Re: Heatsink issue #ubitx #homebrew

Jonas Sanamon

Hi Eduardo,

Unless You have feeding the PA with more than 13.8v, I am sure that using that aluminum plate will be enough. Remember that the heat sinks supplied by HF Signals are probaby used by a lot of uBitx owners around the world, so as long as you have a larger surface area than the original heat sinks you should be fine.  If you are using an aluminum enclosure, mount them to that and you should be fine. That also makes it easy to monitor the temperature of the heat sink, just use your hand :-)

But like I said before, you *need* to use insulating tab + plastic "washer" to isolate the IRF510s from the metal:
Jonas - SM4VEY

Den ons 14 okt. 2020 kl 21:48 skrev edoardo marchetti <mentorade@...>:

Thanks for replying so quickly, I m wondering if the only 15 x 10 cm x 1 mm thick aluminium sheet could dissipate enough power. If my option was too much heavy for the 10 watt output maybe the direct connection of both transistors to the aluminium enclosure could be a sufficient solution.
What do you think about it?

On Wed, 14 Oct 2020, 16:16 Jonas Sanamon, <sanamon@...> wrote:
Hi Edoardo,

No, I don't think You can do that without creating instability or other issues for the PA stage. 
I would do either
1) Use just one of the 2 heatsinks (which ought to be enough anyway unless You are feeding the PA with 30v and using it for WSPR or FT8). Use a FAN running very low speed (= no noise) if necessary.
2) Get a bigger heatsink.

Either way: You *MUST* isolate the IRF510s from the heat sink electrically, otherwise the smoke will come out...
(Hint: use special TO-220 isolation pads)

Jonas - SM4VEY

Hälsningar, Jonas

Den ons 14 okt. 2020 kl 15:54 skrev edoardo marchetti <mentorade@...>:
Hi everybody!
I am near to finish the enclosure of my v5 ubitx and I projected to add 2 new heatsink. The problem is that one of the mosfets is exactly on the pcb center and this forbid me in drilling a hole for the transistor mounting. 
The question is, can I desolde the two mosfets and connect a little piece of cable in order to put theme in a better position without create electrical problem? I would like to stack both at the center of the two heatsink.
Thanks for reading

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