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110V-to-240V Astec power supply AA11040B/C question

T

TRS-Ian

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Hi, can someone please advise me if this works.

I have some 110V Astec AA11040B power supplies. The come in US Apples I import to Australia.

Today I looked in a 230V Astec AA11040C, from a local Apple ][ Europlus, it the power supply looks exactly the same PCB and componentry, just the wire which normally runs to 115V SEL post now runs to another place closer to the fuse.

Is this all that is needed to convert a AA11040B to a AA11040C or are there more internal changes to be made?

Thanks in advance,

Ian.
 
Maybe, yes, but you'd better post photos and check maximum voltage of the capacitors in the input stage.
 
I have found this doc when looking for info on the Profile powersupply and 110/240v support. I notice it has the schematic in it for the Apple II 1040B. There is no 1040C specific schematic. The schematic shows the 110/240v link, interestingly the parts list list's a 110/240v switch. Seems like they must have decided not to put a physical switch in. I have a 1040B supply, had not realised I might be able to easily switch it to 240v, so thanks.

http://bitsavers.informatik.uni-stuttgart.de/pdf/apple/power_supply/Astec_Power_Supplies_Aug82.pdf

/Rob
 
Hi Rob,
I've also performed this mod here in France. It works great. BTW, you also have to change the fuse.
Just take a look at this thread (sorry, french only but google translate is your friend !).
Finally, if not already done, change also the X2 capacitors : they will "explode" sooner or later.
 
Hello george,

Like shown on the pictures in the thread, the original fuse is rated 125V/2,75A. In an european PSU, it's rated 250V/2,5A.
So the fuse has to be replaced regardless of its state.

Antony
 
amauget said:
Hi Rob,
I've also performed this mod here in France. It works great. BTW, you also have to change the fuse.
Just take a look at this thread (sorry, french only but google translate is your friend !).
Finally, if not already done, change also the X2 capacitors : they will "explode" sooner or later.
Click to expand...


Thanks for posting, this mod works great. I live in Australia (240v) and I've got an Apple II Plus from the U.S. Before this I used a stepdown transformer for the Apple II+, but I did the mod, took all of 5 minutes. It's now running on 240v!

I have the Astec AA11040B power supply not the "C", but the mod is the same. I switched on the power supply outside of the Apple II+, to check that it didn't go bang, and checked voltages on the connector prior to putting it back into the machine. All voltages report correct after the mod.
 
amauget said:
Hello george,

Like shown on the pictures in the thread, the original fuse is rated 125V/2,75A. In an european PSU, it's rated 250V/2,5A.
So the fuse has to be replaced regardless of its state.

Antony
Click to expand...
Only an ignorant person would replace it ;)
 
I'm not sure why you are saying that. When you double the voltage you will want to lower the amp rating or otherwise you'll risk that the fuse isn't blowing when it's supposed to. Actually I'm surprised the specs only specifies a reduction to 2.5A - usually it goes much closer to half the 110V rating.
 
Tor said:
I'm not sure why you are saying that. When you double the voltage you will want to lower the amp rating or otherwise you'll risk that the fuse isn't blowing when it's supposed to. Actually I'm surprised the specs only specifies a reduction to 2.5A - usually it goes much closer to half the 110V rating.
Click to expand...
HINT: That's because you are thinking about average values of the electrical parameters...
 
I'm not sure I'm getting what you're hinting at. If you look at fused linear power supplies you'll find that indeed they usually do specify different amperage fuse ratings depending on how you set it (110V or 230V). That's what I would expect too. So I'm scratching my head here about what you actually mean.
 
Well, at 240 the primary rectification is going to be running in half wave mode so currents are not much different, just only present for half the cycle.
 
OK so a bit specific to the actual PSU design then - and adding to that the fuse presumably burns out due to total wattage and the lower-rated voltage may help there. I still would follow the manufacturer's specification for fuses.
 
paul said:
Well, at 240 the primary rectification is going to be running in half wave mode so currents are not much different, just only present for half the cycle.
Click to expand...
No, in both cases a two way rectification is used.
 
FWIW, similar Astec (and perhaps other brand) power supplies are fitted into more computers, so if anyone would import e.g. a BBC Micro from UK/Europe to the US, you can perform the same mod but backwards. It has also been documented online.
 
When switching between 110V and 240V the bridge rectifier and filter capacitors are configured either as a full wave bridge (240V) or as a voltage doubler (110V).
The run current would normally be halved for 240V, but the Inrush current might well be greater, hence the larger than expected fuse.
Chances are that for safety you should change the fuse anyway. It's probably a glass envelope without sand filling. These can simply plate the glass with evaporated metal when breaking on the sort of currents UK circuits can supply. This doesn't always break the circuit. You should use an HRC (high rupture capacity) fuse for all mains stuff in Europe.
 
Belated reply but I did the modification to two supplies and they worked perfectly. Also replaced the Rifa mains filter caps while I was in there, didn't change the fuse, and has been working perfectly for weeks.

Cheers everyone,

Ian.
 
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