Amp noise.

Long time no lurk...


I've got an old Marantz amp in a second system. I really get remember the model just now, but anyhow...

When I switch it on I get a loud mains type Buzz noise through the speakers (With volume at zero).

Anybody got any ideas on what's causing this? I'm thinking maybe an earthing issue.

Thanks!

 

im no engineer but the last time i encountered this it was the capacitors failing?
i may be wrong but worth looking into.

 

Could be the place to start ....the shelf life of caps is suprisingly short ! approx 10 - 15 years depending on the temperature the gears been used at.....as most amps get hot etc.

 

Yeah I wondered about the caps.

The noise is when the unit is powered up so it would fit that it's the exact time that they are charging up.

Anyone know of a good supplier? I'll take a look for the model and make on the weekend and I can just swap them out with a new set.

Thanks guys.

 

caps, dry joint, earthing, cabling, mains, transformer, positioning ie coupling

 

Really any caps supplied by the likes of RS Comps are good enough. Just get the voltage right, you can increase the capacitance but I wouldn't decrease it. Just make sure you have enough room to get them in as simliar specs vary in size from different manufacturers. Normally PSU components are not PCB mounted. They are normally mounted in clamps. If they don't fit the clamps I would glue them in, as modern day structural adhesives would be just as strong and permanent.

That would be first place to start after wiggling all the wires to see if any are loose or any solder joint are cracking.

Richard

Ah! afterthought, if the caps are breaking down quite often they weep fluid. This fluid (called electrolite) is very corrosive. If they have weeped make sure you use a strong spirit based cleaner to remove it and dont lick your fingers as it is toxic.

 

Oh and also make sure you wire them the right way around as they can explode quite spectacularly on reverse voltage. Then you get smothered in bits of paper and sticky electrolite. I have known people to have serious injury from this mistake.