- Apr 5, 2020
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I just made a modification to a ham radio (https://na8y.blogspot.com/2012/06/y...nt.html?sc=1716831031405#c7401363641202982420) and replaced a 2-watt resistor with a 30-watt power resistor (http://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=PWR221T-30-8R20F). The radio manufacturer made a design flaw, and the 2-watt resistor is known for getting too hot and cooking the board. Another ham radio operator analyzed the circuit board and determined that the resistor should be able to dissipate a little over 5 watts.
In this modification, the 30-watt resistor is mounted to the cabinet, and uses the cabinet as the heat sink. 30 watts is overkill, but doesn't seem to hurt, and this stops the radio from having a meltdown (it is known as the Chernobyl resistor).
After I completed the modification, I read that this type of resistor should have thermal paste applied before it is attached to the heat sink (that wasn't mentioned in any of the modification instructions online, of which there are several). Considering that I need at most a 7-watt resistor and that this resistor has far more surface area than the previous 2-watt resistor, do I need to buy some heat sink compound, or will I get enough heat transfer without opening the radio up again and applying it to the connection point with the cabinet?
(Every time you open it up, there is a risk of breaking a lead or doing some damage, so I try to minimize opening these up (total time would be about an hour to open it, apply the paste and close it).
In this modification, the 30-watt resistor is mounted to the cabinet, and uses the cabinet as the heat sink. 30 watts is overkill, but doesn't seem to hurt, and this stops the radio from having a meltdown (it is known as the Chernobyl resistor).
After I completed the modification, I read that this type of resistor should have thermal paste applied before it is attached to the heat sink (that wasn't mentioned in any of the modification instructions online, of which there are several). Considering that I need at most a 7-watt resistor and that this resistor has far more surface area than the previous 2-watt resistor, do I need to buy some heat sink compound, or will I get enough heat transfer without opening the radio up again and applying it to the connection point with the cabinet?
(Every time you open it up, there is a risk of breaking a lead or doing some damage, so I try to minimize opening these up (total time would be about an hour to open it, apply the paste and close it).
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