[Amps] GS-35b heat sink

[Ian White GM3SEK]

Paul Whatton wrote:
>I remember a conversation with Ian GM3SEK about heatsinks when I was 
>building my GI7b & GS31 2m amplifiers (apologies if I misquote you Ian, 
>you'll probably pop up and say something). I also suggested heat sink 
>compound but Ian pointed out that the tube-heatsink interface 
>temperature was too high.
>

That may not be true of modern high-performance heat sink compounds... 
but the second point below is the more important one:

>He did suggest that the machining on the tube anode & heatsink were not 
>great and that it might be a good idea to stick them in a lathe and 
>skim them to improve heat transfer. I didn't actually do this but it 
>seems a good idea to me.
>
The poor surface finish of the GS35/GS31/GI7 metalwork is sure to be the 
greatest barrier against efficient heat transfer between the tube and 
its anode cooler. As we know from high-power RF transistors, the aim is 
to make the contacting surfaces so smooth that they *almost* don't need 
heatsink paste at all. Then apply the paste as thinly as possible (a CPU 
cooler is a very good example of how *little* heat sink paste is 
actually needed).

The sand-cast anode coolers on the GS31 and GI7 can't be very efficient 
either, because of the small number of fins. One option might be to 
replace these with US-style coolers salvaged from dead 8877s and 
3CX800s. It should be possible to shrink fit a solid copper plug inside 
of the cooler, with a fixing hole through the centre and a turned flange 
to mate onto the Russian tube.  (Just an idea; I haven't tried it.)


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek