Salas hotrodded blue DCB1 build - Page 9 - diyAudio
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Old 20th August 2010, 08:14 PM   #81
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Looking for a TX for a hotrod build, would this be ok

Amveco Magnetics 70063K
dual 115Vac inputs and dual 15Vac output at 12.5Va

Also found this but might be too much,

Chia Yu Co Ltd * Input: 2 X 120Vac 50-60Hz 3" Dia X 1 1/2" Tall Output 42Vct 21V- 0 - 21V 80VA
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Old 20th August 2010, 08:19 PM   #82
Salas is offline Salas  Greece
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Get a dual 15V 50VA IMHO. Although you can calculate 12VA for 2x0.2A draw, let it breathe well. At least a 30VA.
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Old 20th August 2010, 08:20 PM   #83
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Amveco too low. Otherwone too high AC.
Look for an Antek transformer since your in the states. Would get a 50-100va 12 or 15v.
Cheap, works, good quality.
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Old 20th August 2010, 10:12 PM   #84
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would putting 15v regulators at the output of the 42Vct 21V- 0 - 21V 80VA TX be out of the question. I ask only because it would be way cheaper than getting a new TX.

Any negative aspects to what I am suggesting?

Thanks for everyones input
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Old 20th August 2010, 10:27 PM   #85
Salas is offline Salas  Greece
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That is effectively pre regulating. Technically sound, but a large drop times high constant current will produce heat also on the pre reg, plus you introduce complexity that will give a different subjective result since you are wrapping the super reg in a typical chip. I would much more prefer a CRC passive pre filter, with resistors of value and Wattage/sinking to drop properly. That rectified and filtered output has to go directly to the filter caps pads on the blue at +/-20V DCin. Maybe 39R 5W amongst two 4700uF made externally or by hacking the board. That would drop about 8V for each rail of a +/-200mA set CCS on a blue.
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Old 20th August 2010, 10:49 PM   #86
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Thank you sir, understood. So TX is ok as long as using passive pre filter but that would be complicated for my expertise wouldn't know where to start with pre filter. I will keep looking for 15v TX.
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Old 20th August 2010, 11:05 PM   #87
Salas is offline Salas  Greece
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You can break the copper connections between + to + and - to - of blue's 4700uF pos and neg filter cap pairs and introduce a 39R 5W per rail between them underneath. With 8R2 5W set resistors where it says 10R 5W, will surely create an around +/-20VDC final DCin to the regs when using a 2x21VAC trafo. Use 35V caps, no less.
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Old 20th August 2010, 11:17 PM   #88
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Salas, Vdrop on my notorious leds is between 1.683v & 1.712v, so I can't get 5.4 or 9v strings with these leds. Does it matter?

They average out at 1.7v DC with a 9v battery and a 1K0 resistor. Can I aim for 5.1v & 8.5v if they're matched per regulator side?

Many thanks as ever
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Old 20th August 2010, 11:19 PM   #89
Salas is offline Salas  Greece
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It will give less than +/-10Vout and it will need smaller value set resistors for same CCS setting target, that is all. Making a full DCB1 too?
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Old 20th August 2010, 11:25 PM   #90
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Yeah, I bought 3x blue boards & a mesmerize too. Why so many I can't say. I missed the GB for the Mes and so when blue came around I got a bit carried away.

I've hacked one blue board to bits as you know.

Great project Salas, not least because you're here to hold our hand. How in hell do you speak such good English?
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