Toshiba 42rv530u wont power on

[bleed4me]

Picked this TV up with symptoms of not powering on, standby light works and is red but unit wont power on. First thing I checked was the fuses and sure enough one was bad. Replaced the 2.5A fuse and the second I powered it on it blew. The first by the AC plugin is just fine. Any insight and help with this would be much appreciated. Sorry for the poor quality picture. As for a fair warning im new testing rectifiers and mosfets so if that is what is causing the issue please be patient with me.

[CapLeaker]

Re: Toshiba 42rv530u wont power on

Right next to that fuse is that long heat sink with 2 mosfets and a diode. Check if those are shorted with your DMM in diode mode. If they are shorted, they are bad.

Maybe you want to youtube on how to test bridge rectifier, diodes and mosfets. Lots of info there.

[dick_barton]

Re: Toshiba 42rv530u wont power on

Check with your meter set to ohms to see if there is a short circuit (0 ohms) on the left hand side or right hand side of the fuse as shown in the picture.
If it's the left side then it looks like the IC with many legs as shown in the block.
If there's a short on the right side then the mosfet (Q821) or the diode (D821) or both are short circuit.
Connect black lead to negative pin of C820 and red lead to check each side of the fuse holder with no fuse in place and power disconnected from the mains.

[bleed4me]

Re: Toshiba 42rv530u wont power on

Thanks Dick barton and CapLeaker. If I position the board like the picture you provided and test for a short circuit on the fuse holder I get a constant 16.6 on the left hand side and something weird happens on the right side. For the most part it starts at 26.6 and slowly goes down and on a few occasions it jumps to 29.4 real fast then goes to 0.L, I dont understand what that means. Also while doing this test I noticed something else on T821 pin 4 has no solder on it at all just want to confirm if this is normal or not.

[dick_barton]

Re: Toshiba 42rv530u wont power on

That non connection is fine. The pin is not used so no connection.

What are the numbers given on the 3 devices, i.e. diode, mosfet and multipin IC all shown in the above picture.

When you gave the above readings what was you meter set to.

[vinceroger69]

Re: Toshiba 42rv530u wont power on

what is the power supply board number?

[CapLeaker]

Re: Toshiba 42rv530u wont power on

what is the power supply board number?

pe0546

[vinceroger69]

Re: Toshiba 42rv530u wont power on

in the repair kits for this fault looks like just two parts

Fuse F820
PFC driver IC Q860A maybe worth checking these first is this also the fuse that blows?

[bleed4me]

Re: Toshiba 42rv530u wont power on

dick_barton- Crazy as it sounds the DMM was on ohms, I even changed the battery to see if that was the issue. I just rechecked those readings and the same thing happens, first attempt if jumps to 39 then to O.L and second try it starts at 28 and counts down slowly. As for the numbers they are as followed
Q860A- STR-Z2589 8208
D821- N2206 8205
Q821- FM J07 FCPF 11N60T
Q820- FM J07 FCPF 11N60T


vinceroger69- The fuse the keeps blowing is indeed F820, and how would one test the PFC driver IC? As for the board number like CapLeaker said is PE0546 and according to shopjimmy the part number is 75010942

[budm]

Re: Toshiba 42rv530u wont power on

So the readings you are getting is in OHMS. K OHMS, or M OHMS?

[bleed4me]

Re: Toshiba 42rv530u wont power on

Sorry M OHMS , keep forgetting to look at that

[budm]

Re: Toshiba 42rv530u wont power on

If you have shorted/bad devices, it will be very very low Ohms range.
So are you sure that you tested the correct devices? There has to be shorted circuit to blow fuse that size.

[bleed4me]

Re: Toshiba 42rv530u wont power on

That test was C820 to either side of the fuse holder...

[budm]

Re: Toshiba 42rv530u wont power on

OK, the only load for that F820 fuse is that STR-Z25XX series, so the internal short may be half of the bridge drive power MOSFETs may be shorted out.
You need to check the resistance between pin 5 and pin 1 (for the upper MOSFET), then pin 1 and pin 21 for the lower MOSFET to see if one of them is shorted out or has very low resistance. Make sure you count the pin correctly.
PDF of the power supply PE5046, there are two revisions.

[bleed4me]

Re: Toshiba 42rv530u wont power on

Thanks budm for the PDFs, but I will be honest with you and that is more or less a foreign language to me. I hope one day I will be able to understand all that. In the mean time I will study it and try and make some sense of it all. As for pin 5 and 1 I get a resistance of 3.9 ohms and pin 1 and 21 I get 12.8 ohms.

[budm]

Re: Toshiba 42rv530u wont power on

Thanks budm for the PDFs, but I will be honest with you and that is more or less a foreign language to me. I hope one day I will be able to understand all that. In the mean time I will study it and try and make some sense of it all. As for pin 5 and 1 I get a resistance of 3.9 ohms and pin 1 and 21 I get 12.8 ohms.

That means when you read 5 and 21 is should show around 16 Ohms, which you should also see that when you test between the Negative leg of the main filter cap and the output side of the fuse.

[bleed4me]

Re: Toshiba 42rv530u wont power on

Thanks Dick barton and CapLeaker. If I position the board like the picture you provided and test for a short circuit on the fuse holder I get a constant 16.6 on the left hand side and something weird happens on the right side. For the most part it starts at 26.6 and slowly goes down and on a few occasions it jumps to 29.4 real fast then goes to 0.L, I dont understand what that means. Also while doing this test I noticed something else on T821 pin 4 has no solder on it at all just want to confirm if this is normal or not.

So the constant 16.6 on the left side makes sense and the right side is the issue, meaning the mosfets and diodes? grrrrrr....

[budm]

Re: Toshiba 42rv530u wont power on

Sop it is 16.6 Ohms, not 16.6 M Ohms then.
You need new IC.

[bleed4me]

Re: Toshiba 42rv530u wont power on

The left side of F820 is ohms and the right side is the M ohm. Yes when I tested 1-5 and 1-21 that is in ohms not M ohms.

[bleed4me]

Re: Toshiba 42rv530u wont power on

That means when you read 5 and 21 is should show around 16 Ohms, which you should also see that when you test between the Negative leg of the main filter cap and the output side of the fuse.

Yes when I test pin 5 and 21 I do get 16Ohms and I also get 16Ohms between the Negative leg of the main filter cap and the output (left side) of the fuse. Wouldnt a higher Ohm suggest it was good or do I have that backwards?