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Vintage threads from the first ten years
Filament transformer assistance
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 9/1/2000 3:24 PM |
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Dave |
Filament transformer assistance I'd like to use 6550's in my homebrew amp. It has a Super Reverb power tranny which probably won't be able to put out the current needed. The idea is to add a dedicated transformer like the 12.6v w/center tap from Radio Shack to run the power tubes,as I need 3.2 amps for the 6550 filaments. Could someone please guide me in how to wire up the secondary? |
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| 9/1/2000 3:31 PM |
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| Gil Ayan |
Hi David, I don't know whether RS will have a 12.6VAC transformer that can handle all of your 3.2A requirement. But let's assume you can find one such transformer. Since it is 12.6VAC with a center tap, you can wire the output in parallel, thus getting 6.3VAC at roughly twice the amperage the thing is rated for at 12.6VAC. So, tie the two ends together (these are the yellow wires in the RS 126.V transformers) and use that and the black wire (center tap) as your filament source. You will need to reference the voltage to ground via a pair of 100 ohm resistors, since you will no longer have a center tap per se. Gil | |
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| 9/1/2000 3:37 PM |
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| Dave |
Thanks much!! |
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| 9/2/2000 7:22 AM |
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| Steve A. |
Dave: Another game plan would be to use your existing PT filament windings to power the 6550's and then add a small 6.3 or 12.6vac tranny to run just the 12A_7 filaments (possibly with DC for less hum). While you are at it you might try "biasing up" the AC heater voltage for the 6550's with ~50vdc... that is supposed to reduce some of the miscellaneous noises you might hear (the "sh-h-h-h" from the power tubes, maybe?) Good to hear from you again! Steve Ahola |
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