Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Prime PSU Buzzing fix

Hi All,

Hope things are good with everyone. Not been able to log in for a while; lots of personal changes and only just enough time to listen to my system, never mind chat about it.

I've had a Prime + PSU for years and got pretty annoyed at the 50Hz mains buzzing from the PSU (external noise audible when the system is off from a few feet away, loud enough to hear through open back HD600s). I don't know how widespread the issue is, but on the off-chance that somebody else has it, here's the fix. I did do a search to see if it's already been spotted. Apologies if this is a dupe!

I should have sent it back for a repair years ago but never got around to it. Since it's too late now and I had a spare hour I thought I'd take a look. The buzzing is obviously from the chunky toroidal transformer inside the PSU. I was expecting to find a central nut than needed torquing when I removed the lid, but it turns out that the issue was much simpler. Primes have a very elegant way of hiding the assembly screws. There are two hidden torx screws under the Meridian logo plate on top. Those screws connect the silver aluminium top plate to a thin black steel plate beneath (which is screwed to the chassis in a similar way to steel/glass top of a G series). A couple of sticky pads add a bit of security. But you don't need to remove either plate unless curiosity gets the better of you.

The problem is very simple. Those two torx screws under the logo attach to the black steel plate and project through it. On my Prime, both hit the black disc in the centre of the transformer and coupled the hum from it into the chassis where it was radiated very effectively. By slackening off the screws, the vibration no longer connected and my Prime is blissfully silent.

So - if you have this hum: Piece of paper on top of your PSU to prevent scratches, magnet to remove black logo plate, slacken the two T10 screws beneath. No need to remove the lid itself. I did it whilst it was plugged in so that I could hear how far. If you want to fully remove the cover to take a peek inside then remove the two T10s, gently and carefully pry up one corner on the back and slide a credit card underneath, push that all the way around to release the sticky pads, then the aluminium top comes off. Next remove the 8xT10 on the black steel cover plate and you're in.

I don't know if the coupling was intentional, but in my case (maybe something else is wrong?) it was far better without. I'm thinking of sourcing some shorter screws or filing these down so that I can still get a rigid attachment for the top.

All the best,
Mark.
(who never did get that Ultima GTR finished!)

Put a washer under the screw heads?