A7000+ PSU

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klintworth
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A7000+ PSU

Post by klintworth » Thu Aug 09, 2018 7:13 pm

Just received a Castle A7000+ from eBay UK. As I'm in Canada wondering if I can use the PSU on 110v. At present I'm using a step up converter to 240v with it. The back of the A7000+ PSU says 220v-240v. However I'm puzzled by the Acorn Product Brochure which says:
Screen Shot 2018-08-09 at 12.05.44 PM.jpg
http://chrisacorns.computinghistory.org ... n7000+.pdf
Anyone know If I can run it on 110v?
Thanks, Paul

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davidb
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Re: A7000+ PSU

Post by davidb » Thu Aug 09, 2018 7:45 pm

I would be slightly concerned that there might be a difference between the original Acorn units and those from Castle. I've never looked at the PSU in my Acorn A7000+ very closely. I seem to remember that it whines a little these days, so it would be something I'd think about replacing in the future.

Sorry not to have anything more concrete to suggest. :(

waltermixxx
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Re: A7000+ PSU

Post by waltermixxx » Sat Aug 11, 2018 11:07 pm

Maybe open up the power supply and look for a 110 v jumper...
The BBC switching power supplies had some links to switch it to
110...

You never know?

DigitalDunc
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Re: A7000+ PSU

Post by DigitalDunc » Sun Aug 12, 2018 11:23 am

Be careful with power supplies, they bite!

You might indeed find a link or switch but you will _also_ find a whacking great big capacitor across the rectified mains.

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1024MAK
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Re: A7000+ PSU

Post by 1024MAK » Sun Aug 12, 2018 6:02 pm

There are two main types of mains fed primary SMPSU (Switch Mode Power Supply Units):
  • Fixed input voltage types
  • Wide range multivoltage types
The wide range multivoltage types can normally run from any 90V to 250V, 50Hz to 60Hz mains supply without problems. They will only have a single large 400V or 450V electrolytic capacitor located near, or just beyond the bridge rectifier, which itself will not be far from the mains input connections. However, this arrangement is not definitive that it is a wide range multivoltage type.

The fixed input voltage types themselves come in two types, single supply types and selectable supply types.

The single supply types are only designed to work on the specified supply voltage. Typically 110/120V for USA and other countries that use this supply voltage, or 220V/250V for Europe and everywhere else that uses this supply voltage. They have no way of configuring them to work on a different mains supply. The 220V/250V type normally only have a single large 400V or 450V electrolytic capacitor.

The selectable supply types always have two large 200V or 250V electrolytic capacitors and a link/switch/jumper or PCB track to select the accepted input mains voltage. However, it's possible that a single supply 110/120V may also use two large 200V or 250V electrolytic capacitors.

By the way, applying 110V to a 240V SMPSU is very unlikely to cause any harm. It will either not start-up, not run, or only run with no load. If you try this, monitor the outputs to the load (computer) with a multimeter.

I hope this helps.

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
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DigitalDunc
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Re: A7000+ PSU

Post by DigitalDunc » Sun Aug 12, 2018 8:48 pm

An excellent and far more definitive answer than I was able to give, well done!

It did cross my mind that these power supplies, getting old, will need at some point to be repaired or replaced. Who might be undertaking such matters if anyone?

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