Precision Tube Tester 612 and 614 Operating Instructions Sorry, this product cannot be purchased. $7.99 Category: Precision Apparatus Company Related products 1953 Precision Apparatus E-200 Servicing by Signal Substitution Manual $10.99 Read more Precision Tube Test Data for 612 614 620 654 Tube Testers $10.99 Read more Precision Apparatus EV-10A Vacuum Tube Multi-Meter Manual $8.99 Read more Precision Tube Test Data for 10-60 Tester $9.99 Read more