LG 42LG3000-ZA repair, doesn’t tune Digital TV, fixed

[Chungalin]

This 2008 LCD TV doesn't tune digital TV channels, but customer says that it eventually worked after heating up. This delay got longer and longer until it became unusable.

I suspect of TDFV-G135D tuner (flat encephalogram mode). I replace it and problem doesn't improve. I try to heat Main PCB with heat gun and eventually DTV comes and goes when I heat certain SMD caps. Check ESR and many of them are really high, specially 100uF/16V ones. This could also be detected with oscilloscope, but I didn't try first. Voltages show up blurry, with high frequency noise, instead of a sharp line. I replace all 100uF/16V SMD caps related to regulators for +1.8V_TU, +3.3V_TU and +5V_TU (see available schematic at ET for registred users), and it works again even from cold state.

I've seen this same problem in LG DVD recorders from same production year. These SMD caps are aging fast and will cause a lot of trouble. They're hard to remove without damaging tracks.

[Braderz]

Re: LG 42LG3000-ZA repair, doesn't tune Digital TV, fixed

I have never looked into the respective components your post concerns, but what I will say is that this TV is one that I have had the longest relationship with. I Currently have one and a half, and am stuck between creating a concept TV, with extended ribbons/cables enabling me to house everything in a separate, slightly cooler area, or just selling the boards.

If you're in the UK I am happy to send you what you need.

[Braderz]

Re: LG 42LG3000-ZA repair, doesn't tune Digital TV, fixed

I perhaps didn't read correctly.
Well Done on the repair.

[Chungalin]

Re: LG 42LG3000-ZA repair, doesn't tune Digital TV, fixed

Thanks, no problem, Braderz. I generally post solved cases.

[ducky29]

Re: LG 42LG3000-ZA repair, doesn't tune Digital TV, fixed

Good job on the repair. What tool do you use to check the esr of the caps? Do you remove them from the circuit and then test? I used those cheap esr meters you can buy on ebay, but after some time they fail and im looking for a better tool. Thanks

[Chungalin]

Re: LG 42LG3000-ZA repair, doesn't tune Digital TV, fixed

I use EVB ESR meter:

http://clientes.netvisao.pt/greenpal/evb1.htm

This one has even resisted a 230V AC accidental contact, with minimal repair.

I check first in circuit. It’s not a precise reading but at least gives a hint on suspicious elements. Impossible to remove SMD caps just for testing. Once removed, they’re gone.