Alchemist power supply

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adrianjones

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Joined 2010
Hi. I have purchased some quality replacement caps for the power supply of my Alchemist Pre amp(stand alone unit). I have so far changed 4 of the caps and notice that the PCB is blackened on the track side of a resistor on one channel (stereo amp) and less so on its opposite channel resistor. All these resistors measure 31/32 Ohm.
My question is, will the full replacement of all caps(16) reduce the heat being generated by the resistors, therefore, no need for concern? Or, do I need to replace the resistors?
The unit will be around 16 years old and has never been serviced before.
Thanks.
 
Mooly

Mooly

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Joined 2007
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Discolouration of PB material is normal in the presence of heat. I wouldn't worry to much if the unit is working normally. Its also far from uncommon for commercial equipment to be poorly designed with regard to heat dissipation and the suitable rating of components used.
 
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adrianjones

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Joined 2010
2 pics are attached. One of the darkened PCB and one with the new caps in place.
Many thanks for your replies.
 

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Mooly

Mooly

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The discolouration from heat is normal, but as you mentioned earlier, it is very different to the other side. One possible reason (assuming the thing is basically OK and working) could be that the heat has dried out the caps and as such the resistor is seeing more ripple voltage across it which makes it run hotter.
 
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