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PostPosted: 22 Dec 2008, 12:41 
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I have a big question about the 5U4 tube. First of all can they be paralleled to provide more current capability, and second, can there filaments be wired in series so I can use the 10V transformer that I have?

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PostPosted: 22 Dec 2008, 14:53 
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Location: Dayton, Ohio
Yes, you can. I've seen it done many times.

You can wire the filaments in series, however, take the output power to your circuit in the center where the two filaments come together. This will equalize the current flow between the two tubes.

Good luck on your project!

-Steve

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PostPosted: 22 Dec 2008, 16:28 
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Thanks for the info. this won't be the last question I will have actually I do have another, I was originally going to have DC filament supplies for the output tubes of the amplifier, the tubes are 6L6GC's which only draw an amp of current at 6.3V but KT77's draw 1.5 amps and for a pair that will total 3A! and that is what the LT1085 regulator is rated at, will it still work if I put it on a massive heat sink to keep it cool or will I have to go for the 5A version?

I suppose the other option would be to just run the filaments on the 6.3Vac of the 8A transformer that I have.

Thanks for your time :up:

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PostPosted: 22 Dec 2008, 18:38 
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I got some schematics drawn up, too bad the resolution is all messed up but oh well. The power tranny I am using is the beasty Hammond 400-0-400V at 465mA, and I am using a 500mA 10H choke with it.


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PostPosted: 06 Sep 2009, 20:18 
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This is based around the same topic of the use of a rectifier tube in a power supply, so I decided it not worth making a new thread, instead add on to one, and thus I need to change the name of the thread as well.

Ok, the problem I am having is getting the 5VAC for the rectifier on my PF C8 preamp, the setup I have is not getting me the voltages needed for both 12V and 6.3V filaments, the only other solution is to use a 12V tranny and a 5V tranny..... But I do not have a 5V 3A tranny on hand, but the Hammond 269JX has a 6.3V 2.5A winding, is there an easy way to get this down to 5V? Is it possible to go DC? What are my options other than using a 6X4 that may have a bit of struggle with the supply I have.

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PostPosted: 06 Sep 2009, 20:44 
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You could go from 6.3 to 5V with a resistor, but the 6.3V 2.5A transformer may not do so well with a 3A load.
Cheers

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PostPosted: 07 Sep 2009, 10:12 
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I did forget to mention that I am using a 5Y3 which only draws 2A at 5V so 2.5A would be ok but from what I calculated I would need a 3 ohm resistor rated for like 15 watts 25 watts to keep things cool, am I right Gio?

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PostPosted: 08 Sep 2009, 12:42 
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Try a 0.68R 5W or 1R 5W+ and see how close that gets you. With 1R, 5W will get pretty hot. Above 1R you will need to move towards 7W or 10W.

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PostPosted: 08 Sep 2009, 19:31 
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What ever you say, I will try it I have a 1 ohm 10W and I have a 1.5 ohm 20 watt, 2.2 ohm 15 watt.... and what looks like to be a supermite 220 ohm 100 watt or bigger resistor, I think you might want to see this beast! Have no idea what it would be for at a rating of 220 ohms. :)

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PostPosted: 09 Sep 2009, 14:50 
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1.5 seems to get me 4.35 or so and it gets damn hot in my opinion, but I guess it will survive anyway at 80-85 digrees C?

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