Let's forget the first circuit.
I am sure that the second appears to work -for now- (and maybe forever), but leaving the cathode of the LEDs ~floating when the other side is connected to the mains is not a good idea, especially for the white one, which remains connected to the (inactive) PSU. They can catch all sorts of stray voltages, which come from a very high impedance and are benign with regular LEDs, but modern blue and parented Leds do not like this kind of treatment and might fail unexpectedly.
An antiparalell 1N4148 on each Led costs nears to nothing, but buys you peace of mind, which invaluable
It seemed there are brutal full frontal nudity electronics in promiscuous poses on these pages.
We are friends for life. You forgot the word "blue" though.
@Elvee: you sold the antiparallel diode to me. Will do so next time but it may take a while as they seem to be made for DC.
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I use an IN-12B for which input... 0 for phono, etc.
Red power button for standby, green for 12V supply, blue for 320V supply... -110V is indicated by the presence of 320V and a glow from a 0A3.. Failsafe - The bias supply powers a relay for power to the plate circuit (110V) - no blue LED. If 12V fails, no green or any other LEDs... If 320V fails, you get the glow tube lit up but no blue LED. If everything light up and no sound look for a failure in the 640V quadrupler supply... The entire thing runs from a 120V isolation transformer.
And the whole thing is DC. Only my oldest design uses an AC voltage for an LED. Not because it'll burn out, just because I hate the flicker 🙂
Red power button for standby, green for 12V supply, blue for 320V supply... -110V is indicated by the presence of 320V and a glow from a 0A3.. Failsafe - The bias supply powers a relay for power to the plate circuit (110V) - no blue LED. If 12V fails, no green or any other LEDs... If 320V fails, you get the glow tube lit up but no blue LED. If everything light up and no sound look for a failure in the 640V quadrupler supply... The entire thing runs from a 120V isolation transformer.
And the whole thing is DC. Only my oldest design uses an AC voltage for an LED. Not because it'll burn out, just because I hate the flicker 🙂
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I take that risk (imo theoretically and small) and see what happens over time in daily use.
I had specified a specific small PCB area for this circuit and initially an anti-parallel diode on each LED. But that collided with my self-imposed requirement that all conductor tracks that carry mains voltage should be at least 4mm apart. There just wasn't enough space and that's how the single diode came about.
😉 I have to set priorities. My peace of mind depends more on my 4mm rule than an eventually blown LED.🙂
Ok you bring higher voltage, even mains voltage to a sensitive blue LED with long cabling and then insist on 4 mm distance. Understood 😉 I have gutted a telecom device that used plastic light tubes to the LEDs over the distance to the front panel, seemed a nice and safe but expensive way of doing things. The LEDs were SMD and included on the mains voltage/PSU board.
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Just teasing. One sees strange things these days anyway so not many surprises anymore. Granddad's designs on the contrary can be so ingenious that one overlooks clever design choices and overall criteria with todays mindset. Modern throw away low cost optimized electronics sometimes have oddities and plain design errors directly conflicting with their low cost main parameter. The 25 Euro Merus amplifiers with both an expensive film input cap in series with an SMD ceramic input cap for instance.
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...... a final update perhaps ....... with the anti-parallel diode, the blue LED is still working, estimated use about 30-50 hours.
If I move may head around or move the power supply it is fitted in, I can see it 'pulse' but not when looking at it normally, so flashing is not an issue.
If I move may head around or move the power supply it is fitted in, I can see it 'pulse' but not when looking at it normally, so flashing is not an issue.