Sharp LC-42SB48UT-a no standby voltage

[AcGeorgiegirl]

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

Ok, points well taken, thanks! I'll check my dmm's battery. One thing, though....if the meter's reading is a bit off(lower v's), wouldn't the tv power on, at least(given that the 4.04 standby is possibly lower than the needed 5 volts)?

[budm]

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

If the meter is showing 4.04V but the power supply is actually putting out 5V, then you have problem in the main board, since the TV was worked on by someone else before you, you may want to look at the main board really well to see if anything were left out, unsoldered, etc.

[AcGeorgiegirl]

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

...ok, but I've not connected the main to the psb when it's reading 4.04?

[budm]

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

...ok, but I've not connected the main to the psb when it's reading 4.04?

But we do not know if your meter is correct at this point for sure.

[AcGeorgiegirl]

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

I checked the battery of my DMM...it's good.

[jts1957]

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

"Measure" another battery. Report battery 'type' and reading you obtained.

[AcGeorgiegirl]

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

"Measure" another battery. Report battery 'type' and reading you obtained.

AA 1.45
AA rechargeable(freshly charged) 1.23
D 1.55

[budm]

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

So it lookds like you meter is OK.
There are parts that are used for regulating the output of the 5VSTBY:
IC913 (Vref diode xx431??, IC911 (OPTO), Voltage divider for the IC913.

[AcGeorgiegirl]

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

I've tested ic's before without removing them from circuit, but there were very few linear components of them. Is this acceptable in this situation, or do you suggest I remove a leg of each?

[jts1957]

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

Do you have a external 5 volt supply that you could connect to the lower than normal 5V to see what happens?

[budm]

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

Can you please verify that the SMPS for the STBY is TNY277?

[AcGeorgiegirl]

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

Do you have a external 5 volt supply that you could connect to the lower than normal 5V to see what happens?

I don't know(!). I do have other psb's from 3 different tv's. What would work? Would this be a jumper to the 5v pin from the external source? I have a multi-use household charger that can be set to lots of voltages. I can't think of any batteries that are 5 volt.

[AcGeorgiegirl]

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

Can you please verify that the SMPS for the STBY is TNY277?

I'll look at the schematic. I'll go ahead and post here, too.

[jts1957]

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

Can you please verify that the SMPS for the STBY is TNY277?

It was in my 42".
Btw I see '5V' on schematic (top of C934). Did they leave 'STB' off?

[budm]

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

The P/N of the IC I got it from the pictures of the board from shopjimmy.

[AcGeorgiegirl]

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

I don't know how to find it, so sorry.

[budm]

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

I'll look at the schematic. I'll go ahead and post here, too.

You have the schematic?
OK, I download the service manual from ELEKTROTANYA.
My manual show TNY277, your manual shows something else.
Please look at what is actually printed on top of the IC903.
Where did you get the manual from?

[AcGeorgiegirl]

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

I posted just above your last post. See it?

[jts1957]

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

The P/N of the IC I got it from the pictures of the board from shopjimmy.

SM available at ElektroTanya.

[dick_barton]

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

Service manual attached with power supply schematic, hopefully