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Question about current ratings of Hammond 300 series power transformers.

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G

G

Member
Joined 2002
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!
 
Rod Coleman

Rod Coleman

Member
Joined 2004
If you had a circuit that required 85mA would you hesitate to use a Hammond power transformer rated for 100mA?
Click to expand...

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

Tubelab_com

Member
Joined 2005
tubelab.com
But if the 85mA is the current taken from the dc (rectified) supply then you'll need more like a 200mA rating.
Click to expand...

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

G

Member
Joined 2002
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.
 
G

G

Member
Joined 2002
Ty_Bower said:
Have you tried looking through the .pdf of all Edcor's power transformers? They might have something in there...

http://www.audiotransformers.net/forum/index.php?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.
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Spot On! I just ordered the 105 and the 104. They are running about 3 weeks behind though but that is just fine. They look like really nice transformers and their specs are perfect for my new preamp/amp! I had forgotten about Edcor. Thank you. Bandersnatch is going to drool all over himself when I post pics of the 12B4a powerhouse amp I'm building.;)
 
Geek

Geek

Member
Joined 2004
Evenharmonics said:
I would try others like Edcor.
Hammond's PT spec and actual numbers are not very close.
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I found the current ratings OK, but voltages to be somewhat highish.

Example, I have a 279GX here rated 225-0-225 @ 65mA and 6.3V @ 2.5A. At full load she delivers 250-0-250 HV and 6.7V heater :eek:


G said:
They are running about 3 weeks behind though but that is just fine.
Click to expand...

Good to hear their business is picking up. They were 2 weeks behind last week :)

Cheers!
 
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