Old transformer. Is it usable?

tomastb · 17th July 2009, 10:14 PM

Hello

I'm planning on making my first chip amp using an LM4780 and I just got a JVC R-S5 receiver to use for the case. This old receiver has a 22.5V-0-22.5V secondary at 2A transformer (serial number e03077-40D).

I'm pretty sure that this transformer cannot supply enough current but just wanted to double check here. I'm on a tight budget and using this transformer would save me a lot of money by not having to buy a new one.

Thanks

star882 · 17th July 2009, 10:58 PM

It will probably be enough. Remember, real world audio is not a constant load nor does it load the supply to maximum very often with reasonable use. The transformer will survive a brief overload. The real test is to just build it and use it. If the transformer is staying cool, it's enough.

paulb · 17th July 2009, 11:02 PM

Absolutely. Use it.

tomastb · 18th July 2009, 07:43 PM

Ok thanks for the help. saves me some cash

AndrewT · 20th July 2009, 04:30 PM

yes,
22.5+22.5Vac @ 2Aac = 90VA.
That is good enough for 45W to 90W of total output power.

Do check the maximum open circuit secondary voltage, when mains is at maximum. Then select the smoothing cap working voltage to exceed the worst case peak voltage that the transformer can supply.

guitaristz · 22nd July 2009, 11:28 AM

Way to recycle Tomastb. Is that a toroid type or not and how's it working for you?
And guys, thanks for the basic math that helps a lot.

tomastb · 24th July 2009, 07:46 AM

It's not a toroid. I haven't tried it out yet. I've just finished getting my parts list for the amp. Now I just have to get motivated around exams and build it.

17th July 2009, 10:14 PM	#1
tomastb diyAudio Member Join Date: Mar 2009	Old transformer. Is it usable? Hello I'm planning on making my first chip amp using an LM4780 and I just got a JVC R-S5 receiver to use for the case. This old receiver has a 22.5V-0-22.5V secondary at 2A transformer (serial number e03077-40D). I'm pretty sure that this transformer cannot supply enough current but just wanted to double check here. I'm on a tight budget and using this transformer would save me a lot of money by not having to buy a new one. Thanks

17th July 2009, 10:58 PM	#2
star882 diyAudio Member Join Date: Mar 2007	It will probably be enough. Remember, real world audio is not a constant load nor does it load the supply to maximum very often with reasonable use. The transformer will survive a brief overload. The real test is to just build it and use it. If the transformer is staying cool, it's enough. __________________ "Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!

20th July 2009, 04:30 PM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	yes, 22.5+22.5Vac @ 2Aac = 90VA. That is good enough for 45W to 90W of total output power. Do check the maximum open circuit secondary voltage, when mains is at maximum. Then select the smoothing cap working voltage to exceed the worst case peak voltage that the transformer can supply. __________________ regards Andrew T.

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17th July 2009, 11:02 PM	#3
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	Absolutely. Use it.

18th July 2009, 07:43 PM	#4
tomastb diyAudio Member Join Date: Mar 2009	Ok thanks for the help. saves me some cash

22nd July 2009, 11:28 AM	#6
guitaristz diyAudio Member Join Date: Oct 2006	Way to recycle Tomastb. Is that a toroid type or not and how's it working for you? And guys, thanks for the basic math that helps a lot.

24th July 2009, 07:46 AM	#7
tomastb diyAudio Member Join Date: Mar 2009	It's not a toroid. I haven't tried it out yet. I've just finished getting my parts list for the amp. Now I just have to get motivated around exams and build it.

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