Let my main question be, "for those who have plenty of experience fixing TVs, would you recommend just swapping the fuse first?" My goals are primarily to limit any possible damage.
Absolutely not. Your TV has a severe short somewhere. Just replacing the fuse is likely to make things worse. The short is direct enough to have blown up the inrush limiter (though they usually still pass current even with a chunk missing like that, just less than they're supposed to.)
I think I have identified two bad diodes. I'm getting a resistance reading in both directions, and 1.8v measuring with leads connected backwards with my meter in diode mode. I get .523v measuring with leads connected to the proper ends. Can someone please confirm my thinking that these seem bad? They can be properly tested on the board, right?
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Thanks all. Good to know that the diodes can't be tested in circuit.
Uhhh, no...
Diodes
can often be tested in-circuit and what you have measured indicates
properly working diodes, not defective ones. In one direction, you should get the diode drop for that type of diode (about .5 volt for standard silicon,) which you are seeing, and a higher voltage in the opposite direction, which you are also seeing. Those diodes are almost certainly fine.
Maybe the relay contacts are bad and the TV has been running the main power supply through it, causing it to overheat and crack, then on the last power cycle it arced over no longer limiting inrush current and blowing the main fuse.
That doesn't make sense because the OP stated that the TV was on for about 5 minutes before it blew up, tripping the upstream circuit breaker in the process.
It is almost certainly a blown transistor (or multiple transistors.) They're usually easy to spot just by checking all the IGBTs with a multimeter since when they fail they tend to fail to a permanent hard short. The OP should be able to find the short, either the PFC transistor(s) or main PSU switching transistor(s), as you stated.
Once the shorted components have been found and replaced, power it up
ON A DIM BULB to be sure that they're not just going to blow again due to blown drivers, lack of oscillation in PWM controller, etc. If the OP can't seem to find anything shorted, they could power up with a very low wattage bulb and see where the voltage stops but I can pretty much guarantee there is a shorted transistor (or perhaps diode but unlikely in this case with such a hard short) that can be found first, without attempting a power-up.
As for the inrush limiter, it is originally a WMEC WTR15D080, so 8 ohm cold, 5A nominal max current. A Cantherm MF72-008D15 has the same specs but anything really close, like a GE CL-50 or CL-60 (7 ohm /10 ohm, 5A) or one of the Ametherm SLxx series would work fine also if you can't easily find exactly 8 ohm cold in your locale. They're typically only 20% tolerance anyway so not that critical as long as you pass enough current through it to warm it up properly in normal operation (so, for example, don't replace it with a 15A nominal model, etc. It needs to hit thermal equilibrium at around the right point, though it is very "springy".)
WMEC ICL guideCantherm ICL guideGE ICL guideAmetherm ICL product datasheet matrix