Anth's Computer Cave

Try your luck at TV repair

A faulty Hisense TV. Picture: Anthony Hartup.
A faulty Hisense TV.

I recycle old junk as part of the teardown series in the Cave, but before I demolish appliances for their parts I make sure there is no way to repair them. After all, the best recycling method is to re-use the appliance in its original form.

I've tried my hand at fixing TVs a few times, with little success, but I was quietly confident when I saw the symptoms displayed by the latest potential teardown.

The symptoms

This 22inch Hisense TV would not fully power on. The power light would glow red, then blue, and there was a faint flickering on screen. After about five seconds the unit would power off. It would repeat this behaviour every time you switched it on.

During a previous attempt at fixing a plasma TV years ago I had heard this behaviour was commonly caused by faulty capacitors, so I had my fingers crossed.

The TV with the rear panel removed. Picture: Anthony Hartup
The TV with the rear panel removed.

As soon as I removed the rear panel I knew I was in luck.

You can see the power supply(PSU) in the top-left of the image above.

The PSU from the TV with four blown capacitors. Picture: Anthony Hartup
The PSU from the TV with four blown capacitors.

Four of the output capcitors are bulging, with three of them leaking black ooze.

A close up image of four faulty capacitors in a TV. Picture: Anthony Hartup

At this stage I did not know if the capacitors were the only problem, or whether they were a symptom of a larger problem.

The underside of the TV PSU showing the position of the capacitor pins. Picture: Anthony Hartup
The position of the capacitors underneath the circuit board.

The traces under the circuit board were well-spaced, so we thought we'd have a go at replacing the caps.

The circuit board with a black substance leaked from the capacitors. Picture: Anthony Hartup

Once we removed the old capacitors we could see they had also been leaking from underneath.

The four faulty caps were identical 25V 470uf units.

I went through my kit of salvage parts and found an odd-bod collection of four suitable capacitors. Two were 470uf and the other two were 1000uf, and all were at-least 25V.

It would have been nice to have a matched set, but I'm not trying to be fancy, here, I'm trying to be cheap. You can't get much cheaper than free!

Four salvaged capacitors replacing the original blown capacitors in a TV. Picture: Anthony Hartup
My miss-matched array of salvaged capacitors.

I used the 1000uf caps(the blue and brown pair) on the input side and the 470uf pair on the output. I thought it would be better the 470uf caps draw from the larger 1000uf caps than the other way around.

We were so confident by now that we reassembled the TV and fully attached the rear panel before we even plugged it in.

The first thing we saw when we hit the switch was the Hisense logo, right where it should be.

Since then it has been running as a monitor for a desktop computer and it works perfectly. Only time will tell if the caps were the sole problem, but it's been a few days without missing a beat.

There's some cave-electronics to start your day. The solution doesn't have to be pretty, it just has to work.





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