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tubelab se R3

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Nikon1975

Member
Joined 2009
Question: I have 5.1 V on the filaments of the drivers of my tubelab SE. Filaments of the 300B is correct 4.9something V.

Shouldn't be 6.3 ? I lose 1 V across R3, and this is also correct 2.2 ohm, 0.6 A, makes 1V drop. What's the role of R3 ? What if I shorten it ? What if I put a 6.3 V regulator instead ?

Thanks,

Davide
 
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nightanole

Member
Joined 2009
No your on the money at 5v. The SE can be setup for 2.5v or 5v heater.

Ok go with me on this:

Yes most heaters and the transformer are 6.3 vac
They key is vac
once rectified it turns to 8.88vdc less diode drop
The limit of a 300b is like 5.3v and you can run them at lower 4.3v with longer life but reduced output, 5vcd is the sweet spot

http://www.emissionlabs.com/datasheets/EML300B.htm

So depending on your build you want to see 5vcd or 2.5vcd based on what jumpers you installed.
 
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Nikon1975

Member
Joined 2009
Is it a general rule ? From the data-sheet of the 5842 I understand that the heater should be fed with 6.3 VAC or 6.3VDC. At the moment I am feeding them with 5.2VDC +0.3V ripple.
The jumpers set the voltage of the power tubes, the drivers should stay at 6.3V.

Thanks,

Davide
 
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