Tuesday, October 23, 2012

Testing TOM277CABB for Digital Lifestyles LT42332 / FA2B-42570

Synopsis: This article talks about how to test if your STARMEN TOM277CABB power board is bad and points to a repair service and exchange service , if available, in case you need them.

*** Update with fast links ***
A few days ago we were asked to repair a power board TOM277CABB made by STARMEN .
It is used in a number of 42'' LCD TVs such as Digital Lifestyles FA2B-42570, LT42322, ARION AD-LC42F, SOYO MT-SYTPT4227AB and possibly others.
Since Digital Lifestyles is now out of lifestyle and since it was a low end brand to start with (which doesn't necessarily means the TVs were of bad quality) there is no technical documentation available for it and that makes troubleshooting a bit harder.

Here is how TOM277CABB looks like (click to enlarge):

If you doubt that your power board is bad what you can do and should do is test it independently from the TV to see if it provides the standard standby power voltage (+5V SB) and then , if signaled by the main board, the rest of the voltages it is supposed to generate.

All it takes is a simple voltmeter and knowledge where the output voltages are on the board.

Upon connecting the board to AC the only output voltage it should generate is the +5V standby.

Then, when those 5V standby are passed to a dedicated "power on" (wake up) pin the rest of the board activates and generates the 5V/4A, 12V/3A and 24V/9A powers as indicated on its label above the large transformer at the top (see picture).

More civilized manufacturers label connector pins / meanings, but apparently STARMEN isn't among them, so here is the layout for you (again, click to enlarge):

As you can see the lower two power connectors are only used for the back light inverters; they are connected in parallel and they only provide the +24V inverter power.

The single connector above them is the one used to control the board and also provide power to the main board.

The only power you should find on it when connecting the board to AC is the +5V SB voltage measured to any of the ground pins (I used the rightmost ones on any of the lower connectors for ground).

And when you short those +5V to the POWER ON pin, which is extremely easy since it is right next to the +5V, the rest of the voltages should come up.


Probably the most common issue with the board will be the failing electrolytic filter capacitors at the board's outputs (can be seen between the heat sinks at the left side of the board at the top picture - groups of 4,3 and another 3 capacitors).

When those go bad they are usually easy to tell visually as their tops are bulging and sometimes leaking electrolyte; sometimes it may be the bottoms as well.

The second issue we have seen on the board is a blown main fuse F1 caused by a failed/shorted transistor Q1; while we have not seen it at the time of this article, failure of such a transistor can sometimes take down other less powerful components as well, so be aware and check around as well.

We offer DIY repair kits for STARMEN TOM277CABB and we may add or modify them over time as more information comes in and demand changes.

Also, when available, we may be able to offer an exchange service for STARMEN TOM277CABB.

Finally, if the matter is not just a swollen capacitor, you may consider using our TOM277CABB repair service.


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