This has been documented plenty of times across the web, but I recently had cause to make a small modification to mine, which necessitated the lid coming off. A perfect opportunity then to take a photo and post it on the website. I built this one back in 2019 and it made a noticeable difference to my noise levels, as well as giving peace of mind that I was doing the right thing.
What modification did I make? I just replaced the 4-gang strip hanging off the output with a Belkin surge-protected item - the BSV400.
You can get all the details, component list and theory at Ian's website here: https://gm3sek.com/2019/10/11/clean-up-your-shack-2019.
Berni M0XYF
Update
I've had some feedback from Adrian M0TCD, which was enlightening and useful:
"I don't like the way the input and output leads run so close together in your mains filter as it could allow interference to cross between them. You could put the filter on the left and the fair-rite on the right to overcome this."
Which, after checking against the original design, is a mistake on my part, so I'll be fixing that sometime in the near future!