In a message dated 23/04/05 11:55:05 GMT Daylight Time, [EMAIL PROTECTED] 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 _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
