06-16-2011, 05:53 AM
Safety caps weren't being manufactured in mid-late 1936 when the 37-89 was first manufactured, so radio set manufacturers had to use regular caps instead.
The problem is, when a regular paper capacitor fails, it may fail "open" (it opens up internally, as if there is no longer a cap there), or it may fail "short" (it shorts out and acts as a conductor).
If a cap is connected across the AC line, or if two of these are connected between each side of the line and ground (as in the case of the 37-89 and many hundreds of other Philco models), if a regular cap fails and shorts out, you have a potentially dangerous situation.
Safety caps are designed to fail open only.
I have to admit that I, too, resisted adopting the use of these for a long time, until I realized the benefit of them as opposed to the risk.
The problem is, when a regular paper capacitor fails, it may fail "open" (it opens up internally, as if there is no longer a cap there), or it may fail "short" (it shorts out and acts as a conductor).
If a cap is connected across the AC line, or if two of these are connected between each side of the line and ground (as in the case of the 37-89 and many hundreds of other Philco models), if a regular cap fails and shorts out, you have a potentially dangerous situation.
Safety caps are designed to fail open only.
I have to admit that I, too, resisted adopting the use of these for a long time, until I realized the benefit of them as opposed to the risk.
--
Ron Ramirez
Ferdinand IN
