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Can both IRF 510s be mounted to one heatsink if mica insulators are used? I’m thinking about doing a separate 24v supply to the finals.
John N4HNO?

Every radio I have ever looked at used one heatsink for the amp. The 50 watt FET amp that won the QST challenge did too. I’m not planning on pulling the fets off the board and mounting it far remote. ?I think it will work but wondered if any problems came up. I didn’t find any heatsinks suitable at the hamfest yesterday anyway. I was thinking of making a tiny Manhattan board and mounting it flush against ?the main pcb to mount the IRF 510s on for easy replacement. Sort of a trace extension. Tack the 510s to it so they are easy to change and repeat soldering won’t lift the traces on the main board. A board just big enough for three narrow lands with a piece of bare wire maybe 1/8” long to connect to the main board and have it butted against it to keep it as short as possible. It might work and it would help keep the repeated soldering heat off the main pcb. The heatsink would have other physical support. I might try two using old cpu heatsinks since they are easy and probably have some around. It doesn’t have to be one big one. Just an idea.
John

Hi,

Any extra lead length on the finals is too much.? The actual recommendation is to cut the leads short and mount the device even closer to the current PCB.? If you look at any PA design, they work hard to make the leads as short as possible, usually by having the heatsink directly under the PCB so that the leads can be as short as possible.? Here is the original IRF510 amp PCB:



73.

Thanks for the info.? I have a lot to learn.
-John