Memorex Model MLT3221

[C22]

This Memorex 32 inch LCD has a power supply board made by Proview. It is assembly number IPOS 150 Rev 1.8. The screen went dark. Upon examining the board. EC 17 and EC18 (Aluminum Electrolytic capacitors) 10 MF, 450 V, 85*C had bulging tops. Replaced them with Radio Shack (Aluminum Electrolytic caps) LTE,10MF, 450 V, 105 *C. Picture is back and TV is working.
But there is a large capacitor designated as FC2, presumably a filter cap. It is unusually marked like 25/105/V36. I would interpret this to be 25 MF, 105*C, 36 Volts, but I have not seen a cap marked like this before. My concern is that the top is bulging and I feel it may be stressed, so I would like to replace it.

It is the large cap laying down between the heat sinks. I don't have a parts list so I'm unable to know the true value.
This Proview board is also used in Polaroid LCD TVs. Model TDA-03211C comes to mind.
Help

[budm]

Pictures of this cap?

[cashkennedy]

He tried linking the picture, but he linked a picture that was on his own computer, so the link is obviously invalid.

If you want to post pictures on this site you need to use the manage attachment function anyways, not just link them in the message.

To use manage attachments, go to reply (not quick reply), and scroll down below where you type the message, and you should see a manage attachments button.

[C22]

Repeat of upload of mlt3221 cap pic. Does this work?

[C22]

OK, I guess it did.

[budm]

I can see on the top left of the pictures, two caps with domed top, but I cannot see FC2. ThisMAGMEET power supply looks familiar, full pictures of the power supply?

[selldoor]

Hi This board has featured before here is one like it http://badcaps.net/forum/showthread.php?p=173355. But cap description slightly different - i have seen a few
with slight differences 36v 37v 40v.
I think you will be correct in thinking 25uF, 105*C, 36 Volts, but as you board is working
you can check the voltage across the cap - polarity is important.

[budm]

Its value is 150uF 450VDC. This power supply has PFC Voltage booster circuits. 165`170Vdc when TV is OFF, about 380~400Vdc when TV is ON.

[C22]

These may be better photos of FC2 of this mlt3221.
Thanks

[budm]

It is 150uF 450VDC

[selldoor]

Originally Posted by budm

It is 150uF 450VDC

Hi Budm - just as a learning thing where did you find that out?

[retiredcaps]

Originally Posted by selldoor

Hi Budm - just as a learning thing where did you find that out?

Just remember that this big filter cap has to be at least > 120V x 1.4141 or > 220V x 1.4141 since it is on the hotside so there is no way it can be 36V.

My guess is that budm has worked on this before and probably consulted his own notes at

http://s807.photobucket.com/albums/y...orex%20MLT3221

[budm]

I have the whole controller box with me, I had to lift the cap up to see the marking. This model is almost exactly the same as Polaroid.
Yes, I worked on these power supply before, and he should changed those two caps from Radio Shack with low ESR type, otherwise they will go bad again, he was lucky that they did not take out the two MOSFETs when the caps went bad. Use PANASONIC FM/FC/FR series instead. 36VDC cap would have blown right up. Power supply will always has large 250vdc minimum (for US, Higher for Euro) for the Main DC on the primary side to supply the power.

[selldoor]

Thanks Budm - when you say "I had to lift the cap up to see the marking" are they marked differently on the other side - hypothetically If I found one in a box of bits is there any way of knowing what rating it is.

[budm]

The printings were on the other side of the cap, I had to pry the body up to see the cap value and the voltages. You can check the capacitance value and ESR (if the cap is still good) with the meter but not the working voltage of the unknown cap.

[Dgtech]

Be certain that you replace the main common defective components. The two caps closest to the two large transformers are 10uf 450 volt capacitors.
I would normally say not to change the large one. I'd try the two first and then see what you got after that.

[budm]

He did replace them with the caps from RS "The screen went dark. Upon examining the board. EC 17 and EC18 (Aluminum Electrolytic capacitors) 10 MF, 450 V, 85*C had bulging tops. Replaced them with Radio Shack (Aluminum Electrolytic caps) LTE,10MF, 450 V, 105 *C. Picture is back and TV is working."

[Dgtech]

Sorry, just caught that. Working nightshift has my "attention to detail" screwed. LOL

[C22]

Budm: Thanks from C22. I will replace RS caps with Panasonic caps for good measure. Copy the 150MF@ 450V. Will use Panasonic for that one also.
Appreciate your input.

[budm]

Trick to remove that large cap that is glued down, mark the Positive and Negative legs on the board, then use razor blade to cut a line on the tubing of the cap, cut the legs off the cap then you will be able to easily lift the cap body off the board. This will make it easier to remove the tubing which is glued to the board, and the legs will be easily removed also.
Another reason is that we do not want to flex the board too much, you may crack the surface mounted MLC (multilayer ceramic) caps.
http://www.badcaps.net/forum/showthread.php?t=19663