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surfstu 26th January 2013 12:35 AM

PSU id and help (psu designer ii)
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I have a transformer from an old heathkit s99, I presume it is approx 200ma but I'm not sure. I've attached a schematic for the circuit it came from. It was powering 4ecl86 and 3 ecc83's and 2 ef86's.

I have no idea of what values to enter into duncans psu designer, is the RMS V = 270 x 1.414 = 381V - and then how do I calculate the source resistance?

Is there a way to calculate more info from this transformer seeing as on the full scematic

HT 1 = 320V
HT 2 = 270V
HT 3 = 250V

cheers Stuart

DUG 26th January 2013 04:17 AM

"I have no idea of what values to enter into duncans psu designer, is the RMS V = 270 x 1.414 = 381V - and then how do I calculate the source resistance?"

look at the data sheet for V10: GZ34

Hope that helps.

DF96 26th January 2013 01:48 PM

RMS voltage is 270V. Peak will be 381V. I believe PSUD2 uses RMS, so enter 270V. For source resistance measure primary and secondary resistance with a DVM, and then enter the results into the PSUD2 transformer calculator (or do the calculation yourself).

surfstu 26th January 2013 02:18 PM

Thanks Df96, I didn't realise I could just stick a DVM on primary winding (mains side?) and then over the secondary winding (leave CT out?) to get resistances - that I could then apply to a formula to find the source resistance!

If I then setup a circuit in PSUD2, using full wave rectifier (GZ34) followed by CRCRC will I be able to identify the current throught the circuit by seeing what flows through the final 5K resistor that PSUD2 puts in by default?

Or do I change that final 'resistor to ground' to a resistance that matchs the perceived resistance of the amp I wish to build?

If I wish to build the original Baby Huey amp that gingertubes modded for UL operation, should I be changing the value of the final 5k resistor of PSUD2?

Thanks again for everyones help here, and thanks Dug for the data sheet

DF96 26th January 2013 02:35 PM

I'm not sure about the CT, as I can't remember what PSUD2 assumes for secondary resistance.

You can use either a resistor or constant current load for your PSU. A resistor may better approximate the load of a real valve amplifier. Set it to whatever value is appropriate.

surfstu 26th January 2013 02:40 PM

Thanks DF, but how do I know what value is appropriate for the final R in PSUD2

and... I just read somewhere that the primary resistance is taken across the mains, and the secondary is HALF the secondary... I'm guessing this means CT to one side of the secondary?

surfstu 26th January 2013 02:46 PM

1 Attachment(s)
If this is the circuit I intend to build then is there a way of approximating the final R value?

surfstu 26th January 2013 02:48 PM

1 Attachment(s)
better image!

DF96 26th January 2013 06:38 PM

Find the current, then use Ohm's Law.

surfstu 27th January 2013 04:52 PM

Would it be safe to say that the current drawn by this circuit (4 x ecl86) will be 4 x 35mA which is 140mA?

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