Gateway LP2407 - No power

[Chapel Heel]

I was given a non-working Gateway LP2407 and used this thread as a guide to replacing the caps on the power board:

https://www.badcaps.net/forum/showth...ghlight=lp2407

I replaced ALL the caps except the large one, which I have verified is putting out 172v. I also verified that the output to the logic board (with a green square around it in my picture) is correct, according to post #15 in this thread:

https://www.badcaps.net/forum/showth...ghlight=lp2407


It has the following voltages (from top to bottom):

0
0
0
5.5
0
0
23.3
23.3

Still, no signs of life from the display, save for the sound of the power board powering up when plugged in. There are no bulging caps anywhere else.

My next step was to measure the outputs of the voltage regulators on the logic board, according to the info on the same post listed above. I have them numbered 1-5 on my image. Here are the part numbers and their measured voltages:

1) AS1117L-18 - Pin 3: 3.3v -- Pin 4: 1.8v
2) AS1117L-33 - Pin 3: 5v -- Pin 4: 3.3v
3) AS1117R-18 - Pin 3: 3.3v -- Pin 4: 1.26v
4) AZ1084S-3.3EI - Pin 3: 5v -- Pin 4: 3.3v
5) AS1117L-33 - Pin 3: 5v -- Pin 4: 3.3v

And that's where things stand. Where should I go from here?

1. Is regulator #3 bad and needs to be replaced?
2. Would Digikey part number AP1117E18GDICT-ND be the correct part?
3. How about the caps on the logic board and/or inverter board, does it make sense to replace them?

Thanks for your help!

[PlainBill]

Re: Gateway LP2407 - No power

I was given a non-working Gateway LP2407 and used this thread as a guide to replacing the caps on the power board:

https://www.badcaps.net/forum/showth...ghlight=lp2407

I replaced ALL the caps except the large one, which I have verified is putting out 172v. I also verified that the output to the logic board (with a green square around it in my picture) is correct, according to post #15 in this thread:

https://www.badcaps.net/forum/showth...ghlight=lp2407


It has the following voltages (from top to bottom):

0
0
0
5.5
0
0
23.3
23.3

Still, no signs of life from the display, save for the sound of the power board powering up when plugged in. There are no bulging caps anywhere else.

My next step was to measure the outputs of the voltage regulators on the logic board, according to the info on the same post listed above. I have them numbered 1-5 on my image. Here are the part numbers and their measured voltages:

1) AS1117L-18 - Pin 3: 3.3v -- Pin 4: 1.8v
2) AS1117L-33 - Pin 3: 5v -- Pin 4: 3.3v
3) AS1117R-18 - Pin 3: 3.3v -- Pin 4: 1.26v
4) AZ1084S-3.3EI - Pin 3: 5v -- Pin 4: 3.3v
5) AS1117L-33 - Pin 3: 5v -- Pin 4: 3.3v

And that's where things stand. Where should I go from here?

1. Is regulator #3 bad and needs to be replaced?
2. Would Digikey part number AP1117E18GDICT-ND be the correct part?
3. How about the caps on the logic board and/or inverter board, does it make sense to replace them?

Thanks for your help!

Excellent description, excellent pictures. That is how I like to see a thread started.

1. Yes, regulator #3 is either defective or overloaded. Since the tab is the output, replacing it is the only logical choice.

2. Yes

3. I'd replace the caps on the signal (logic) board only as a last resort if replacing the regulator does not fix it. Bad caps on the inverter did not cause this problem, but replacing them might not be a bad idea.

PlainBill

[tom66]

Re: Gateway LP2407 - No power

Yes, that is the correct part.

These 1117 series regulators seem to drop like flies; I've just found a failed one in a Samsung LCD TV.

[Chapel Heel]

Re: Gateway LP2407 - No power

Thanks, PlainBill! Just trying to make your life easier since you're kind enough to help out. I've ordered a new 1117 regulator and the caps for the inverter board. I'll post the results when I get them installed!

-Nick

[Chapel Heel]

Re: Gateway LP2407 - No power

SUCCESS! I replaced the suspect voltage regulator (and the caps on the inverter board for good measure) and the display fired right up.

I now have a different sort of problem: a high-pitched whine/buzz coming from the power board, right around the point I have circled on the attached picture. I have also determined that this noise does not occur if I unplug the inverter board from the power supply board.

The information printed on the side of the transformer is:

CHK-078
DN 0638 A
Rohs (in an oval)

Any suggestions?

[PlainBill]

Re: Gateway LP2407 - No power

SUCCESS! I replaced the suspect voltage regulator (and the caps on the inverter board for good measure) and the display fired right up.

I now have a different sort of problem: a high-pitched whine/buzz coming from the power board, right around the point I have circled on the attached picture. I have also determined that this noise does not occur if I unplug the inverter board from the power supply board.

The information printed on the side of the transformer is:

CHK-078
DN 0638 A
Rohs (in an oval)

Any suggestions?

You could try removing the tape, then soaking the windings with varnish or crazy glue. Or you could just put it back together. A buzz from that transformer is not uncommon.

PlainBill

[Chapel Heel]

Re: Gateway LP2407 - No power

I dipped it in varnish, but no luck on getting rid of the buzz. Oh well. As far as I'm concerned, it's case closed.

THANK YOU FOR YOUR HELP, PlainBill!

[tom66]

Re: Gateway LP2407 - No power

I've had luck with super glue on inductors, but you have to expose the windings first, which could be difficult.