• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Heater winding load question.

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G

Member
Joined 2002
Hi all,

I'm about to heat up the soldering iron and start the final circuit construction of my new SE EL34 amp but I have a question about the heater winding load for you accomplished designers and builders. The current capacity of the heater winding on my power transformer is 8 amps. The load I will be putting on it is only 4 amps total. Is this load big enough that I won't have a high heater voltage (higher than 6.3v) or should I incorporate a couple of power resistors in there as sort of a preemptive precaution?
 
Ex-Moderator
Joined 2003
Your heater voltage will be a gnat's high, but you will be surprised at the voltage drop along your heater wiring. There's only one way to find out. Do it and measure. I doubt if it will be much out.

Your options if there is a significant error are somewhat limited. Mains voltage varies, so you would need to know the voltage going into the transformer precisely before fiddling.

Suck it and see.
 
I'd guess at about 5% higher than full load.
this is well within experimental tolerances.
As EC8010 recommends, don't worry about it at this stage. It could be that the heaters end up exactly right because of other factors. Alternatively they might just end up 10% high, in which case do something - but later.
 
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