Toshiba 58L4300U won't power on

[Nexus1966]

Re: Toshiba 58L4300U won't power on

Looks like D201 is a schottky also. It appears to test OK, but I only have a cheap analog meter with a 1K ohm setting, no 10K option. But I get full scale one way, nothing at all the other way. I'm assuming D201 is good.

[CapLeaker]

Re: Toshiba 58L4300U won't power on

I started just testing random components and found what looked to be a shorted diode.

D301A or D301B (they are in parallel) - a google search of the part number brought me to this: http://www.vishay.com/diodes/list/product-89144/

According to that page it is a schottky diode. I got an analog multimeter to test them with the instructions I found here: http://www.electronicrepairguide.com...tky-diode.html

One of them appears to test good, the other one is shorted both ways.

That is the power for the backlights. Change both diodes for at least 200V 3A or higher schottky. Check the Mosfet Q301.

For now, you could take the bad schottky out (the run parallel) and don't hook up the backlight. See if the 12V returns.

[Nexus1966]

Re: Toshiba 58L4300U won't power on

I found the diodes at DigiKey.

Q301 appears to be bad, at least according to the method I found on how to test with a DMM.

I removed it, shorted all the pins together, then used the diode check function on my meter with the negative on the source and the positive on the drain, I get continuity before triggering the gate.

It's part number is TK13A25, DigiKey appears to not have them. Checking around for a replacement now.

Edit - DigiKey suggests 497-12570-5-ND as a replacement.

[CapLeaker]

Re: Toshiba 58L4300U won't power on

I the Drain and or the Source pin shorted to the Gate? if it is shorted to the gate pin, then you would have to check out the gate drive circuit and the PWM too.

[Nexus1966]

Re: Toshiba 58L4300U won't power on

No, neither appears to be shorted to the gate.

[CapLeaker]

Re: Toshiba 58L4300U won't power on

good.

[Nexus1966]

Re: Toshiba 58L4300U won't power on

Does the diode and the MOSFET both being bad explain the issues, or might it be deeper than that?

[Nexus1966]

Re: Toshiba 58L4300U won't power on

My parts from Digi-Key arrived today, so I replaced the 2 diodes and the MOSFET.

Success!

[CapLeaker]

Re: Toshiba 58L4300U won't power on

perfect!

[skaterdudz02]

Re: Toshiba 58L4300U won't power on

Being new to all of this on repairing tv's, did you happen to have the part numbers for the diodes on digikey's site? I see the mosfet one, but am unsure which one to order.