Sharp LC-42SB48UT-a no standby voltage

[AcGeorgiegirl]

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

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

It's 17.4

[budm]

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

It's 17.4

The meter is good?
What ACV do you get between the two inner legs of the bridge rectifier? 120VAC?

[AcGeorgiegirl]

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

...I think you mean to set dmm on acv, and put - probe to - pin...then check the 2 ac pins with the + probe?

[budm]

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

You have two inner legs (2) of the bridge rectifier, we are measuring AC so it does not matter which color probes go to which inner pins, same way as you read your AC wall outlet as you indicated in post 1.

[AcGeorgiegirl]

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

Ok. There is no reading change on either of the ac pins. I've set my DMM to ACV, and there are 2 levels ....500 and 200v.

[AcGeorgiegirl]

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

I haven't yet added solder to the bridge rectifier's pin ends, just fyi.

[budm]

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

I haven't yet added solder to the bridge rectifier's pin ends, just fyi.

Well, you need to solder everything back in place first before making any Voltage measurement.

[budm]

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

BTW, what is the history of this TV? Someone worked on it before you?

[AcGeorgiegirl]

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

BTW, what is the history of this TV? Someone worked on it before you?

Yes, I think the bridge was de-soldered by the person who gave it to me. He says that is all he did.

[budm]

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

So do you get 120VAC between the two inner legs of the bridge now after you solder the legs?
I wonder if the person unsolder the legs trying to locate shorts.

[AcGeorgiegirl]

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

Please bear with me, BUDM, I'm wanting to make sure I do this right....for the bridge ac test, plug tv into outlet, then I use acv setting on my dmm and I just touch either probe to the inner pins, one at a time, to test them? New info...the standby is now reading 4.04v(after me re-soldering a diode and adding solder back to the bridge rectifier's 4 pins).

[AcGeorgiegirl]

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

...and the filter cap now reads 165v, with tv plugged in, but not switched on. Tv won't switch on.

[budm]

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

So you now have 4.04Vdc STBY? Not 5V?
Disconnect the cable between the power supply and the main board to see if you will get 5VDC.

[AcGeorgiegirl]

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

Bridge rectifier reads 521 and 514 on the 2 ac pins. I set dmm to diode mode, tv not plugged in.

[AcGeorgiegirl]

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

So you now have 4.04Vdc STBY? Not 5V?
Disconnect the cable between the power supply and the main board to see if you will get 5VDC.

Cable was already disconnected.

[budm]

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

Well, then more digging to do to find out why you are only getting 4.04VDC instead of 5VDC.

[AcGeorgiegirl]

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

Yeah, back to square one, I guess. Never had this happen, in the several I've fixed. Hate it...I'm working on a few different sets that I'd hoped to get going for a school that needs them. Can you point me as to where to start, by any chance???

[jts1957]

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

A little constructive criticism: I think you should start with the TV in the condition with everything soldered in / plugged in / boards secured. Back cover should be off. Then follow the instructions one by one.

[vinceroger69]

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

May also be worth installing a new battery in your meter incase its giving false readings and may be worth checking a brand new battery with your multi meter and seeing what voltage its reading just incase your meters under reading etc

[budm]

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

may also be worth installing a new battery in your meter incase its giving false readings and may be worth checking a brand new battery with your multi meter and seeing what voltage its reading just incase your meters under reading etc

+1