TO: ALL WOOD COUNTY EMERGENCY COMMUNICATIONS AMATEURS
ALL NON-WOOD COUNTY EMERGENCY COMMUNICATIONS AMATEURS
FROM: KEN HARRIS WA8LLM
WOOD COUNTY EMERGENCY COMMUNICATIONS INCORPORATED
WV ARES BULLETIN NR 13.16 DATE: April 21, 2013 SUBJECT: A LITTLE HEAT CAN TELL A LOT
In the world of electronics, heat can tell a lot. Where does heat come from? It is generated when electric current passes through a resistive path. You may want heat in some places when working with electronics, and not want it in others.
In the days when vacuum tubes were being used, heat was needed to cause the electrons to be removed from the cathode element of a tube and passed through a vacuum, to be collected by the plate of the tube. In the process of moving from the cathode to the plate, the electrons could be controlled and the vacuum tube could be used for different jobs.
In some radio circuits heat is used to keep the frequency of a crystal at a constant temperature, which would keep the radio on an exact frequency.
Where you don't want heat being generated is in batteries, motors, transformers, and fuses. When heat is being generated by these devices, it's an indication something may be wrong.
If a fuse is getting warm, it could be the fuse is reaching its maximum current carrying limit and may be getting ready to blow. It could also mean the fuse doesn't have a good connection in its holder, and the heat will cause the fuse to become defective.
In a battery, it's an indication that too much current is passing through it and may have a shorted cell. If this is the case, the battery will be of no use when it's needed, and may cause other batteries in the system to discharge faster. It can also cause the charging device to break down or become defective.
In motors and transformers there's always some heat being generated due to the design and nature of them. A good rule of thumb for motors and transformers is, if you can put your hand on it for an extended period of time without having to remove it, it's probably running normal.
On fuses and batteries, there should be no heat at all. If there are several batteries in your system, feel each of them and compare the difference. If one is warmer than the rest, that battery should be replaced.
If a fuse is warmer than it should be, check to see how much current is going through that circuit, and make sure the fuse has a good connection in it's holder.
Ken Harris WA8LLM
WCEC
Wood County WV