Akai LCT3285TA LCD TV power supply issues

[Nam3o]

I am working on the power board for this TV. I attached pictures of it below. the three caps in a row are all swelling and need to be replaced.
There are two caps under the heat sink that are also swelled but i cant ID them without removing the sink.

Is there an easy way to remove the heat sink, or do do i have to un-solder the pins that hold it down?

the model number of the board is MLT169B REV. 1.1 2006.05.13

[retiredcaps]

Re: Akai LCT3285TA LCD TV power supply issues

I am working on the power board for this TV. I attached pictures of it below. the three caps in a row are all swelling and need to be replaced.

The little one nestled in with the 3 in a row looks also bad.

Is there an easy way to remove the heat sink, or do do i have to un-solder the pins that hold it down?

Many here will suggest that you replace ALL the electrolytic capacitors since you have almost a 50% failure rate on the caps. They also look like Capxon brand and they are more than 4 years old. Capxon doesn't have the greatest reputation here on this board.

EDIT:

So if you are going to replace them all, unsolder the heat sink.

Be sure to use high quality low ESR capacitors from this list.

https://www.badcaps.net/forum/showthread.php?t=2280

Alternatively, if you live in the USA, follow PlainBill's instructions to order Panasonic FM caps (if out, substitute FC). Note his warning on the diameter and height measurements.

https://www.badcaps.net/forum/showpo...33&postcount=2

[Nam3o]

Re: Akai LCT3285TA LCD TV power supply issues

Thank you for your reply. I was considering replacing all of them but I have not identified them all to find suitable replacements.

[retiredcaps]

Re: Akai LCT3285TA LCD TV power supply issues

I was considering replacing all of them but I have not identified them all to find suitable replacements.

See my edited post #2.

[PCBONEZ]

Re: Akai LCT3285TA LCD TV power supply issues

I did an MLT168A a while back which is very similar to the one you have.
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I'm pretty sure some of the caps in those Megmeet PSU's need to be better than FM due to the phsical size of the originals. [To keep Ripple/ESR as original.]
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Is that row in the center [bloated ones] 1000uF @16v?
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If you can post what you've found [make, series, uF, volts, diameter] there's a whole bunch of folks here that can guide you to good replacements.
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Attached is the BOM from the one I did.
.

[Nam3o]

Re: Akai LCT3285TA LCD TV power supply issues

All original caps are capxon.
470uf 35v. X2
1000uf 35v. X2
1000uf 16v. X3
220uf 25v. X2
22uf 50v. X2
10uf 50v. X4
100uf 450v. X1
22uf 450v. X1
All of them are high temp.

[PCBONEZ]

Re: Akai LCT3285TA LCD TV power supply issues

Can't 'spec' them without series name and diameter. [And in some cases length.]

For example Capxon probably makes 470uF 35v in 20+ different grades each of which will have it's own series name and spec sheet.
Some of those series will have more than one physical size of 470uF 35v and the specs will be different because the can size is different.
[Within a series,, a bigger can means lower ESR and higher Ripple ratings.]

Don't worry. It will all come together eventually.

Step 1 in choosing new caps for something like this is to look up the ESR and Ripple of the old caps.
In aid of that:
The Manufacture name tells you where to look for the data sheet.
The Series name tells you which of their data sheets to look in.
The uF, volts, and physical size tell you which caps to look at in the table.
- Kinda need all of it.
.

[Nam3o]

Re: Akai LCT3285TA LCD TV power supply issues

I don't know exactly what you need but here are the other numbers on the caps.

470uf 35v. X2 c624 vent
1000uf 35v. X2 c628 vent
1000uf 16v. X3 c626 vent
220uf 25v. X2 c624 vent
22uf 50v. X2 c626 vent
10uf 50v. X4 c628 vent
100uf 450v. X1 c624 vent
22uf 450v. X1 c538 vent

[Nam3o]

Re: Akai LCT3285TA LCD TV power supply issues

can I use higher voltage replacements?

also i cant find the 100uf 450v caps anywhere.

[PCBONEZ]

Re: Akai LCT3285TA LCD TV power supply issues

The series name is like a model number for the product line.
It's generally a 2 to 4 digit letter/number string written on the cap.
.
In the attached pic I zoomed in on and circled the only series mark I can make out in your photos.
-
It happens to be a KF series but I dunno which cap in your list it is so I can't tell you anything else about it.
-
I can't tell you about any others in your list because I dunno what series or how big they are.
-
I will attach the KF data sheet too.
That will help you learn how to look up cap specs at least for any KF you have.
.

[PCBONEZ]

Re: Akai LCT3285TA LCD TV power supply issues

Now,
If you look in the KF data sheet at 2200uF/6.3v you will see the rest of what I'm trying to get across.
There are -two- sizes of KF 2200uF 6.3v and they have different specs [because their physical size is different].
-
KF doesn't have a lot of this going on but other series do.
Some series have 3 or 4 can sizes for some of the uF/volts combinations.

USUALLY Diameter is all that's needed to differentiate when uF and volts are the same in two can sizes in a series spec table but once in a while you will run into the situation where some uF/volts combination has short and long caps in the same diameter. In those cases you will also need to know length to get the specs.
.

[PCBONEZ]

Re: Akai LCT3285TA LCD TV power supply issues

In this kind of PSU you want to make darned sure:
- You do not use caps with a lesser Ripple rating. [want the same or more]
- You do not use caps with higher ESR. [want the same or less]
.
The KF data sheet is calling ESR 'Impedance'.
Other makes use other terms.
Just look for "Ohms at 20C and 100kHz" and you are in the correct column for Low ESR caps.
-
General purpose caps simply don't list it so go by Ripple only.
- Good to use entry level Low ESR caps for those anyway though.
-
If you trip over some cap that is rated at 100Hz or 120Hz instead of 100kHz the look for replacements rated at the same frequency -or- there is usually a conversion chart somewhere in the data sheet for 'good brands'.
.

[kc8adu]

Re: Akai LCT3285TA LCD TV power supply issues

fm are fine in the megmeet cap bakers.
the 10's 22,47,ect fc is fine.
all the secondary get fm here.
btw look under all the heatsinks.a few little ones buried under them.

[Nam3o]

Re: Akai LCT3285TA LCD TV power supply issues

Wow thank you for the info. It should be fairly obvious to everyone that I am just getting started with all this, I don't have a background in electronics so I am getting a little lost on some of this. I will try my best to understand but I do appreciate the help.

[PCBONEZ]

Re: Akai LCT3285TA LCD TV power supply issues

You'll get it eventually.
Everyone has to start somewhere.
.

[Nam3o]

Re: Akai LCT3285TA LCD TV power supply issues

I did get it. Thanks so much for your help everyone.

[1simtime]

Re: Akai LCT3285TA LCD TV power supply issues

Nam3o - anyone?
Do you still have the pictures of the power supply? MLT169B REV.1.1 used in LCT32XXXX ILO AKAI and VIORE .
I am trying to find the value of the resistor between T3 and heat sink 1 ( R68) Thanks

[1simtime]

Re: Akai LCT3285TA LCD TV power supply issues

The resistor I removed appears to be Black/Yellow/White/? can't read (Looks like it got hot) measures 95K.

I was told that R68 is 68K 1/2 watt .I guess I will try that .

I also found Q11 bad in case anyone else was having the same problem.

[mshoopman10]

Re: Akai LCT3285TA LCD TV power supply issues

MY POWER SUPPLY HAS BEEN HIT WITH A SURGE DURING A LIGHTNING STORM. DO ANYONE THINK I SHOULD TRY TO REPAIR THE PROBLEM OR JUST REPLACE THE ENTIRE POWER BOARD. WHICH WOULD WORK BETTER AND BE MORE COST EFFECTIVE. I FOUND AN UPGRADED BOARD 24A INSTEAD OF 16A FOR 132.99. CAN I REPAIR ALL DAMAGE PROBABLY CAUSED BY A LIGHTNING STRIKE AND UPGRADE THE COMPONENTS TO THE 24A STANDARDS THAT IS NOW RECOMMENDED. IF ANYONE HAS INSTRUCTIONS ON HOW TO UPGRADE AND WHAT ALL I SHOULD REPLACE. I AM A ROOKIE WHEN IT COMES TO THESE ELECTRONIC REPAIRS. I KNOW HOW TO REPLACE COMPONENTS WITH THE SAME BUT I NEED HELP FIGURING OUT WHAT PARTS I NEED TO USE INSTEAD OF THE SAME AS FACTORY TO MAKE THE POWER SUPPLY MORE RELIABLE AND LONG LASTING. ANY HELP WILL BE GREATLY APPRECIATED. THANKS,
MIKE SHOOPMAN


PS THIS IS MY FIRST TIME SO BREAK IT DOWN FOR ME IN LAME-ONS TERMS. THANKS AGAIN

[PCBONEZ]

Re: Akai LCT3285TA LCD TV power supply issues

Trying to fix something after lightning damage is very often a waste of time.
It's not real likely that damage was limited to your power board.
You'll have to check everything. And I mean EVERYTHING.
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You can learn a lot trying and you might get lucky but don't get your hopes up.
.