What do you think? Fixable?

[olePigeon]

So I got a 40" Dynax (Best Buy?) TV for free, with a note that just says "won't turn on."

Opened it up and found that the huge capacitor had literally blown its top (piece of shriveled plastic), a blown fuse, and this:





Looks like I need a new one of these since the on there is literally melted:

http://www.digikey.com/product-detail/en/STR-A6059H/STR-A6059H-ND/3661840

Replace that huge capacitor, probably replace all the surrounding resistors and other bits and bobs.

Think it's fixable?

 

[Elfen]

Fixable, yes. How much it will cost? That depends on what you are willing to spend to get it fixed.

 

[olePigeon]

Well, the power circuit is $2.  The capacitor is $4.  The fuse is a couple cents, along with the other resistors.

I can get all the parts for around $10.  So I guess I'll go for it.

 

[unity]

i bet techknight would have some insight on this.

 

[wilykat]

It would help a lot if you can figure out why it blew in the first place.  It seems like something shorted out to cause those parts to burn up and blew up the cap.  I would hunt around the primary side of the power board, a major failure is almost always caused by something on primary side.  In my experience, failure on the secondary side almost never burns up like that, the circuit (via optoisolator and switching transistor) usually shut down the whole thing when there's a problem on secondary side.

 

[Elfen]

What ever that chip is, it is what went up. Question is Why?

 

[Paralel]

It could easily just need a cheap part that failed catastrophically, because Dynex uses crap parts (I can almost guarantee that)

 

[Unknown_K]

Parts are cheap enough. Could have just been a power surge or lightning strike that took it out. I would check for a direct short once you replace those parts and BEFORE you try to power it up.

You can also buy the whole power section from somebody with a working unit but cracked screen (look on ebay for that model).

 

[techknight]

That is the standby 5v circuit. It likely went when the cap went. The cap saw extreme overvoltage or possibly too high of ripple current.

You will need to change all the parts in that regulator. Diodes included.

But..... you will need to check the mosfet in the PFC boost circuit as well, it could have went out of regulation and blew the cap as well.

There are many many things that need checking. Overvoltage seems to be the cause.

It might be far easier to replace the power supply.

But you may find the mainboard dead as well.

Another scenario involves the main CPU shorting out when a surge/spike hits the HDMI. this will overload the regulator and blow up the power supply. I have seen this a few times as well. Inspect the HDMI ports for surge/blast damage. Cheaper tv sets route the HDMI directly into the processor, makimg it highly vulnerable to spikes. Older/more expensive sets use an outboard hdmi to Rgb converter IC before it goes into the processor.

I have changed dozens of those ICs, because they fail and dont take the cpu with it. But the cheaper more integrated processors do not survive.

 

[olePigeon]

:lol: Quick Google search has shown that this is an exceptionally common problem.  Cheap TV.  There're power supplies all over eBay for around $40 or even less, with free shipping.

Looks like I'll just buy a power supply instead of trying to fix this one.

 

[techknight]

Then its possible the switching regulator ic is underrated or they are using shit capacitors

 

[olePigeon]

Maybe I'll use the parts I ordered from Digikey and preemptively fix this power supply with my new parts.  Put a good IC and cap on it.

Found a power supply for $28.

 

[techknight]

Again, make sure there is no other damage to the supply or youll blow out the new parts.

 

[olePigeon]

One power supply later :

 

[Elfen]

Congrats! Its... It's Working!

 

[CC_333]

What program/film is on there? It looks like some sort of 1950's SciFi stuff (I'm guessing).

c

 

[jholt5638]

looks like mystery science theather 3000, don't know the movie they are watching though

 

[Unknown_K]

I find it is cheaper to just buy a used PS then to fix a dead one on most mass produced systems. Keep the old PS for parts, you might need it someday.

 

[olePigeon]

Mystery Science Theater 3000.  The experiment was Prince of Space.

I'll definitely hold onto the old PS supply.  I'm thinking I'll go ahead and fix it so I have an extra one for when the new one inevitably dies.