Question about current ratings of Hammond 300 series power transformers.

[G]

Hi all. If you had a circuit that required 85mA would you hesitate to use a Hammond power transformer rated for 100mA? Also, if the filaments of said circuit required 1.8A would you use the 2A winding on the same transformer? I don't want any problems in the future!

[Geek]

I would call that the "perfect match" transformer myself

Cheers!

[G]

Originally posted by Geek
I would call that the "perfect match" transformer myself

Cheers!

Cool! Last question. Is a 125-0-125v transformer considered a 250v center tapped transformer?

[Geek]

Yes, it is!

Sounds like you're building a little SE power amp or a preamp with 6-8 tubes?

Cheers!

[G]

Originally posted by Geek
Yes, it is!

Sounds like you're building a little SE power amp or a preamp with 6-8 tubes?

Cheers!

SE 12B4A amplifier. A 1.25 watt monster!

[Rod Coleman]

If you had a circuit that required 85mA would you hesitate to use a Hammond power transformer rated for 100mA?

If you mean 85mA ac measured from the transformer then that would be OK.

But if the 85mA is the current taken from the dc (rectified) supply then you'll need more like a 200mA rating. The value of the transformer current depends on the value of capacitance after the rectifier, and the whether it's choke or cap input architecture.

work out the current by using PSUD2:

http://www.duncanamps.com/psud2/index.html

this works near perfectly on Linux platforms (using the WINE environment) so you can dump that Conficker-riddled Windows and use DIY friendly OS

http://www.kubuntu.org/

[tubelab.com]

But if the 85mA is the current taken from the dc (rectified) supply then you'll need more like a 200mA rating.

Hammond transformers are specified for DC current draw. From their web site:

"High voltage current is D.C. using C.T. Full Wave rectifier - capacitor input".

I am guessing that we are talking about a 369AXP which will make about 150 to 160 volts DC (just my guess) using solid state diodes and a capacitor input filter. There would be no problem drawing 100 mA from this supply. Even more could be drawn if you are running it on 60Hz since the 300 series is rated for 50Hz.

[G]

Well I wanted to use this PSU:

http://www.welbornelabs.com/ps10.htm

but I can't find the right transformer for the job. I need a 360v-400v center tapped transformer that will supply at least 150mA. Any suggestions? Hammond does not make such a animal.

[G]

I suppose I could stick with a 5AR4 rectifier and use a Hammond 370FX. I'm assuming that the 5AR4 will drop some of the excess voltage. I would like for the regulator to run cool without having to drop too many watts to get to the target voltage of 215v.

[Ty_Bower]

Have you tried looking through the .pdf of all Edcor's power transformers? They might have something in there...

http://www.audiotransformers.net/for...hp?topic=198.0

The first one I see might be an XPWR105. It says it is good for 360 VCT at 250 mA, and 6.3V at 3 amps. There might be other candidates in the list too.