Re: KPA100 question

[john-477]

I had the same issue (there really should be a note there indicating that
you need to set the transformer back a hair to allow clearance for this later
step!).

I scooted the resistors forward a bit to solve my clearance problem. It's
always a good idea to leave a LITTLE air under power resistors, to help
them dissipate some heat. Mine stood off the board about 1/8" which was
just enough to allow
me to scoot them forward a tad, to get this cap in.

John K5MO



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[G3VVT]

 
In a message dated 23/04/05 11:55:05 GMT Daylight Time, [hidden email]  
writes:

It's  
always a good idea to leave a LITTLE air under power resistors, to help  
them dissipate some heat. Mine stood off the board about  1/8"


Reply: -----------------------------------------------
 
Can concur with that idea.
 
When I worked in TV repairs in the 1960s and PCBs first came into use,  we
used to slip a small ceramic bead over the lead to give a  small stand off to
prevent charring of the early laminated paper PCBs.  Failing this a small full
loop in the lead was made around a jewellers  screwdriver to raise the heat
generating component above the PCB, and also  provide mechanical support to the
soldered joint. Anybody who worked on these  early PCB will be well aware of
the effects that could occur. The  other problem apart from charring being when
carbonised tracking between  the layers caused an internal break down between
adjacent component leads due to  the higher tube voltages employed.
 
Latterly the method seems to be to "joggle" (kink) the component  lead to
provide a mechanical stop against the PCB and assist in component  cooling where
needed. The use of fiber glass PCB made the effect of heat  generation in the
PCB less of a problem, though should still be avoided.
 
Bob, G3VVT
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[Ron D'Eau Claire-2]

In a message dated 23/04/05 11:55:05 GMT Daylight Time, [hidden email]  
writes:

It's  
always a good idea to leave a LITTLE air under power resistors, to help  
them dissipate some heat. Mine stood off the board about  1/8"


Reply: -----------------------------------------------
 
That's what the Elecraft mod kit assembly instructions call for: "Space the
resistors about 1/16" (1.6 mm) above the PC board, and about the same
distance apart."

Ron AC7AC



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