• 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 supply (xformer specs are 6.3V 2.5A) as supply for a power LED?

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Agreed, the LED will self-rectify, and the 1k resistor limits reverse current, but it's a bit naughty. Also half-wave rectification means that you pass DC through your transformer, which is also undesirable. 1N4148 is so cheap (a penny) when you buy 100 that you might as well use it...
 
Sch3mat1c said:
Any transformer will tolerate DC. Period. How much depends on construction.*
...
Tim

* italics mine

I agree. Put an air gap in the main flux path and you can put all the dc through the transformer the wire will allow. But I didn't say a regular old transformer couldn't tolerate DC, Tim, I said such would affect the AC performance parameters.

No matter how you slice it, saving a penny by omitting the reverse biased diode across the LED is poor engineering. It may not degrade performance much practically speaking, but why let it occur in the first place if the solution is so simple?
 
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