Quote:
Originally Posted by jr_tech
My childhood Arvin 446p used 2 zinc carbon cells in parallel to power filaments of a similar tube complement (3S4, 1U5, 1T4, 1R5) which seemed to work fine. Of course today I use Alkaline cells!
jr
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The battery only portables seemed to have the filaments in parallel.
The so-called 3 way portables, AC/DC battery sets had the tube filaments in series in order to run them off the B+ supply using a large voltage dropping resistor, when operating off the power line.
The simpler designs used a 7.5 or 9 volt battery for the "A" supply, depending on the tube count. The more complicated designs used either 1.5 or 3 volt "A" supply. The power change over switching was more involved because the tube filaments had to be switched to series-parallel or parallel, plus having to take the cathode biasing into consideration.
01-23-2017, 07:59 PM
Hybrid Mode
