AMP. PROBLEM PLEASE HELP!

[Stellasstillarat]

Im using a no name 500 watt 35 amp 12 volt combo amplifier. Its a base amp and is the same as the 500 elet Palomar. It works quite well besides one annoying problem. When it's first turned on all I hear is the fan. The fan is actually quite quiet and does the job of keeping the amp nice and cool. Here's the problem after the amp is running for about 1-2 minutes an annoying buzz develops. It sounds much like a battery charger when you first start charging a dead car battery. like a power draw noies. Unlike a battery charger that stops buzzing when the battery is sufficiently charged the buzzing in the amp doesn't stop. It doesn't matter whether the amp is in low med or hight. The wattage seems correct and the pre amp works. I use the 12 volt built-in power supply to light my three window meter. The built-in power supply also works well lighting the Windows on the meter. I've done nothing to try to correct the problem. I thought of spaying the fan motor but I have little to no experience with any type of electronics and don't want to make things worse. So my friend's what should I do? If there's anything I can do to pinpoint the problem please let me know and I will do my best. If you know what the problem is through past experience with this type of buzzing amp noise, Please tell me what to do to correct the problem. It's a shame because besides that buzzing the amp is doing a fine job but I can't continue using it with the buzzing. Im a stickler for excellent audio and the buzz isn't only annoying me but if i leave the audio turned up to where reports are loud and clear the mic picks up the buzzing, causing me to have to turn down the Mic and not getting the max audio out of my radio and mic. Another thing I should mention is that when i shut down the amp the noise emedietly stops eventhough the fan continues to spin for about 5 seconds then comes to a stop. HELP ME! Thanks again my friends.

 

[9C1Driver]

Are you saying this noise is comming from the fan itself? Is this sound something you hear but when you transmit the people on the air cannot hear the sound? Or is the humm comming from inside the amp?

 

[Captain Kilowatt]

I would start by tightening down every screw I could find starting on the inside of the power suppy section. It may be just a loose panel or screw.

 

[Stellasstillarat]

Correct the people cannot hear it. The only way others can hear it is the buzz getting picked up through my mic, when the Mic is turned up. I don't want to confuse you thay hear it like someone hears a tv it's getting transmitted as back round noise. TE="9C1Driver, post: 497023, member: 7716"]Are you saying this noise is comming from the fan itself? Is this sound something you hear but when you transmit the people on the air cannot hear the sound? Or is the humm comming from inside the amp?[/QUOTE]
Corr

 

[Radioman1]

If it were me, I would power down the amp, open the case, disconnect the fan and turn it back on, would not transmit and see if the noise came from the fan itself, in other words isolate the problem, sounds like to me the fan needs some lubrication or replacement.....my best guess.....

 

[Stellasstillarat]

Captain it sounds a lot like n electronic buzz. I don't think it's a lose internal item vibrating. The strange thing is, is that it's quiet until it heats up for a couple of minutes the the buzz gets louder and louder as the amp runs. It eventually levels off to a fairly loud buzz. OTE="Captain Kilowatt, post: 497024, member: 39"]I would start by tightening down every screw I could find starting on the inside of the power suppy section. It may be just a loose panel or screw.[/QUOTE]
Cap

 

[Captain Kilowatt]

I'd still try it. As it warms up metal expands. It could even be the plates of the power transformer buzzing. Make sure the thru bolts holding the laminations of the transformer together are tight. Once upon a time I rewound a transformer to get the voltage I wanted and when I put it back together some of the plates were loose and it buzzed like a bee hive until I torqued the bolts really tight.

 

[Stellasstillarat]

Captain that sounds like a good idea. It makes a lot of sense. Do you think that lose transformer screws would make the transformer buzz after warm up, as the buzz gets louder as time goes by then once it reaches a sertain buzz level it prity much stays at that levle. I will get a friend to help me do exacly what you suggested. Thanks so much capain. I will let you know how it went.UOTE="Captain Kilowatt, post: 497035, member: 39"]I'd still try it. As it warms up metal expands. It could even be the plates of the power transformer buzzing. Make sure the thru bolts holding the laminations of the transformer together are tight. Once upon a time I rewound a transformer to get the voltage I wanted and when I put it back together some of the plates were loose and it buzzed like a bee hive until I torqued the bolts really tight.[/QUOTE]
Ca

 

[vkrules]

Sounds like you are describing ac hum .Check the transformer as CK said tighten everything down. If it is the laminations (very common) and you cant get them tight ,put some lacquer or a few drops of glue on them.If it is the fan remove the sticker across the back and put a few drops of oil on the shaft and bearing.And clean the blades while you have it apart.