This is a how to ????

[tvmanjon]

I have a circuit board that has 2 zener diodes that overheat and upping their wattage helps the reliability issue but I want to go one better.Id like to remove the diodes and put them on a heatsink and run wires back to the board,My idea was to find a small case form(like whats used for a bridhge rectifier?1"square? and encapsule them in some epoxy .The problem Im having is finding the supplies.If there are any other ideas Id appreciate any.Thanks

 

[Hayato]

And if you use the zeners to drive a transistor?

 

[Hero999]

Please post the schematic.

 

[tvmanjon]

there is no available schematic...on the net or the MFG that Ive been able to find.I have drawn out that section but its crude.Im not looking to change the design just the heat disipation thats caused by the components being underrated and a 5watt is ok but a 10 watt would do great but there are none so I want to fabricate my own encapsulation I know it will work because I mocked up the concept but I want to make it look good and be able to make a number of them for a quantity of boards I service any thoughts on a concept or material supply Thanks

 

[Hero999]

Can't you scan it or take a picture of it with a digital camera?

 

[tunedwolf]

You would be far better off designing a more efficient way to control your voltage and current rather than wasting all that power into heat. Where there is is excessive heat, there is unreliability. Moving the diodes outboard to a heatsink is not really a solution in most cases, albeit it that on the face of things, it would seem to be the simplist thing to do.

 

[tvmanjon]

Thats not a option.The engineers simply underated the wattage of the zeners that were needed.The replacement boards have a upgrade of larger wattage zeners ansd solves the problem.Its no different than using a 1/4 watt resistor where a 1/2 w is needed.Im just looking for ideas on how to heat sink or encapsule the diodes.The other heat generating device is a 5w 1K resistor which is right over where the zeners are sitting on the board.The diodes when moved out of harms way run cool and work fine.thanks for the feedback

 

[Nigel Goodwin]

For a high wattage 'zener', have you considered using a power transistor to increase it's wattage?. Using a power transistor makes it easy to mount on a heatsink, and you can use a small cool running zener.

 

[Hayato]

Yes, I suggested that on my first post.

 

[tvmanjon]

Thanks for all the replies Im sure adding a power xistor would be better than the factories design but cost and time are part of the equation.Simply removing the zeners off the board and hanging on a wire harness they run very cool..If i had the smarts Id try the power xistor just to see but its not my expertise.So I did find a simple solution that involves wiring the zeners in a small circuit board and running the wires back to the main board.I located the thermally conductive epoxy and a mold called a "potting box" It will end up about 1"x1"x.75" and mount out of the way costing me less than a couple bucks.Jon