Sony KDL-19M4000 Dead

[RanZim]

I have a Sony KDL-19M4000 Flat Screen that is dead -- no standby light.

Fuse F101 checks good.

Got servioe manual. On power supply board (G boord) connector CN101 has no voltages present. Manual has pictorial/layout of G board, but states that schematic is not available.

Traced out some of board (Wow! Never saw so many filters and flash gaps.) and have continuity from line cord connector to BD101 (bridge rectifier??).

I'm flying blind here.

Is anyone familiar with this board? Or have an idea on how to approach this problem based on other Sony TVs?

Thanks.

[stj]

Re: Sony KDL-19M4000 Dead

fotos?

[Alastair E]

Re: Sony KDL-19M4000 Dead

Any stdby 5v from PSU to MB?
--With no light--I'm guessing not....

[budm]

Re: Sony KDL-19M4000 Dead

Is this the board?
http://www.shopjimmy.com/sony-1-857-032-11-g-board.htm

Top view
http://www.shopjimmy.com/media/catal.../185703211.jpg
If it is, check the DC voltage right at the two legs of C101, C102 main filter caps.

[RanZim]

Re: Sony KDL-19M4000 Dead

Thanks for the quick replies guys.

To Budm's questions --

Yes, that is the board.

Measuring C101 and C102, all leads to ground are zero. However across the leads of each cap, I read 159 Vdc.

Also. the voltages on CN101 are not exactly zero. There are --
on the 5.5v pins --> 1.5 to 2.0 vdc, varying
on the 2.5v pins --> 1.0 vdc
on the 12v pins --> 2.5 to 4.0 vdc, varying

[budm]

Re: Sony KDL-19M4000 Dead

"Measuring C101 and C102, all leads to ground are zero. However across the leads of each cap, I read 159 Vdc." The is correct voltage, BTW, when you check the voltage on the Primary side (HOT side) of the circuit, you do not use the chassis Ground (safety ground) as the ground ref point, you use the negative leg of the main filter cap as the ground ref point, that is why I indicate to measure the voltage right at the two legs of the main cap.
It sounds like you have bad startup caps (C104, C108 on the right of the big cap) in the primary side.
Try heating that area for a few minutes with hair dryer, then apply the power to the monitor to see if it will come on.

[RanZim]

Re: Sony KDL-19M4000 Dead

Thanks for the reply, Bud. (I've been on the road a few days.)

Yes. I just automatically measured the voltage to chassis ground. But once I saw the peak voltage across the cap, I knew I was on the line side of the circuit.

I tried the hair dryer idea per your directions, but no change -- still dead.

I also was attempting to trace that part of the circuit (and draw a schematic) from the foil side of the board. But it's rather involved.

Would appreciate any other ideas/approaches you might have.

[tom66]

Re: Sony KDL-19M4000 Dead

You need to measure -across- those caps i.e. red on positive lead of cap, black on negative lead. If you like you can also place the black lead on the negative of the 450V cap which can be easier.

[RanZim]

Re: Sony KDL-19M4000 Dead

Thanks for the response, Tom. But that really wasn't an issue. I was just explaining why I measured to ground first, and then across the cap.

After thinking about the symptoms, particularly the varying voltages (see earlier post), I'm beginning to think this may be either an auto-shutdown problem, due to an overload on one of the supplies, or a kick-start issue. Of course without a schematic, the debug/analysis is that much harder.

Has anyone had any experiences with these types of problems?

Has anyone successfully (and safely) operated this PSU board without a load?

[budm]

Re: Sony KDL-19M4000 Dead

You can run the board by itself since it is an always on power supply. Do you have cap meter to measure the capacitance and meter to measure the ESR of the cap. At this point I would try replacing those start up caps first. You can load the 5V power supply with 10 Ohms 5W resistor to simulate 500mA current draw.

[RanZim]

Re: Sony KDL-19M4000 Dead

Thanks Bud. I got sidetracked with car repairs and plunbing repairs. Am now finally able to get back to the TV issue.

No, don't have an ESR meter. But I should probably buy or build one since there are a number of antique radios people want me to look at. (Any suggestions?)

In the meantime, I will replace those two startup caps.

I'll let you know how it works out.