Sharp LC-42SB48UT-a no standby voltage

[AcGeorgiegirl]

I've looked the psb over, and find no obvious caps issues, and the 2 fuses are good. I thought of testing the ac input to start with, but haven't found how to do this. My wall outlet reads fine. Otherwise, I'm assuming I'd need to dive into testing individual components? Diodes, transistors, resistors, etc....but I can't make sense of the schematic in the service manual I've found(well, I wouldn't be able to with ANY schematic, for the most part!). Also, my service manual actually has a different psb shown for my tv. It's not even close to what mine looks like.(and, yes, I confirm it is the correct manual- but not the paper one-one I downloaded).
I am ok in testing the components, as far as that goes...but don't know what the numbers mean, if I don't have their correct voltages, right?

[budm]

Re: Sharp LC-42SB48UT-a no standby voltage

Check the DCV between the two legs of the big main filter cap in the primary side to see if you have 160~165VDC on it or not first.

[CapLeaker]

Re: Sharp LC-42SB48UT-a no standby voltage

Post the DC voltages measured on the connector top right including the pin out name.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

Check the DCV between the two legs of the big main filter cap in the primary side to see if you have 160~165VDC on it or not first.

I'm assuming I'd have to completely remove the cap from circuit first, right? I don't have an esr meter, but do have one with ohm's.

[dick_barton]

Re: Sharp LC-42SB48UT-a no standby voltage

Put your meter on DC volts and place one of the meter probes on each of the legs of C907 and power the set up. What reading do you get.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

Put your meter on DC volts and place one of the meter probes on each of the legs of C907 and power the set up. What reading do you get.

I get 2 with meter set at 500v. This is with the set plugged into outlet.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

Sorry, I accidentally replied directly to another posting...the meter reads 2 with it set at 500v. Tv plugged in, but, of course, not powered on.

[budm]

Re: Sharp LC-42SB48UT-a no standby voltage

I get 2 with meter set at 500v. This is with the set plugged into outlet.

Meter set to DCV? If that is the case, then you need to check the main AC fuses (you have two main AC fuses), the bridge rectifier.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

Post the DC voltages measured on the connector top right including the pin out name.

No voltages on any of the pins.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

Meter set to DCV? If that is the case, then you need to check the main AC fuses (you have two main AC fuses), the bridge rectifier.

Each fuse reads 0.2 with an ohm's 200 test.

[dick_barton]

Re: Sharp LC-42SB48UT-a no standby voltage

Sorry, I accidentally replied directly to another posting...the meter reads 2 with it set at 500v. Tv plugged in, but, of course, not powered on.

You need to switch on the set to measure this voltage.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

You need to switch on the set to measure this voltage.

I'm confused, sorry....there's no standby voltage, and it won't power up.

[budm]

Re: Sharp LC-42SB48UT-a no standby voltage

Each fuse reads 0.2 with an ohm's 200 test.

So the meter is set to dcv when you check the Voltage between the two legs of the main filter cap C907?
"Sorry, I accidentally replied directly to another posting...the meter reads 2 with it set at 500v. Tv plugged in, but, of course, not powered on."
You need to find out if you are getting 120VAC between the two inner legs of the bridge rectifier BD901.
You MUST be real careful since you are working in the HOT DEADLY side of the circuit.

Sharp ADTVA2415SA4 Power Supply for LC-42SB48UT

Pictures provided by shopjimmy.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

Can someone help me identify what this board's bridge rectifier is? I see nothing that looks like the ones I've seen before. I'll test it, as suggested, if I can find it!

[budm]

Re: Sharp LC-42SB48UT-a no standby voltage

Look at the designator a BD901 as printed on the board.https://www.badcaps.net/forum/attach...2&d=1466534208

Bottom left corner of the board.
You just need to find out if you do have 120VAC feeding the bridge two inner pins. See post #13.

[dick_barton]

Re: Sharp LC-42SB48UT-a no standby voltage

The bridge rectifier is BD901

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

Oh, boy. It has apparently been de-soldered by someone...the pins are staying put, but solder is missing on the ends of the pins. I can't remember if maybe I'm the one who did this, planning to pull the part and test it?! I have no idea. Anyway, my question is..can I test the pins as it sits, or do I need to add solder to the pins' ends?....(would it not read true unless it's in circuit)?

[dick_barton]

Re: Sharp LC-42SB48UT-a no standby voltage

I would solder it back in neatly and then do the check.

[AcGeorgiegirl]

Re: Sharp LC-42SB48UT-a no standby voltage

I went ahead and tested it as is, to begin with. With the + probe on the - pin, the ac's read 514 & 521. With - probe on the - pin, the reading doesn't change. I'll now go ahead and solder the pins to the board and re-test.

[dick_barton]

Re: Sharp LC-42SB48UT-a no standby voltage

Put the red lead on "+" and the black lead on "-" and the meter to DC volts.