Memorex MLT1912

[PlainBill]

This one is personal. I have a spot reserved for it on my desk.

The patient is a Memorex MLT1912 19" Widescreen LCD HDTV. I purchased it as 'dead', and boy, was the seller right. The main problem appears to be a shorted IC, U11 on the 'TL ATSC LCD version 5' board. Pictures are attached. The first is of that area of the circuit board, the second is of the actual IC (2 legs were lost in removing it), the last is a drawing of the IC with a notch to identify pin 1.

For reference, the IC is 3 mm long. It is a smd device and appears to bear the designation A17d. I am certain about the A17, the d is my best guess. I am confident it is a voltage regulator. After much probing I have identified the following pins.

1 Control? (CN3-4 via 4.7K R87)
2 Ground
3 Power out
4 Power in
5 Feedback?

All attempts to identify a 5 pin voltage regulator with A17 in it's part number have failed; I have not found any smd IDs starting with A17 that match this package. I am searching for a schematic (yes, I'll pay for it), and have contacted Memorex for assistance. Neither have responded yet.

I'm pretty good at reading schematics, and analyzing how circuits work. I am LOST when trying to research available ICs for a particular purpose. And I'm confident that I haven't found all possible cross references for smd label to manufacturer's part number. Does anyone have any suggestions?

Thanks,

PlainBill

[Toasty]

Re: Memorex MLT1912

>>All attempts to identify a 5 pin voltage regulator with A17 in it's part number have failed;<<
Why you chop off 3 legs? You mean 8 legs, correct?

Probably not a regulator but a MOSFET.

Perhaps 3A17D? Attached.

[PlainBill]

Re: Memorex MLT1912

>>All attempts to identify a 5 pin voltage regulator with A17 in it's part number have failed;<<
Why you chop off 3 legs? You mean 8 legs, correct?

Probably not a regulator but a MOSFET.

Perhaps 3A17D? Attached.

Nope, but thanks for trying!! There are several MOSFETs (E6P02) on the board, I recognize them. Take a look at the mount area for U11. There are only 5 pads, three on one side, the end two on the other. There isn't even a solder pad for the middle pin on the second side. That eliminates the 6 pin packages. Heck, I haven't even figured out what this package is called!!

5 terminal regulators are common. The main board of this TV uses several N2596G-5's, but those are in the familiar TO263 package. This thing is tiny, about .1" long. I suspect it is a low current variation of one of the 5 terminal regulators, but which one? Googling 'voltage regulator' gets hundreds of hits from auto parts stores.

PlainBill

[Wizard]

Re: Memorex MLT1912

This is PWM buck regulator or a MOSFET switch to do power control (off or on).

I have seen these in this package type.

Cheers, Wizard

[Toasty]

Re: Memorex MLT1912

OIC. You pictured the circuit after you removed it. I'm looking at the 8 legged IC not at the U11 pad.

A pre-mangled picture would help on that last letter/number. :P

Suggestion to invest in some Chip-Quik.

[PlainBill]

Re: Memorex MLT1912

This is PWM buck regulator or a MOSFET switch to do power control (off or on).

I have seen these in this package type.

Cheers, Wizard

Thank you!! PMW buck Regulator is the name I was looking for. This part has ferrite beads on input and output AND an inductor on the output. That sounds like a regulator, not a switch.

The LTC3406BES5 is in the same package, and the pinout matches, but the SMD ID is different. Closer, Wizard is getting me closer!

PlainBill

[PlainBill]

Re: Memorex MLT1912

OIC. You pictured the circuit after you removed it. I'm looking at the 8 legged IC not at the U11 pad.

A pre-mangled picture would help on that last letter/number. :P

Suggestion to invest in some Chip-Quik.

Whatsa madda, you think I jerked the chip without looking at it first?
I used chip-quik!! I'd examined the chip closely with a magnifier before removing it. Removing SMD parts without damaging them is usually easy, but not when they are shoehorned in like this. (I had to remove the connector (CN3) to get access to U11.) Add in the difficulty that the 'magic smoke' had leaked out when the chip shorted, and well, the two missing legs are in a glob of chip-quik.

PlainBill

[Toasty]

Re: Memorex MLT1912

>>Whatsa madda, you think I jerked the chip without looking at it first?<<

No. But the before pic would've shown how this thing was mounted. Now I don't see how this was mounted. Very confusing from the shape on PCB to the device body shape.

You said the LTC3406BES5 part matched this part in shape and size. So the corner is not notched off (as the PCB shows) but flat and rectangular?

From the LTC3406BES5 datasheet it would seem this is a TSOT-23-5 package. It's not hugely popular, and Mouser shows a few regulators and converters in that package.

Digi-Key lists several hundred, but narrowing the field is some fun you can have while you're twiddling you thumbs.

Toast

[PlainBill]

Re: Memorex MLT1912

>>Whatsa madda, you think I jerked the chip without looking at it first?<<

No. But the before pic would've shown how this thing was mounted. Now I don't see how this was mounted. Very confusing from the shape on PCB to the device body shape.

You said the LTC3406BES5 part matched this part in shape and size. So the corner is not notched off (as the PCB shows) but flat and rectangular?

From the LTC3406BES5 datasheet it would seem this is a TSOT-23-5 package. It's not hugely popular, and Mouser shows a few regulators and converters in that package.

Digi-Key lists several hundred, but narrowing the field is some fun you can have while you're twiddling you thumbs.

Toast

No, no obvious mark on the IC indicating pin 1. With only 5 pins it's not too hard to tell. The printing on top is another clue.

I figure I have a couple of approaches to identifying this. Looking at the board, there are ferrite beads on input and output. That certainly seems like something that would be used with a high frequency (>1mhz) bucking regulator. A search MIGHT find the proper manufacturer, then narrowing it down to a specific IC becomes easier. After all, I can't count on Digi-Key to carry this particular manufacturer.

The other thing is there are only 5 LSI chips on the board. I've found data sheets for three of them. By tracing the output of this chip to a particular IC I can establish what the output voltage is supposed to be. At that point I can do the research in the 'normal' direction, choosing the chip by it's specs, not by the smd ID.

PlainBill