Thanks for the response! So even though the lamp does come on at first and the picture quality looks ok (albeit just for 20 seconds), it could still be the lamp causing the problem?
So it's possible to have a lamp that is functional enough to turn on initially, but not enough to stay on?
Sorry if this is a stupid question. I just assumed that it would be like any other bulb, and when it goes bad, it won't light up at all.
The problem you mentioned can have one of the following possibilities:
3) Power Supply
In Samsung televisions if there is no picture coming up (i.e. lamp does not ignite) then the audio will turn off too. Now to diagnose the TV, the first bet is always on lamp which is almost as issue with this kind of problem.
You can also try to check the condition of a lamp by physically looking at the lamp. Look at the top edge joint where a wire from outside is connected. If you find some white fuzz around that, then most likely it’s a lamp. This is one of the ways to detect if lamp is bad.
If it does not solve your problem then I believe it’s a power supply issue since you already tried to replace the ballast.
I would recommend replacing the lamp, which seems to be most economical option too. Hopefully it should solve your problem but even if it does not you can have a spare lamp which you will need it for sure looking at your tv usage.You find the original lamp at very cheap price here:Samsung HLS6187WX/XAA Lamp
Please note the original lamp for this model is Philips. Do not buy other lamp brand which may cause other TV part go bad.
I hope it helps. Let us know how it goes or if you have any other questions or comments.