LED problem in Finnish Crack

TT · 3484

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Offline TT

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Reply #15 on: November 25, 2013, 03:16:07 AM
Grainger, thank you for yours suggestions. I will try them tomorrow.
I am novice with tubes. Is the A -tubes heater voltage between A7 and A9?

- Timo -


Offline Grainger49

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Reply #16 on: November 25, 2013, 04:44:28 AM
Should be either A4 or A5 and A9.  A4 and A5 are tied together with that bare wire.


Offline TT

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Reply #17 on: November 26, 2013, 02:58:16 AM
I measured the heater voltage between A4(A5) and A9. It was zero!
Also voltage B7- B8 was zero and on transformer voltage between terminal 4 and terminal 5 was zero.


Offline Grainger49

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Reply #18 on: November 26, 2013, 03:57:48 AM
Ok, I should have said this, it is AC voltage because it comes straight off of the transformer.  It would read zero on the DC scale.  Sorry!  That is important information I left out.

Terminal 4 to terminal 5 should be the DC drop across the plate resistor, 22.1k Ohms.  If the tube is not conducting, it will not drop any voltage.


Offline TT

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Reply #19 on: November 26, 2013, 04:40:32 AM
Oh no! I should understand that! The heater voltage is 5.5 VAC.


Offline Grainger49

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Reply #20 on: November 26, 2013, 05:47:49 AM
That is a bit low but should still get emissions.  That means if the circuit is right the tube should turn on. 

I'm going to have to think about it.


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