Troubleshooting an humming WOPL : need help!

There's less noise with the amp alone (I guess, bescause now I'm a bit lost...) or with the amp connected to the mixer (never tested before)
There's more noise with the amp connected to the preamp thant before.
 
I would guess your pre amp is noisy...possibly the mixer too. Could you take the amp to pre-amp RCA cables and leave them plugged into the amp , un[plug them from the pre-amp and then short the ends of the RCA cable by taking a small wire wrapped around the middle prong and then to the ground shell of the cable?? What we are trying to do with that is eliminate any influence of the source...
 
laatsch55 said:
I would guess your pre amp is noisy...possibly the mixer too. Could you take the amp to pre-amp RCA cables and leave them plugged into the amp , un[plug them from the pre-amp and then short the ends of the RCA cable by taking a small wire wrapped around the middle prong and then to the ground shell of the cable?? What we are trying to do with that is eliminate any influence of the source...
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You mean shorting Left Right channels or shorting each channel with its ground?
 
Coldsmoke said:
You mean shorting Left Right channels or shorting each channel with its ground?
Click to expand...

Short each channel with it's ground. Short the left input center conductor to ground and short the right input center conductor to ground.
 
Sorry guys it's almost 5:30 in the morning here, I feel a bit tired :toothy5:
Thanks A LOT by the way for your patience and incomparable help
 
I think I'll leave it here for today, MANY thanks for your valuable help again : I feel we've made some progress here (that leaves me by the way with a shi*** p-amp...
I can't understand how that unit was working so well at salers place and so bad here :/

Talk to you soon I guess :D
 
I'll be here all day tomorrow.....or today for you I guess....
 
try different RCA cables if you have not yet. The thing about the shields being cut makes me wonder if that is the problem. A different set would be a simple enough test.
 
I also noticed on your Bridge Rectifier you have no snubbing capacitors.. A .01uf / 400 volt polypro or mylar caps accross all 4 lugs will help a bunch. This could be the source of the remaining hum....
 
laatsch55 said:
I also noticed on your Bridge Rectifier you have no snubbing capacitors.. A .01uf / 400 volt polypro or mylar caps accross all 4 lugs will help a bunch. This could be the source of the remaining hum....
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Hello laatsch,
I've been earing to my amp today and I can say that it's MUCH better than it was before (confirmed by the second pair of ears that I've at home, meaning my girfriend's)
I've been trying to look around for the snubbing capacitors : I noticed you advise to put these in place in case of increase of the power caps values, but I'm not sure how these are supposed to be mounted... Can you give me a tip?
Btw, I gave an eye to the PL2000 service manual and I suspect all the diodes (Z1, Z2, Z3) and maybe Q1 to be a little tired... I'll try to source new parts and tell you about it.
 
I don't advise putting these in place because of increased power supply cap values, but rather to cut down.on the switching noise if the diodes within the bridge rectifiers. One cap between each two post combination on the BR. 4 total...
 
laatsch55 said:
I don't advise putting these in place because of increased power supply cap values, but rather to cut down.on the switching noise if the diodes within the bridge rectifiers. One cap between each two post combination on the BR. 4 total...
Click to expand...

ok, I have it, one cap in parallel with each diode. Please pardon my naive questions, I am trying to learn in the mean time : )
 
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