Polaroid TDA-03211c IPOS150 Power Supply Problem

[Firebirds71]

I have a polaroid TDA-03211c LCD TV with an IPOS 150 REV. 1.8 Power Supply board, the LCD is black, the power turns on but I have no backlight, I have replaced the capcitors on the power board with the exception of one, the big filter cap which I have just noticed is domed pretty good. The LED in the lower left corner of the board is flashing when the power is turned on and stays off when the power is off. Anyone have any ideas?

[Dgtech]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

Post pictures whenever you get a chance. Use Manage Attachments when posting pics.

[ryan74]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

I have a problem with ipos 150 rev 1.8 for my polaroid 26in. I have no power at all, no voltage at standby. When I got it it went into standby. When i powered on the blu light came on for a sec and it shutdown. so i replaced 2 large caps, 2 transistors, and a fuse. after that i decided to check the diode(D10) tested ok so i put it back in. i got everything back together and plugged it in and no front led. a part at loc (Z6) ticks and flashes. also, did i get the diode installed in the right direction. this tv had the dvd removed. It should still work as a tv without it right? theres just a hole where it was.

[Dgtech]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

I tried to find a picture of when I had done the repair on a similar tv to show the correct polarity of D10. If installed correctly, I think you should get about 24Vdc on the tab. I cant remember exactly.

As for the flashing part, no parts should be flashing.

Did you check the capacitors undereath the heatsinks?

[Dgtech]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

Check here for more info on these power supplies. Note - Post 15 will verify the correct polarity of D10.

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

[ryan74]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

Diode seems to be installed correctly.
I will check the caps under heatsink.
If I understand right I should get a voltage reading off the top of diode where it soldered to heatsink?
Can u identify the part I said was flashing? I have no clue what it is but I might be able to get a part number off it. It looks glass with a rusty color. Tracing backwards from 5vsb to the part that flickers, to capacitors, to diode.

[Dgtech]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

That looks like some type of zenor diode. I've never seen them flash before. That's a new one to me.

I'm not sure what the voltage was off of the heatsink of the diode but I know one is there. I think it might have been about 24VDC.

[ryan74]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

It is a zener diode. I guess it doesn't flash, more like a tiny spark inside

I'm pretty sure your right about 24vdc from diode, I think I saw that somewhere else

I'll check back in a few days when I have a chance to test more.

Thanks for the help and quik response so far.

[tom66]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

If it is flashing, the zener is shorted out, and you are seeing the silicon glow red hot, screaming for mercy .

I suggest you try to figure out what circuit it is on. More than likely, it's some kind of protection for a voltage rail, so you can find a zener with a similar voltage rating (plus a few volts) as the rail it is on.

[ben7]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

If it is flashing, the zener is shorted out, and you are seeing the silicon glow red hot, screaming for mercy .

I suggest you try to figure out what circuit it is on. More than likely, it's some kind of protection for a voltage rail, so you can find a zener with a similar voltage rating (plus a few volts) as the rail it is on.

Also, replace the secondary capacitors, if they go bad, sometimes the power rail will get noisy, and the voltage spikes might have killed this zener.

[budm]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

ZD6 is a Zener 6.2V Zener diode, it is connected across the 5BSV output and Ground (Anode to Ground, Cathode to 5VSB pin) to clamp it down incase the 5V goes higher than 6.2V.
And Yes, you should have 24VDC on the heat sink of D10, Cathode is pointed up.
http://s807.photobucket.com/albums/y...%20TDA-03211C/

[ryan74]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

D10 diode tested 18.5-22v. It seemed to spike at the same time the zener diode sparked. I get .185v at the 5vsb con

I went ahead and ordered the whole cage for $40 but I really want to learn about these tv's and fix this board.

I figure I'll replace d10 diode, caps under heatsink, and zener diode but I'm conserned about the voltage going into d10 diode

On the bottom of the board there is a tiny part between 2 capacitor leads. (This cap is under heat sink) should I test this and how? If u need a pic I'll get one.

[budm]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

It sounds like you 5V is higher than 6.2V Zener diode is try to clamp down, it is shorted out.

[ryan74]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

I tested capacitors and transistors out of circuit with multimeter but I'm not sure what acceptable ranges are. Transistors tested .13v and .16v on other.
Tested D10 Diode at .42
Caps tested:
220uf 25v tested 225uf
220uf 25v tested 214uf
220uf 25v tested 220uf
100uf 35v tested 102uf
100uf 35v tested 97uf
1000uf 10v tested 1021uf
1000uf 10v tested 1009uf
1000uf 10v tested 1037uf
470uf 35v tested 462uf
Zener diode tested 0v
I hope this helps, I'm a novice but I'm wondering if zener diode is all that is bad.
If I tested wrong please correct me

[budm]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

Can you remove that Zener from the board and use OHM mode (if the diode is shorted out, it will not be reading like diode any more, more likely to be really low Ohm in both directions).

"Transistors tested .13v and .16v" Not sure what you mean from the reading since it has 3 legs.

[ryan74]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

Zener diode is bad 0.0 ohms (0.0v in diode test mode)

With meter in diode mode and ground lead on center leg of transistor I get .13v on each of the other 2legs. With pos lead on center leg I get .OL on the other 2

In ohm mode testing with ground lead to center leg I get .63kohms on the 2 other legs. With pos lead on center leg the other 2 legs test .OL - 13kohms it bounces back and forth

Hope this helps

Are caps within range.

All my tests are with multimeter but I don't fully understand how it all works. I just follow basic directions for testing resistance, capacitance, continuity and so forth

[budm]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

"With meter in diode mode and ground lead on center leg of transistor I get .13v on each of the other 2legs. With pos lead on center leg I get .OL on the other 2"
Can I see the pictures of this TRANSISTOR? The Vf reading of 0.13V sounds more like common cathode diode rectifier.

[flamike]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

hey I think I have 1 these sets with busted screen that lights up,if that would help,mine has dvd player

[kunglo27]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

Hi to all!
Wanted to thank everyone for the sound advice. I replaced the 2 capacitors and my donated tv now works! Sound but no picture...flashing red light on PSB. When the power button was pressed the blue light would come on but no picture. Thanks again!

[Dgtech]

Re: Polaroid TDA-03211c IPOS150 Power Supply Problem

I just fixed one of these yesterday too. Just the 2 caps needed replaced once again. I bought the set the other day for $20. The only thing that sucks is that the remote didn't come with it. Can someone please tell me the model number of the remote or post a picture of it?