# old us amps



## JHUSTON (Jun 19, 2014)

Hello I have a 250c amp. It was working and once I reinstalled in new heatsink now not working. One quick deal I noticed is I show 13v on primary side of transformer but no voltage on secondary. What makes the voltage on secondary or why would there not be voltage there?

Tthx in advance


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## ATOMICTECH62 (Jan 24, 2009)

The mosfets connected to the primary windings have to be switching on & off to create the AC needed to induce the voltage in the secondary.


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## JHUSTON (Jun 19, 2014)

Hello, I tested all the power MOSFETs and they tstes good. They all have 13.8v with power on. One out leg has nothing and other has either1.5 v or .15 can't remember. Also a smaller toroid has a diode in the center that peaks my curiosity. This is such a weird deal as the alp worked before dissassebly. Regardless I will add pic of power supply and that diode. Any help is much appreciated. I just am not sure where to go


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## JHUSTON (Jun 19, 2014)

I know its in bad shape but I'd like to get it working. I've redone the heatsink. Last pic of board bottom


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## TrickyRicky (Apr 5, 2009)

The B+ filter caps look a bit weird...why would they be facing different ways? Most amps keep all the caps negative side facing the same way. I tried looking up US Amps pics online to see if this is normal but no luck.


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## Dawgless (Oct 6, 2014)

TrickyRicky said:


> The B+ filter caps look a bit weird...why would they be facing different ways? Most amps keep all the caps negative side facing the same way. I tried looking up US Amps pics online to see if this is normal but no luck.


What TrickyRucky said.  All the US Amps that I have, basically the two I bought off of you, the negative poles all face the same direction. Make sure to check the board for polarity to ensure they're all in the same direction.


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## vwguy383 (Dec 4, 2008)

Lets see a picture of the redone heat sink! You were the one that said you could anodize heat sinks?


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## AR15corvette (Jan 13, 2015)

nice old school amp


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## JHUSTON (Jun 19, 2014)

AR15corvette said:


> nice old school amp



Want to buy it?? Lol, its for sale


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## JHUSTON (Jun 19, 2014)

Heatsink


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