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Power supply woes?
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marinosr



Joined: Jun 30, 2006
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Location: Gambier, OH
PostPosted: Thu Jul 20, 2006 6:55 pm    Post subject: Power supply woes? Reply with quote  Mark this post and the followings unread
So I was at the greatest place on earth recently (Mendelson's Surplus Outlet (www.meci.com)) and I picked up an Astec AC8151 power supply, which has +/-12V and +5V. I'm trying to put together some of Ray Wilson's modules. I was looking at specs for it today, though, and I think I may have erred in buying it. Look at this sheet...
http://www.kev.pulo.com.au/osborne1/documents/o1astecpsac8151/o1astecpsac8151-pg04-lo.jpg

Can I run a synth off of that? Will the minimum load destroy my circuit? What does all that mean? Why does -12V have such a low max load? Thanks for any help you can offer.
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State Machine
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PostPosted: Thu Jul 20, 2006 7:51 pm    Post subject: Reply with quote  Mark this post and the followings unread
Quote:
Can I run a synth off of that? Will the minimum load destroy my circuit?


You can power a synthesizer, or anything you want, as long as your current draw off each rail (12, -2, 5) is within limits of the MAXIMUM current specified and above the minimum load current. As you pointed out, the -12 VDC supply is rather limited at 100 MA (0.1 A) so you will need to be careful to tally up your current requirements as you add modules. To add another twist, the MAX current is most likely derated to something less depending on the operating temperature.

Minimum load will not destroy your circuit, this just simply refers to the minimum amount of current that needs to be drawn from each supply rail in order to maintain regulation. What you need to do is this. If your circuits that you connect draw less than this minimum current, you will need to add a parallel resistor of proper value and wattage rating to meet the requirement. If you don't, the voltage will be typically lower than expected. To be abosolutly sure, just measure the NO LOAD voltage and make sure it's below the output rating.

Hope this helps ...
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zipzap



Joined: Nov 22, 2005
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PostPosted: Fri Jul 21, 2006 1:22 am    Post subject: Reply with quote  Mark this post and the followings unread
Quote:
voltage will be typically lower

will be (maybe much) higher - so watch your cabs!
It´s maybe possible to add another heatsink or powertranny to get more out of the -12v, depends on the transformer and design. Please don´t do anything like that unless you know for sure and feel safe about it!
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State Machine
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PostPosted: Fri Jul 21, 2006 7:31 am    Post subject: Reply with quote  Mark this post and the followings unread
Quote:
will be (maybe much) higher - so watch your cabs!


Yes, for sure there Very Happy My comment bears repeating then .....


Quote:
To be abosolutly sure, just measure the NO LOAD voltage and make sure it's below the output rating.


Good luck and check back if you need more advice marinosr

Bill
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