This isn’t so much a profound tip as an interesting story. DSL lines can be subject to different types of interference. You will probably never forget that fact after you read this story:

“A 400-resident village in Wales suffered 18 months of DSL Internet outages each morning until the culprit was identified as electrical interference from an old TV set”, according to this post on Ars Technica. Eighteen months! The service provider replaced cables and took every remedial measure that they could think of.

Finally, they resorted to walking around the village with something called a Spectrum Analyzer. The technicians recounted that they “walked up and down the village in the torrential rain at 6 am to see if we could find an “electrical noise” to support our theory. And at 7 am, like clockwork, it happened! Our device picked up a large burst of electrical interference in the village….The source of the “electrical noise” was traced to a property in the village. It turned out that at 7am every morning, the occupant would switch on their old TV which would in turn knock out broadband for the entire village.”

The embarrassed TV owner promised never to turn on that TV again. So, the story has a happy ending!