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Old 16th October 2012, 03:30 AM   #91
Pano is offline Pano  United States
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No cap needed on the LED. I did leave out the bias cap on the Pentode.
In my app I'm pulling about 6mA thru a red LED (1.75V)
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Old 16th October 2012, 03:31 AM   #92
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Quote:
Originally Posted by Bigun View Post
Is one of the parts you left out a capacitor ? just wondering if without a bypass capacitor you are now going to have a.c. across the diode. And we know what that means...
Yes, you do get AC thru a forward biased diode..
No bypass cap required...

-very respectfully;
-gary
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Old 16th October 2012, 03:40 AM   #93
Pano is offline Pano  United States
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I thought (for 3 seconds) "Do I want a bypass cap on the resistor below the LED?"

Duh, no! Who knows why?
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Old 16th October 2012, 03:58 AM   #94
dgta is offline dgta  United States
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Never mind...

Last edited by dgta; 16th October 2012 at 04:02 AM.
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Old 3rd November 2012, 07:18 PM   #95
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Has anyone ever set up a concertina / split load phase inverter with LED bias?

With a 300v B+ I'm planning to use a 6CG7 with 22k at anode. Grid has 470k coming off it that joins the bottom of a string of 3 red LED's under the cathode, followed by the second 22k to ground. The 2 signal feeds to the output tubes comes from anode and from below the 3 LED's respectively.

Any of the LED users see a reason as to why this won't work?
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Old 3rd November 2012, 07:23 PM   #96
tvrgeek is offline tvrgeek  United States
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One of these days I need to quit building speakers and finish my RLD. It is a modified Meng P61, which is no longer a P61 anyway. I keep meaning to build some really efficient speakers but my brief adventures with full range drivers sent me back to traditional inefficient multi-way speakers totally unsuitable for a 7 W amp.
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Old 3rd November 2012, 07:41 PM   #97
Doug R is offline Doug R  United States
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Hi Guys,
I have what is very likely a dumb/newb question, can you parallel a resistor + LED(s) instead of a resistor + cap in the cathode (since AC can pass through the LED)?
Doug
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Old 3rd November 2012, 08:47 PM   #98
DF96 is offline DF96  England
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With an LED, what is the parallel resistor for?
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Old 3rd November 2012, 09:15 PM   #99
Doug R is offline Doug R  United States
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Well, as I said, it's a naive question, but I have just been wondering if one could reasonably use LEDs when the cathode sits at a pretty high voltage, i.e. 70v for a 300b.
Doug
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Old 3rd November 2012, 09:31 PM   #100
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally Posted by Doug R View Post
I have just been wondering if one could reasonably use LEDs when the cathode sits at a pretty high voltage
Yes, no problem with that.
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