Hi Brian,
I think rust was a generic term intended to mean corrosion.
However, just for an exercise, take a magnet and a selection of transistors and
diodes and you will find you can actually pick some of these devices up. I
discovered this when I found a diode hanging off of my magnetic screw
driver.
Over the years, salts in the tinning used on these leads will
leach out and react with the wire and solder causing corrosion and failed joints. A joint can look perfectly OK but you
can put your Ohmmeter on the wire of a diode and get an open circuit at the next
connection point on the card.
This leaching can also spread and destroy thin circuit
tracks,reducing them to the texture of lace curtains and causing a high
resistance or open circuit. I hope this helps.
JohnB
----- Original Message -----From: Brian DaviesSent: Thursday, January 26, 2006 9:46 PMSubject: RE: [vintagesynthrepair] Roland RD-300S troubleIm a bit puzzled and no one else seems to have picked up on this, solder cannot rust it has no iron in it! So just what do you mean by the solder has rust on it? Note also that the PCB tracks are made of copper and they are either tin plated of solder plated or varnished so again they do not contain iron ergo they also cannot rust.