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Vintage threads from the first ten years
Bias pot in a 5150 ...
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 4/26/2003 9:07 PM |
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| J Payant | Bias pot in a 5150 ... Hi, I want to install a bias pot in a 5150 but the pcb is soldered up-side down to the tube sockets who are riveted on the frame... so I can't really see what's going on under. Probably some of you guys did it before and remember where to put the it. |
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| 4/26/2003 11:11 PM |
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bosephus |
time to break out the old drill!!!!! i hope other here can help you w this. i havent had the opportunity to hack one up yet... bosephus |
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| 4/27/2003 7:56 PM |
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| Joe N. |
The bias section in the 5150 is on the main board. You should see three 10uf/100v caps. towards the upper left side of the board if you are looking at it with the front end towards you. there is a 15K resistor going to ground. Remove it. Get a 25KL pot. Solder a 1K resistor to one of the outside lugs of the pot(it doesn't matter which one). and insert the other end of the resistor to ground. (the hole where you removed the 15K will work). Now solder a wire to the wiper lug of the pot, and insert it to the the other hole where that 15K was removed (it should be the one connecting to bias filtration). Leave the other outside lug of the pot alone, and you should have it. Joe N. |
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| 4/28/2003 6:37 AM |
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| Enzo |
The power tubes are not involved, so there is no reason to dismount them. I mount the bias pot in the same spot Peavey uses in the 5150-2, on the chassis right next to the transformer. Joe pretty much described the procedure. I use different values, but so what. |
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