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It is currently 05 Dec 2016, 13:42

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PostPosted: 17 Oct 2016, 14:23 
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IMG_5214_opt.jpg

I just uploaded a schematic of a circuit, and I need some help with it. The LED is a two color indicator, that is powered from the 6.3VAC filament supply for a 12AX7 tube. The LED indicates the condition of a "fat" switch that feeds the plates, and it is controlled by a switch operated SPDT relay. The schematic only shows the indicator circuit. This all worked before I had to change the ground reference. The two 100 ohm resistors used to connect directly to ground. How do I get the indicator working with this new arrangement?


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PostPosted: 17 Oct 2016, 15:45 
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Is it only the indicator that is not working? And does it matter that it is/is not tied into the circuit? In other words, could you use a DPDT relay to switch the indicator and the plate switch? Would that not have the same net function with less complexity?


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PostPosted: 17 Oct 2016, 15:56 
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I'm sorry. It is a DPDT relay that is being used. Everything else works perfectly. It doesn't work unless I connect the two 100 ohm resistors to ground, no matter what I've tried so far.


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PostPosted: 17 Oct 2016, 16:25 
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Probably need to reference the transistor emitters to the voltage divider where the 100 ohm resistors are now referenced.


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PostPosted: 17 Oct 2016, 18:53 
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famousmockingbird wrote:
Probably need to reference the transistor emitters to the voltage divider where the 100 ohm resistors are now referenced.

That makes hum, but the light works.


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PostPosted: 17 Oct 2016, 22:24 
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Okay I have another option.

Reference the transistor emitters to the negative side of the switch (anode side of diodes at bridge).


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PostPosted: 18 Oct 2016, 13:14 
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Too much hum there, too. No hum when light not working.


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PostPosted: 18 Oct 2016, 14:26 
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Item Number: 504M02QA100
Brand: Cornell-Dubilier

Maybe something like this to clamp the hum? Just a random thought - There may be a hundred reasons why not, but I have used small chokes in the past to remove spurious signals.


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PostPosted: 18 Oct 2016, 15:55 
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Peter W. wrote:
Item Number: 504M02QA100
Brand: Cornell-Dubilier

Maybe something like this to clamp the hum? Just a random thought - There may be a hundred reasons why not, but I have used small chokes in the past to remove spurious signals.

A .5uf metalized film polyester capacitor? Where would I put it in the circuit?


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PostPosted: 18 Oct 2016, 17:16 
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Can I ask what may be a silly question? Why don't you just run an LED directly off of the B+ line after the switch? I do it all the time on amps with SS rectifiers and B+ switches.

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