Toshiba 42HL67US blows fuses.

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

Take the resistance reading of pad 1 and pad 4 where the rectifier was soldered to those pads, I believe you have shorted load.
The four pin device ont he heatsisnk looks like anothe bridge also.

tested this just now..

in ohms at 200 setting...

i get .8

do power boards commonly have two bridges?

[tom66]

Re: Toshiba 42HL67US blows fuses.

.8 both ways? Definitely something badly shorted there.

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

by both ways i mean swapping red and black probes...

[tom66]

Re: Toshiba 42HL67US blows fuses.

Yep. So, the way to find the short is to isolate parts of the circuit until the short disappears.

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

Yep. So, the way to find the short is to isolate parts of the circuit until the short disappears.

ok what do you think i should try next.. mosfets?

if so there seem to be like 6 on here. 3 in one location all on 1 heat sink.. and 3 each on their own heat sink?

ok i am trying to test what i think are mosfets..they have 3 terminals.. but somewhere on here i read they should have a "Q" mark on board.

all my "mosfets" seed to start with a "D". does that seem right?

[tom66]

Re: Toshiba 42HL67US blows fuses.

MOSFETs will almost always be labelled "Q", and will be on the primary side. The primary side is the part connected to the mains connector and is indicated by a thick line on the bounds usually.

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

i am including some images of board so you can see the "D" i am referring to

[tom66]

Re: Toshiba 42HL67US blows fuses.

Those are the secondary side diodes -- no need to check them yet.

The primary is to the right of the white line snaking around the board.
https://www.badcaps.net/forum/attach...6&d=1364930007

[tom66]

Re: Toshiba 42HL67US blows fuses.

Isn't the 200V/560u cap in this image bulged?
https://www.badcaps.net/forum/attach...7&d=1364930007

That may be the fault! (A bulged high voltage cap can short.)

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

Isn't the 200V/560u cap in this image bulged?
https://www.badcaps.net/forum/attach...7&d=1364930007

That may be the fault! (A bulged high voltage cap can short.)

first, and i am lol a bit, i am very new to all this tv stuff.. i repair pcs.. and build pcs. so i usually just replace parts, board, and build..

yes that capacitor does look a bit rounded to me now that you have better eyes than me and i got the board in front of me ( that what i am lol about)

ok that capacitor is very close to fuse also.. how in the world would i check that or remove as i am aware that caps can shock you..

[tom66]

Re: Toshiba 42HL67US blows fuses.

Since you have a short across the bridge rectifier the cap should be safe.
Remove the cap then check the resistance across it, and also across the terminals where you removed it.

DO NOT RUN THE POWER SUPPLY WITHOUT IT!!

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

Since you have a short across the bridge rectifier the cap should be safe.
Remove the cap then check the resistance across it, and also across the terminals where you removed it.

DO NOT RUN THE POWER SUPPLY WITHOUT IT!!

my meter does not have the specific capacitor test mode..

would i just use the (200) ohm setting? if so

it measures 0.8 on that scale

[budm]

Re: Toshiba 42HL67US blows fuses.

"it measures 0.8 on that scale: reading at the cap terminals off the board or at the pads on the board with the cap removed?
If at the pads of the board, then more likely to have shorted MOSFETs, the bad part is that when MOSFETs blew up, it can can take out the IC that drives the Gate circuits.
You will be doing some surface mounted components replacement.
You may want to look for new board at this point.

[tom66]

Re: Toshiba 42HL67US blows fuses.

Yep, 200 ohm, as before, but it must be out of circuit. Is that out of circuit?

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

"it measures 0.8 on that scale: reading at the cap terminals off the board or at the pads on the board?
If at the pads of the board, then more likely to have shorted MOSFETs, the bad part is that when MOSFETs blew up, it can can take out the IC that drives the Gate circuits.
You will be doing some surface mounted components replacement.
You may want to look for new board at this point.

i did not remove from the board yet.. wil do next.. sorry new to all of this

will post results soon

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

got the suspected cap out

tested with black lead on the Neg term of cap and red on other

at 200ohm.. 0.8

no reading when in dc volts

[tom66]

Re: Toshiba 42HL67US blows fuses.

Very, very bad capacitor, dead shorted. Now, where the capacitor used to go, check the resistance across the two open holes.

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

Very, very bad capacitor, dead shorted. Now, where the capacitor used to go, check the resistance across the two open holes.

in the (200) ohm i get no reading no matter which probe i use

at 200k only reading i get in 140.1

[tom66]

Re: Toshiba 42HL67US blows fuses.

It's probably just that cap then. The only way I can see it failing is a significant and prolonged mains over-voltage -- did you have an open neutral failure or power surge recently? If the TV got 230V (325V rectified) instead of 115V (162V rectified) then the cap would blow up very quickly. Hopefully it did not turn on and cause damage to the rest, but it looks like the damage is just at that cap.

Measure the dimensions of the capacitor and tell us so we can help you select a replacement. Replacement will hopefully fix TV.

[wickedwill]

Re: Toshiba 42HL67US blows fuses.

this is my dads tv.. he said that what happened...

power failed.. then his generator came on.. tv worked.

when power came back and generator powered down and house power(ac?) came up tv stopped workin.. that is all i had to go by

it is 200v 560 uF and i do not have a way to measure.. but.. it is about the size of a quarter in diameter.

other number on it.. KMQ 77s108? nippon chemi? 105 degrees

found tape measure.. 2.5 cm tall NOT including legs..8.5 cm diam.