Hey all, been awhile for me since I've been here. Anyway, I just bought this really really old Pyramid PB-251 for $20, figured an actual amp would be better then my head unit. So I got it to tide me over till I can get another beast Audiobahn amp.
When I turn the car on it's like a hiss/buzz/squeal kinda mix sound coming from all four of my Polk's. I just went out and unplugged the rca's and the buzzing stopped. So would it be coming from the rca or just the a bad amp?
I did just pull out a car amp I had hooked up and there wasn't any buzzing... so that kinda throws out the rca's which I did just buy.
OOO, any ideas what could cause this inside the amp? I could just take it apart and replace some stuff, since it is old, new stuff would hurt it. I only need it till I get that Audiobahn, but that's $250+ from now so could be a little while, no job and all yet.
Any ideas would be helpful, on the bright side though, if I could get rid of the buzzing, then I could sell it for $25, that's makin a nice little profit and 10% of what i actually need... Haha
Replies (2)
swez on 06/30/2004 22:12:12
Get a Walkman with RCA patch cords on 1 end and the 3.5 mm headphone jack on the other. Plug that into your amp inputs and see if the problem is still there.
If no buzzing, you have a signal problem from your HU to that amp.Try turning up the amp gains to say midpoint or closer to 4.0 volts and see if that helps. It could be a ground loop issue.
If there is still buzzing and noise, pill out the amp, open the cases and look at the PC board. The RCA jacks may just be loose and a light solder job will get you back in biz. These kinds of things happen a lot in older amps and basically, the grounds may have come loose.
Finally, look for poor solder joints on the board. A good joint is bright and shiney. A poor joint is dull grey and grainy. Can clean the board up with rubbing alcohol and a old tooth brush, then resolder poor joints with 60/40 alloy rosin core solder. A small diameter solder wire is best and if you get to heavy with solder... a copper braded wire (solder wick) will clean it up and you can resolder again. Look carefully for soldering shorts.
Finally, if this amp is really old..(10 years +) The eletrolytic filter caps in the power supply may be dried out or leaking badly. These can be replaced as well... but getting the proper value (uF) range is key. You can use a higher voltage version too. It won't hurt a thing. Just make sure you test the CAPs first with an ohnmeter, before replacing them.
Caps are good if when removed and shorted out, then apply ohmeter leads to cap. (observe polarity) If the meter goes down to near "0" ohms and then creeps back toward infinite resistance, it is probably OK. If the CAP does not move the meter at all... probably shot.
Swez
PS Good to see ya back on the board again! SMILE
accusedmonk on 07/1/2004 00:25:46
Thanks Swez. I don't know how, but for some reason after hookin it up it my house with an ac adapter and some spare 6.5's the buzzing is gone. I didn't change anything about how I hooked it up in the car, but then again I'm not complaining GRIN. That could possibly be the best $20 I've spent, well besides gas money (-.- )... But now I'm good for awhile, oh if you wanna check out my car, I have pics of the system on it, at www.beastaccord.topcities.com, If anyone has ideas for my system I'd be glad to hear em. I need to update some stuff though since I have the "new" amp and finally secured the other one down.
Again thanks.
When I turn the car on it's like a hiss/buzz/squeal kinda mix sound coming from all four of my Polk's. I just went out and unplugged the rca's and the buzzing stopped. So would it be coming from the rca or just the a bad amp?
I did just pull out a car amp I had hooked up and there wasn't any buzzing... so that kinda throws out the rca's which I did just buy.
OOO, any ideas what could cause this inside the amp? I could just take it apart and replace some stuff, since it is old, new stuff would hurt it. I only need it till I get that Audiobahn, but that's $250+ from now so could be a little while, no job and all yet.
Any ideas would be helpful, on the bright side though, if I could get rid of the buzzing, then I could sell it for $25, that's makin a nice little profit and 10% of what i actually need... Haha
Replies (2)
swez on 06/30/2004 22:12:12
Get a Walkman with RCA patch cords on 1 end and the 3.5 mm headphone jack on the other. Plug that into your amp inputs and see if the problem is still there.
If no buzzing, you have a signal problem from your HU to that amp.Try turning up the amp gains to say midpoint or closer to 4.0 volts and see if that helps. It could be a ground loop issue.
If there is still buzzing and noise, pill out the amp, open the cases and look at the PC board. The RCA jacks may just be loose and a light solder job will get you back in biz. These kinds of things happen a lot in older amps and basically, the grounds may have come loose.
Finally, look for poor solder joints on the board. A good joint is bright and shiney. A poor joint is dull grey and grainy. Can clean the board up with rubbing alcohol and a old tooth brush, then resolder poor joints with 60/40 alloy rosin core solder. A small diameter solder wire is best and if you get to heavy with solder... a copper braded wire (solder wick) will clean it up and you can resolder again. Look carefully for soldering shorts.
Finally, if this amp is really old..(10 years +) The eletrolytic filter caps in the power supply may be dried out or leaking badly. These can be replaced as well... but getting the proper value (uF) range is key. You can use a higher voltage version too. It won't hurt a thing. Just make sure you test the CAPs first with an ohnmeter, before replacing them.
Caps are good if when removed and shorted out, then apply ohmeter leads to cap. (observe polarity) If the meter goes down to near "0" ohms and then creeps back toward infinite resistance, it is probably OK. If the CAP does not move the meter at all... probably shot.
Swez
PS Good to see ya back on the board again! SMILE
accusedmonk on 07/1/2004 00:25:46
Thanks Swez. I don't know how, but for some reason after hookin it up it my house with an ac adapter and some spare 6.5's the buzzing is gone. I didn't change anything about how I hooked it up in the car, but then again I'm not complaining GRIN. That could possibly be the best $20 I've spent, well besides gas money (-.- )... But now I'm good for awhile, oh if you wanna check out my car, I have pics of the system on it, at www.beastaccord.topcities.com, If anyone has ideas for my system I'd be glad to hear em. I need to update some stuff though since I have the "new" amp and finally secured the other one down.
Again thanks.
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