Tanwa or Sakis. Can either of you help? My son has a 640A and there is a buzz that comes from the speakers even when the volume control is turned town. In fact the buzz goes away if you turn the volume up? This is even without any signal or cables (other than speaker cables) plugged in.
After the 640A has been on for 30 to 45 minutes, the buzz almost disappears. I have tried cleaning all connections and pots within the unit and it did not make a difference.
The buzz has grown more prominent over the past few months.
Any help to remedy this would be so appreciated. Thanks!
After the 640A has been on for 30 to 45 minutes, the buzz almost disappears. I have tried cleaning all connections and pots within the unit and it did not make a difference.
The buzz has grown more prominent over the past few months.
Any help to remedy this would be so appreciated. Thanks!
if there is no other "outside " related factor like a fluorecent lamp inside the room or any other earthing issue ...this can only be caused by some connection of the ground inside the amp ....remote posibilty that can be alsosome capacitor issue
normally if its a connection thing has not much to do with time or rising temperature ...if its there its there nommater how much time or how hot is the amp
you need to look farther
normally if its a connection thing has not much to do with time or rising temperature ...if its there its there nommater how much time or how hot is the amp
you need to look farther
Actually, the whole problem started when my son had changed a light bulb in his room to an "energy saving" type. The buzz was extremely loud. So had changed back to the original bulb, and the buzz subsided, but not entirely. Crazy huh? Before all the bulb changing it had been entirely quiet.
I wonder if something has come loose in the light fixture itself, though the buzz is there whether the light is on or off. Hmmm.
I will keep poking around (power off of course!), work with your suggestions, and see what happens. Also haven't tried the obvious... try running it through my stereo in another room altogether.
Thanks for all the input!
I wonder if something has come loose in the light fixture itself, though the buzz is there whether the light is on or off. Hmmm.
I will keep poking around (power off of course!), work with your suggestions, and see what happens. Also haven't tried the obvious... try running it through my stereo in another room altogether.
Thanks for all the input!
This is a bit off-topic for the 740 schematic, Leviathon. Did you already start a thread for the 640? Anyways, the CFL thing should tell you something. Try again - same result? Remove 1 spkr lead at a time - listen. No change? Try all inputs same way.
That should eliminate signal, RF sensitivity. Now, mains sensitivity - try as you say in another, distant room. Try a line filter (not a simple MOV powerboard) You may have to borrow this.
Check that amp is properly wired with earth continuity if it is not actually double insulated. Check owner manual? Anyway, since you poked around inside, you would know what a green/yellow wire coming from the power inlet looked like and to what it should or should not connect. My 650T has no indication of earthing and isn't. Never try to add a mains earth connection to a double insulated appliance. A technician might test it via an X2 rated cap. If the amp is earthed, it must have the best connections in the amp. It's not a proper test but measure R from mains earth pin to chassis on multimeter low range or continuity test.
Having stayed with simple, closed box tests you are left with the likely fault areas as Sakis has outlined. They are not necessarily easy to trace, even with schematic.
That should eliminate signal, RF sensitivity. Now, mains sensitivity - try as you say in another, distant room. Try a line filter (not a simple MOV powerboard) You may have to borrow this.
Check that amp is properly wired with earth continuity if it is not actually double insulated. Check owner manual? Anyway, since you poked around inside, you would know what a green/yellow wire coming from the power inlet looked like and to what it should or should not connect. My 650T has no indication of earthing and isn't. Never try to add a mains earth connection to a double insulated appliance. A technician might test it via an X2 rated cap. If the amp is earthed, it must have the best connections in the amp. It's not a proper test but measure R from mains earth pin to chassis on multimeter low range or continuity test.
Having stayed with simple, closed box tests you are left with the likely fault areas as Sakis has outlined. They are not necessarily easy to trace, even with schematic.
Hi Ian (et el),
Yes, my apologies for going off topic. I did post on May 24th, but no replies. Sorry for not following protocol.
I will try all the suggestions, and hopefully have good news to report back.
Being a father's day weekend, and a bit rainy here as well, I hope to get a couple pieces of audio gear in my household back in order.
Thank you all,
Ed
Yes, my apologies for going off topic. I did post on May 24th, but no replies. Sorry for not following protocol.
I will try all the suggestions, and hopefully have good news to report back.
Being a father's day weekend, and a bit rainy here as well, I hope to get a couple pieces of audio gear in my household back in order.
Thank you all,
Ed
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