LG 22LD350 Lightning Strike

[dkneyle]

Many electrical devices in the vicinity killed by a nearby lightning strike. This small TV is dead. I'm looking at the power supply. No obvious signs of damage. Fuse is in-tact. Bridge recifier looks OK. I'm now assuming the 3BR1565JF SMPS regulator might be fried.

What usually dies when over-voltage comes down the line? I'm assuming (maybe incorrectly) that the electrical isolation of the secondary side protects most components on that side.

I know I'm lazy asking first before doing too much in the way of diagnosis, but thought that all you experts out there might have a quick answer before I fire up the soldering iron.

[budm]

Re: LG 22LD350 Lightning Strike

The surge may come through the cable connection, the HDMI, etc.
Without see the whole backside of the TV to see all the boards and how they are connected together, pictures of the boards, etc. will be hard to tell.
There should be MOV or surge protection devices on the primary side.

[dkneyle]

Re: LG 22LD350 Lightning Strike

Yes, those devices are there and seem to check out OK. It seems that induced ground voltages took out quite a few telco devices, e.g. modem and and an ethernet router that had underground cables connected to it. Most other TVs in the house survived. Two telephone handsets connected via underground cabling to a small PBX died. I think I can salvage a SMPS reg from another old board and I'll see if that gets it going. Otherwise it's probabaly a write off being such a cheap TV.

[Ltank]

Re: LG 22LD350 Lightning Strike

From my experience, surges normally take out the HDMI and or the primary section of the S.M.P.S. check fuse, diodes etc.

[dkneyle]

Re: LG 22LD350 Lightning Strike

Yep - Ltank got it right and I was going down that pathway anyway. Primary side of the SMPS. Relaced the 3BR1565JF SMPS regulator which was short and then had to do some more reverse engineering of the board to find a fusible resistor in the drain leg of the SMPS regulator was open circuit. Not had experience with these before. A non-descript looking device with F 3 stamped on it, which I assume means 3 amps. The screenprinting actually refers to it as a resistor part number. Not having such a replacement on hand I just replaced it with a link.
So another one goes back into service that was destined for the junk heap. And hopefully someone else might gain some quick answer if they have a similar fault in the future.
Case Closed!