An 866A has a 2.5 volt filament which draws 5 amps.. It's the 5 amps which is a problem. Due to internal drop of the wiring in your tester it needs to be set to 4.3 in order to have 2.5 volts at filament pins.
866 Jr is a little better. It has a 2.5 volt filament @ 2.5 amps. 866 Jr uses 4B basing, same as an 81 tube but can supply more current. Set it up as an 81 wwith 2.5 or 3 volt filament. Change loading to what an 866A uses on your tester. Don't know your specific tester settings but you will know if it's good by a blue glow and meter reading.
Norm
:Greetings- Just picked up a pair of Taylor 866Jr rectifiers and thought that I could test them on my Hickock 533A because the chart lists the 866A. However, on closer examination, the chart says 4.3 volts for the filament which I thought was 2.5 volts @ 5 amps. In any case, can this 866jr be tested on my Hickock, and if so, what are the correct settings? ( the 866jr doesn't have a top cap like the 866A). Thanks very much. Paul
Norm- Thanks once again for your invaluable information.I set up the tester just as you had suggested and sure enough we've got a beautiful blue glow along with a great test result. Also glad to learn thar JR only draws 2.5 amps, as NJ7P web site lists it as drawing 5 amperes. Paul