Precision Tube Tester 612 and 614 Operating Instructions Sorry, this product cannot be purchased. $7.99 Category: Precision Apparatus Company Related products Precision Tube Tester 620 Operating Manual $8.99 Read more Precision Tube Test Data for 612 614 620 654 Tube Testers $10.99 Read more Precision Model 220 Marker Adder Manual $8.99 Read more Precision Supplementary Tube Test Data for 10-40 Tube Testers $9.99 Read more