Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems noisy power amp transformer?

sometimes one of my 505s starts emitting a 50hz noise from the case. its quite soft and it comes and goes. interestingly the other 2 505s connected to the same outlet work silently.

it doesn't happen much, and when it does it lasts less than a minute.

what might cause it?

thx

Chris

Hi, I would look inside for somthing Loose.
It sounds like a resonant noise.
For Safty,Unplug it first.

If in doubt Call Meridian, it wont be the first one.

Cheers, Chris

Actually that is kinda scary advice Chris L. Unless the amplifier is left alone for a significant amount of time after shut-off, the power supply caps will still have huge (potentialy lethal) voltages stored on 'em. So the correct advice then...

A technician quickly deals with charged power supply capacitors by shorting each cap's terminals with a "bleed or drain resistor". If you don't know exactly what I'm talking about, don't even think about it!. Assuming a neophyte even wanted to pop the top and have a look-see, he should just let the amp sit unpowered for an hour or two before popping the top. As this will allow the caps to drain naturally.

FYI: Chris G, although its a mechanical noise it frequently still indicates an electrical problem. There are many intermittent faults, not the least of which is a buggy transformer, that could be creating the problem.

Happy Trails!
Vince@freewheelcycle.com

I think I'll give M a call. Thank you both.

Chris

Review this thread:

[URL=]http://www.meridianunplugged.com/ubb/ultimatebb.php?ubb=get_topic;f=6;t=001187;p=1#000010[/URL]

Mechanical Hum is quite common with power amps both my G55 and Parasound did this and also depending at what time of day, Saturdays was worst :rolleyes:

Interesting. i think the curious thing is when it happens (and it isnt often), it only affects one of my three 505s, all of which are plugged in to the same outlet.

I had this problem in an amp within the speaker. I swore up and down it was the transformer. Turned out it was a faulty load (bad solder joint) that powered the digital electronics. One drop of solder fixed it.

Although Vinces warning was good and valid don't let it scare you from taking a peak. It's probably less dangerous than opening the hood of your car while it's running. Common sense applies.

I would poke around using something like a long wooden spoon or paint stirrer while it's open and buzzing and you may get lucky it's just a tie wrap or cable vibrating against the transformer or a screw lose. If you're not the DIY handy man type then don't do it.

I work with fairly powerful lasers and 30,000 volt power supplies, those will give you a real kick pants. So I may be a little desensitized.

Nothing unusual. My 558.2 hums on saturday mornings and the 559 is completely silent. ive just got used to it but if anyone knows of a fix, i`ll try it.

My 558.2 also hums every now and again.

Edited for reasons of good taste. But you can use your imagination!

George

Too Much Informatiom Mr Meridian.