If you know the pinouts, you can apply filament voltage ACor DC, and connect the cathode to DC common. Connect a variable DC voltage between the control grid and the cathode with negative side at the cathode. Connect a high voltage (about 100 volts positive) at the anode (Plate) with a milliamp meter in the plate circuit, and connect the negative end to the cathode. If there is a screen grid connect it to the plate through a resistor. Gradually ramp up the grid voltage and compare it to the plate current. If you plot this it will represent the gain (Mu) of the tube. If the plate current does not change with grid voltage the tube is defunct. If the plate current is always pegged, the tube is defunct. If this EG-IP curve is reasonable, the tube is good. If you can get a tube manual it will help with the settings. I don't know if a manual is available on line. There are many different kinds of tubes. Mixers require more connections to test. Also, if you have a function generator you could capacitively couple a signal to the control grid with a large resistor tied from the CG to the cathode. The cathode is sometimes the common connection and sometimes it has a positive voltage if it is tied to ground through a resistor. This test is more definitive if you have the manufacturer's information, or a tube manual. BTW, What is the tube number? ----- Original Message ----- From: "Dave King" To: "pic microcontroller discussion list" Sent: Saturday, November 11, 2006 6:08 PM Subject: [EE]: Tube testing > Can anyone fire up a way back machine and throw me a bone on how to > test tubes with a multi meter? > I know it can be done (to a point) but can't find any specifics on > what to look for. I have a pile of mil-spec > tubes I need to go through and find out if any are good. The primary > ones are some triodes and a few power > beam pentodes. Other than being able to tell if filaments are not > shorted will a meter be able to tell me any more? > > Dave > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.409 / Virus Database: 268.14.1/527 - Release Date: 11/9/2006 > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist