[R-390] Case Comments -Long post

[Perry Sandeen]

Gentlemen,

There is no such thing as a louvered or un-louvered case that can properly cool a R390, R390/A or
SP600 without fans unless you’re outdoors at the north or south pole.

There are several problems unique to case mounting.

For the R390 the first solution to the regulator heat problem is to install the SS regulator
designed by Dr. Jerry in the HNS that has been mentioned before.  (I can’t find it in my perusal
of the index.  Someone please jump in.)  The next thing is fans.  The cheapest bang-for-the-buck
are 12 volt computer case fans.

The most common size that is sold by Newegg  is 120MM (about 4 ¾ inches.  For a little over $10 a
pop you have a choice of CFM and noise levels.  They have customer reviews that are very helpful.

I don’t have any experiences with the R390 but the following comments are relevant to the “A” and
most SP 600’s.

First the “A”. Because of it’s fold-over design it is more important to get good airflow to the
bottom than the top.  People have reported putting spacers under the audio module because of the
heat generated by the dropping resistors in the closed space.  Why no one has suggested putting
the resistors on top and the filter caps inside the audio module is a mystery to me.

On most of the SP 600’s I have there are two 20W dropping resistors underneath the power
transformer.  A SP 600 may need to have all IIRC  three power resistors remounted to the top side
in order to have reasonable temperatures underneath.

One needs to channel a lot of air under the case bottoms of each.  The “A” is easier to cool
because of the larger holes in the side as well as an empty interior  space where a small fan may
be installed. So each will require different sizes of air ducting from fans.

We must remember that the receivers first had to meet a volume and front panel specification. 
Then they had to meet performance specifications and a reparability requirement.  With the “A”
especially, module swapping could be done fairly rapidly by not very skilled techs.  Receivers
could be turned around faster.  If  module swapping or techs that joined the AF to avoid the army
in Viet Nam and weren’t good at troubleshooting didn’t fix at Karmursel AS (A huge intercept base
near Istanbul), they trashed them out.

There was never, ever any specification for receivers to last 25 years or longer.

Regards,

Perrier



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