I am trying to figure out how much current I have available from a power tranformer I have and how much I need for an amp. Here is where I am confused:
A Hammond 272FX is rated at 300-0-300@150mA but it is a 146VA device. It has a 5v@3A (15VA) winding and a 6.3v@5A (31.5VA) winding. When added together they total 46.5VA leaving 99.5VA remaining for the B+. 99.5VA/300V = 331mA. Is this how much current I have available or do I have half this amount as the rectifiers draw current from each half of the winding? How does this relate to the 150mA rating? In a D'Lite, for example, how much current do I need? The D'Lite uses Vibrolux iron which has ratings of 325-0-325@180mA and if I can't go by the 180mA rating how do I figure out how much current is available?
Sorry for the myriad of questions but they all sort of interelate. Any help from the advanced builders here would be greatly appreciated. I am really happy that there is a place like this out here to ask questions like these. Keep up the good work.
-Kevin
Transformer Current Question
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David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: Transformer Current Question
It's 166 mA if you're using it with a full wave half bridge rectifier, which is the normal kind. I.E. a tube rectifier or a pair or pairs of diodes in parallel. So Hammond rating it at 150 mA is slightly conservative on the numbers.
So it's probably OK for the D'Lite, current wise, based on the numbers. Hammond is pretty conservative on their ratings. However, it's a bit light on DC voltage, by (325-300)*1.3 to 1.4 (tube or SS rectifier). I would recomend you take a look at Dave Allen's Vibrolux power transformer, www.allenamps.com, 180 mA, 320-0-320 VAC, I have used it, it is excellent in the Vibrolux circuit, and reasonably priced too.
There is a constant argument in the MI amp community for and against Hammond output transformers for use in guitar amps, but I'm not aware of any regarding their power transformers.
So it's probably OK for the D'Lite, current wise, based on the numbers. Hammond is pretty conservative on their ratings. However, it's a bit light on DC voltage, by (325-300)*1.3 to 1.4 (tube or SS rectifier). I would recomend you take a look at Dave Allen's Vibrolux power transformer, www.allenamps.com, 180 mA, 320-0-320 VAC, I have used it, it is excellent in the Vibrolux circuit, and reasonably priced too.
There is a constant argument in the MI amp community for and against Hammond output transformers for use in guitar amps, but I'm not aware of any regarding their power transformers.
Re: Transformer Current Question
Excellent. That is the information I was looking for. I will definitely check out Allen's transformer. Thank you so much David.
-Kevin
-Kevin
Re: Transformer Current Question
FWIW, here's the most current spec's on the D'Lite xfmrs:
Transformer set for the D'LITE22.
Power Transformers Specs: 120v Primary
325 V secondary taps @225 mA, center tapped (325v-0-325v)
6.3V CT @ 4.3A (3.15v-0-3.15v)
5V & 6.3V @ 3 A (5v-6.3v-0) You can use most rectifiers with this setup, 5Y3, 6CA4, GZ34, 6AX5GT, 5U4GB, etc.
Output Transformers Specs: 8K Primary with selectable 4-8-16 Ohm secondary taps.
Transformer set for the D'LITE22.
Power Transformers Specs: 120v Primary
325 V secondary taps @225 mA, center tapped (325v-0-325v)
6.3V CT @ 4.3A (3.15v-0-3.15v)
5V & 6.3V @ 3 A (5v-6.3v-0) You can use most rectifiers with this setup, 5Y3, 6CA4, GZ34, 6AX5GT, 5U4GB, etc.
Output Transformers Specs: 8K Primary with selectable 4-8-16 Ohm secondary taps.