12-01-2012, 02:59 PM
Winkydink:
1. Follow Ron's advice and replace the caps first. It is simple, especially if you do not restuff the old ones and simply replace them (although with Philcos I'd restuff them to keep the appearance: it is also fairly simple with those black backelites).
2. To test a tube for gas you need a tester that tests for gas; I take it not every tube tester does it, but most Hickoks do. If you have a tester, see if it tests for gas; usually the word "gas" appears on the front panel over some buttons and in the manual.
What gas does is cause unplanned ionization (there should be no ions in a tube) radically changing tube's VA characteristics. Getter is pllaced inside tubes to bind residual gasses after evacuation, by either chemical recombination or by adsorption, but sometimes gas is released back, or exuded by the materials from which the tube is made.
Gas is tested as the last test, when the tube has warmed up sufficiently.
1. Follow Ron's advice and replace the caps first. It is simple, especially if you do not restuff the old ones and simply replace them (although with Philcos I'd restuff them to keep the appearance: it is also fairly simple with those black backelites).
2. To test a tube for gas you need a tester that tests for gas; I take it not every tube tester does it, but most Hickoks do. If you have a tester, see if it tests for gas; usually the word "gas" appears on the front panel over some buttons and in the manual.
What gas does is cause unplanned ionization (there should be no ions in a tube) radically changing tube's VA characteristics. Getter is pllaced inside tubes to bind residual gasses after evacuation, by either chemical recombination or by adsorption, but sometimes gas is released back, or exuded by the materials from which the tube is made.
Gas is tested as the last test, when the tube has warmed up sufficiently.
