Westmore 501 
                                        AKA Triplett 3444
                      Mutual Conductance Laboratory Tube Tester
                                          *Calibrated*
 
See pictures 6 -10 for calibration and other important information.
 
All Electrolytic Capacitors, Diodes, and Bridge Rectifier Replaced 
Tests for Mutual Conductance (Gm), Noise, Shorts, Leakage, Plate Current, Remaining Life
Capable of Testing to Tube Manufacturer's Voltages
Filtered Plate and Screen Voltages to 250 VDC and Bias to -50 VDC
Tests Both sections of Dual Section Tubes Without Resetting Selectors
Measures Plate Current up to 50 Milliamps on Main Meter
Measures Gm up to 30,000 Micromhos
Gm Check Self-Calibration Feature
Illuminated Main Meter and Roll Chart 
 
From Radiomuseum:
Westmore 501 Tube Tester. Made Between 1959 and 1967. This Tester was made by the Triplett Company and sold under the Westmore name. The same model from Triplett is a model 3444. This model has a 5kHz oscillator for a signal supply and can also read plate current up to 50ma. The Triplet 3444 and Westmore 501 were listed as a Labortory Grade tube Tester. This tester can use the tube manufactures data sheet to setup a test for a tube not listed in the roll charts.
The only difference between the 501 and the 3444 is an added lamp in series with the AC line, as an overload indicator. This was also incorporated into the 3444A. The 501 manual is similar to the 3444 manual, but rewritten and rearranged. It reads "anode" instead of "plate". The manual also has a guarantee for government contracts. Alan Douglas is concluding that the 501 was a model made by Triplett to fill a government contract (could have been for the F.A.A.) with a dummy corporation set up for the purpose.
 
A DVD with manual and tube data will be included, or I can email the contents of the DVD.
 
Please see the calibration information in the pictures.
 
Free Insured Shipping in 48 Contiguous USA
 
Please contact in advance of purchase for shipping costs internationally. You can generally determine the shipping costs to your location by using 24X24X12” box weighing 28 pounds shipped from zip code 86332. We ship internationally with FedEx and USPS.