update to this...

After this was sitting for a while I got to power this set up and it still comes up intermittently. I had 12V on pin 13 of IC8 the PWM chip UNTIL the set went out and the LED (D13) came on. This LED has to be some kind of clue. This LED (bottom left hand corner of power supply board) stays off when the unit is working then comes on when the unit fails???