[Icom] Re: IC756Pro - mic and cosmetics?

[George, W5YR]

Chris, as I see it, there are two forms of cooling taking place in the PRO
series. The top front vent functions as a normal vent for some radiation
and convection release of heat. But since the entire rear casting is the PA
heat sink and the internal fan must blow cool air over the devices, it
seems only logical to me that Icom would make the front top vent also the
intake vent for the fan. The fan does not seem to move as much air as the
noise level would indicate, but evidently it is enough.

When the set is cool and receiving, I can feel the slighest rise of air
*from* the front top vent showing that some radiation/convection cooling is
taking place. But, when the fan comes on, there is little doubt with my rig
that air is being drawn into the vent and passed through the set to exhaust
out the rear-panel vents.

I agree with Adam and others that the PRO really does not need any
additional cooling unless you run a 100& duty cycle mode virtually all the
time - you have to receive some of the time, you know!   <:}

If you must use a fan, I suggest that you place it at the back sucking air
from the rear vents rather than blowing it in. Does a better job and keeps
the dust out.

Chris, if I can see any daylight this week, I will comment upon your WAVES
paper. You did a lot of good work there!

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437


Chris BONDE wrote:
> 
> George:
> I think that you are the first to mention that the vent at the top is
> intake rather than exhaust.  To me that is rather a poor design, since heat
> tends to raise.  I have placed my sweaty palm above the vent and thought
> that the air was moving up out of the vent.  Even when I Tx the sensation
> was the same.  However, I took your advice and tried the Keelex text.
> 
> I used a virgin piece of Kleenx, placed it very carefully  over the vent,
> it just sat there.  Turned on Tx, still just sat there.  A ha, I was
> right.  But to be fair, I took the extra portion off the tissue so that it
> was only single ply.  (Now everyone knows what single ply does when you
> blow into it.  It opens a very nice hole from whence everything
> eminates!!)  Further, I made the size of the single py tissue the same size
> of the vent, carefully placed it over the vent and obseved.  IT DID NOT
> MOVE.  Watched again.  A ha, the tissue moved up.  Then I turned the TX
> on.  Chagrin!!  The tissue moved down into the vent.  Oh, just an
> aberation, do it again.  So I did, and so I did and so I did.
> 
> Yes, I believe that you are correct. The fan sucks the air down through the
> top vent, the vent with the hottest part closest to it, the top vent.  I,
> in my dazed understanding of convection do not understand why such would be
> so designed.  So, alas and alack, I shall go back to my design board (where
> is it?) and see if I can place the fan on the back of the rig.  Hey, that
> would be better!!  It would be out of sight and I could put my log book on
> top of the rig. ( <:+)}  )