After watching a youtube video I learned something quite new to me.
Most radio and TV forum members will be familiar with the idea of running valve heaters in series in particular the TV people (“U” series at 100mA and “P” series at 300mA) . The dial lamp can also be designed into the series circuit , being of the same current value as the valve heaters.
The video talks of tap in the 35Z5 rectifier diode. This is not a centre tap as you would think (for example used in 3S4 , 3V4 , 12AH8 , 12AU7 , 12AX7 to name a few ) but is a special one that you can add a suitable lamp (or resistor) in PARALLEL with it and not burn out the “other half” (or
valves in the rest of the string)... all new to me! (also,you?)
I will raise the following questions…
1) Has it been used in the UK or an American thing (“all American five”)
2) Has it been used in any other applications other than in TV /radio
3) Any other valves with an “off” centre tap ( found 35W4 also)
4) Is it just limited to diode/ rectifiers
link to video
https://www.youtube.com/watch?v=Xbgs_BhNxXY
(jump in at 7-40)
link to valve data
35Z5
http://www.r-type.org/exhib/aaa0889.htm
35W4
http://www.r-type.org/exhib/aaa0908.htm
Other info here
http://www.philcorepairbench.com/tips/svctip40.htm
regards S-W