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SB II Final Transistor Heat Sink

n9dxp
 

Hello all,

 

I have enjoyed following the updates on the new Slop Bucket II projects. I have S/N 120 which will be used on 40 meters mostly digital modes. I have almost all of the surface mount components installed (I do them by hand). I am wondering if anyone might have any thoughts or suggestions on a more substantial heat sink for the digital modes.

 

Thanks,

 

George, N9DXP

Johnson City,TN

ajparent1/kb1gmx
 

On my  SB1 20M whch had a very similar outline and layout just different display.

I used a block of aluminum behind the final to couple it to the aluminum front panel 
in place of a spacer and an Lshaped aluminum (1" Angle alumnum) to go from
behind the irf510 to the block on the other side of the board.  The Angle aluminum
was about .1 thick. The idea was conduct the heat to the front panel (.080 aluminum)
and take advantage of the surface area.  For voice it never even got warm.   
Sorry no pictures.

For digital work the heat sink must be huge compared to the supplied one as the
full power transmit time is 100% effectively.   Voice work the average power is
under 20% often less.  Also the box must have air flow to allow heat from the final
and its larger heatsink to escape the case.  Consider using a small 40 to 60mm
fan for cooling as well. The major trick is do not make the IRF510 leads longer
or stability may be compromised. also note the tab is the drain connection so
it has the main power on it and RF so it must be insulated from any cooling
structure (it must conduct heat) and that structure must be grounded.

The IRF510 can stand up and have a block of aluminum to couple the
heat to the back  of the case.  For that I'd say a block .625"W x1"D x1"H
might do well to get to the edge of the board and couple heat to a larger
finned heatsink.   the IRF510 is mounted to the .625" wise face and the
1"x1" face to the heatsink.  Again insulating kit and ground the heatsink.

Allison

n9dxp
 

Thank you very much Allison! That it all very helpful information. Would you by any chance have a picture of your radio? Did you use a fan?

 

Thanks,

 

George

ajparent1/kb1gmx
 

I said I didn't take a picture of SB-1 and SBII is uncased and pending so I've left it stock for now.
Likely I'll do something but first I want to decide if it  will stay on 40 or move to 80 or maybe
elsewhere.

No fan, on the SB1 or likely for SBII as I really am onto into FT-8, I'd rather plant grass and
watch it grow.

Allison