Toshiba 40RV525U Blows Fuse

[fxdfireman]

I got a Toshiba 40RV525U that blows the main fuse on the power supply as soon as you put power to it. i checked the bridge rectifier and it tested out OK. Does anyone know of anything else that i should check on the board that would cause this.
Thanks for any help!

[mr2013e]

Re: Toshiba 40RV525U Blows Fuse

check mosfets on the heatsink and those big black caps for short.

[budm]

Re: Toshiba 40RV525U Blows Fuse

Remove the screws on that heat sink so we can see the devices attached to it. You need to test those devices for short. We also need the bottom side picutres.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

OK i will get a couple more pics after work. I think there are two mosfets on that heat sink under the plate with the screws.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

Thanks for the input, i checked the two big caps to see if they were shorted and they don't appear to be. I don't have an ESR meter to be 100% sure those caps are not bad. Here are a couple more pictures, i will check out the mosfet's on the heat sink near the two big caps tonight after work. I had a meeting last night and didn't have alot of time to look at it.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

Those 2 mosfet's on heat sink can i leave them in circut and just check resistance across the signal and gate and as long as it isn't high they should be good. Or is there something else i should be focusing on?

[tom66]

Re: Toshiba 40RV525U Blows Fuse

Yes, in circuit is fine, test all three pins 1-2, 2-3, and 1-3 both ways on diode test.

[mr2013e]

Re: Toshiba 40RV525U Blows Fuse

first remove mosfets you have to mesaure between Drain and Source like a diode test.other ways open.if they are OK. you must be sure bridge diode not short.

[tom66]

Re: Toshiba 40RV525U Blows Fuse

You don't have to remove them to see if there are shorts, but if you find one you should remove it to confirm if it is shorted or not.

[mr2013e]

Re: Toshiba 40RV525U Blows Fuse

yes of course if they are shorted, it is easy to find.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

If they are shorted they will be shorted open? Shorted to gound?

[tom66]

Re: Toshiba 40RV525U Blows Fuse

There's no such thing as "shorted open"... you'll just see a low reading between pins. On diode mode, a reading below 200 is suspect and 30 is very likely to be bad. Many multimeters show a single "1" when there is no continuity on ohms range, treat this as not shorted.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

Thanks, sorry for the newbie questions.

[tom66]

Re: Toshiba 40RV525U Blows Fuse

No problem, we all start somewhere.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

When i checked the four small blue caps in the top right corner of the first picture i posted, three of them had no continuity in either direction the other one had some both ways. Are those bad and could that be my problem or at least part of it?

[mr2013e]

Re: Toshiba 40RV525U Blows Fuse

yes it is one bad small blue cap.change it.it can cause blown fuse.i think they are varistor.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

So how do i know what type to order, i don't see any numbers on them. Is there a way to tell off the board number? Does somebody know what i need to order?

[mr2013e]

Re: Toshiba 40RV525U Blows Fuse

remove only bad one.and fix fuse.it is ready to work.but varistors are for voltage security.

[fxdfireman]

Re: Toshiba 40RV525U Blows Fuse

I was thinking of replacing all four to be safe. Do you know the specs are on these for ordering?

[budm]

Re: Toshiba 40RV525U Blows Fuse

Those 4 blue caps (by the top right of the board close to the AC input circuits) are X/Y safety caps for noise filtering. The TV will work without them in place. Show us the closed up pictures. They should show open (high resistance). Which one is showing shorted? These safety cap should not fail to shorted mode since they are safety caps.

CY101 is for Neutral to Chassis
CY102 is for Line to Chassis

CY103, CY105 are for Primary side Ground ref to Chassis.
So which one read shorted?