I've begun a project to change the PSU of my IIGS to accept 220V directly. This project is based on Drew Biegs' solution. Read about my project and see a few pictures here.
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I think it is stupid to destroy an authentic working //GS supply in this way! BTW the aluminium boxed //GS PSU's can be switched to 220V by cutting only one connection/wire...
If switching a IIGS PSU from 110V to 220V would be that simple, you'd think there would be at least one article about it in the internet, wouldn't you? On the contrary, I've found dozens of sources stating that the 110V only PSU cannot be turned to 220V. The European IIGS PSUs are switchable but mine's a US one so that's not an option for me.
And about "destroying" the PSU, the IIGS aren't exactly rare, so I see no harm in modifying one, if it's done nicely. And mine's completely reversible in case I for some reason need to get it reversed, which I doubt. Besides, with an almost thirty years old PSU, you'll never know, when it's going to kick the bucket.
You use your IIGS the way you like, I'll do the same.
I never had to use internet articles to convert a couple of //GS PSUs, instead I used my thinking. Do I have to write an article as yours on the internet for every soldering I make? I would have been a writer then...As long as something is no longer produced consider it rare.
I'm sorry, did you say that you have a solution for Protek's problem?
If so; why don't you share it with the community?
How about this: let us think outside the box (in more ways than one).
Why not use a Buggie power supply that has one of those 110V/220V switches on the back...?
Problem solved. No destroying a "sacred iigs power supply" and no buying any Mean Well PT65B power supplies and then adding a voltage regulator circuit.
I agree with Insanitor, adapt a modern PSU that already accepts 220. The challenge I have found with this, however, is that one may need to further regulate the output before feeding it directly in to the GS logic board. Modern day PC boards have additional filtering built-in, whereas most older systems relied on the power supply to do it all.
When I jury rigged a MiniITX PSU into a GS, I did not do this, and though it works pretty well, it's not exactly the most stable. I think something relatively simple like placing capacitors on the +5 and possibly the +12 lines between the PSU output and the logic board might be along the lines of what needs to be done, but I am only half an idiot when it comes to electronic circuit building, so please someone else more educated suggest something.
Regardless, I think the point is that it might actually be easier and/or safer to 'clean' the output of an adapted modern PSU rather than modify the input on a 'vintage' one that was never designed to do 220. (Unless someone knows a secret that he'd like to share with the rest of the class?)
I am not entirely certain about older power supplies, but the newer ones have very good voltage regulation.
The problem with using a newer power supply is this:
Wikipedia says, "Pin 20 (formerly −5 V, white wire) is absent in current power supplies; it was optional in ATX and ATX12V ver. 1.2, and deleted as of ver. 1.3.".
So, what must be done to overcome this problem is to add a -5v voltage regulator to the -12v rail and that, along with a capacitor, will give you all the voltages you need to power up an Apple ii.
I would gladly do this, Steven.
But right now I am abroad for a month but even if I were at home it wouldn't help much because I have sold those two //GS machines I converted on ebay (I regret now a bit for that not because of PSUs). I kept the ones with astec PSUs which at the time I thought were a bit more powerful PSUs and were produced by a better company. Anyway if somebody provides photos of the components and solder side of the PCB of the 699-0126 PSU near the input stage I should be able to point out the wire that should be removed. Though it was quite trivial - the voltage doubler in the input stage should be switched/converted to two-way rectifier by removing a single wire...And I would have removed those notorious filter capacitors since under 220V mains supply they are exposed to doubled voltage (though they are rated at 250V but they tend to burn even under 110V AC).
I don't know, if I have the correct type of PSU as the filter capacitors in mine are rated only at 200V but as I conveniently have the PCB out of the casing, I took pictures of it from both sides. Is the type number on the casing or the PCB itself?
My IIGS PSU seems to have the same type number as Georgel mentioned in his posting. Nevertheless, the filter capacitors in mine are rated only at 200V as I said in my previous post. But if you need pictures of the PCB, drop me a note.
For what it's worth, the new PSU is now securely in the casing and it gives correct voltages to correct pins. The PSU is now reassembled and externally indistinguishable from an unmodified one. The IIGS boots and works all right. There's now one brick less on the floor.
Next task is to open up the genuine LiteOn PSU of my Amiga 4000 and do a capacitor overhaul.
There are a number of medical power supplies that have the correct voltages and will fit inside a IIGS power supply case. here
I am wondering. If someone could really convert a 120V iigs power supply to one which can take a higher input AC voltage, is this really the ultimate goal? Would it not be prudent to check and/or replace all of the electrolytic capacitors inside the power supply after conversion...?
I looked into it previously but couldn't really find any definitive quidelines for modifying the primary side of the PSU to accept higher voltages. I think that if it was simply a matter of taking all the components on the primary side and changing them to ones with higher ratings, someone would've done it. I think in reality you'd have to redesign the whole power supply.
I'm not also quite sure about the regulations regarding modifications directly involved with mains voltages done to the electric appliances. There is a high risk of electric shock or fire, if you're not absolutely sure what you're doing. At the very least you may end up with a dead appliance.
SpeedyG's documentation about the Apple II PSUs was very enlightening to me and that's why I ended up replacing the PSU inside the casing.
My last post in this thread has a link to a file which contains pictures of that power supply.
I would REALLY like to see this miraculous one wire modification.
This topic grabbed my interest as I too have a IIGS with a 110v power supply that I wanted to come up with a 240v solution for. I think Georgel's comments seemed a bit blunt to me initially. But then when you think about it, we seem to be saying if there is not an article on the internet, it cannot be done. His point was we should all have a look and think for ourselves sometimes rather than do the quick google and if we find nothing leave it there. Good to remind us Georgel.
Anyway, back to the powersupply. I have attached photos of my power supply. In the photos, there is a hand drawn schematic of the input circuitry. Looks like in this power supply, it is using what SpeedyG's power supply pages says is a doubling of the input voltage (refer his very useful PS pages, picture4) setup. If you also compare to other apple power supplies, apple ii and apple iii, they all have similiar input stages. There is a convenient wire link in my DynaComp IIGS PS that if you remove/cut, this is the same as the 110/220v link in the other supplies.
I did this mod, and it seems to work ok.
I have some questions regarding voltage ratings in the filter capacitors, maybe Georgel or Speedyg can comment on these. The 0.22 uf AC ones have 250~ voltage rating in this. These would be running close to the limit, are these ok do you think?
and then the 100uf filter caps have a 200v rating on them, do you think these are ok?
Any comments are most welcome from anyone on this.
Yes, that's the modification. You can leave the 220nF filter capacitors. Even if they blow it will not hurt the PSU or computer themselves, though the stench would be awful But as well you can simply remove both capacitors without any replacement.
rjustice: Thanks for sharing the modification with us! It's true that we shouldn't just rely on what's available in the internet. On the other hand, without sufficient base knowledge, meddling with electronics may very well result with dead hardware. I, for instance, have no educational background in electronics. All that I know I've pretty much learned myself and I'm not shamed to admit that what I know is pretty rudimentary. Nearly not enough to start meddling with something that involves mains voltages.
I did read SpeedyG's wonderful documentation about principlec of PSUs and also made notice that in many cases it's not possible to modify a 110V PSU to accept 220V. The IIGS PSU in question seems to be an exception. Nevertheless, were I to do the modification to my own, I'd replace at least all the capacitors on the primary side rated to withstand 240 volts. For example, the two big capacitors on both sides of the jumper in question is rated only for 200 volts. I may be wrong but that's what my knowledge and common sense tells me. I also don't know about the life expectancy of an Apple IIGS PSU but again common sense tells me that an almost 30 year old PSU is probably not in its prime any more.
Well, I still have the original PSU. If I ever feel the urge to restore my IIGS to near original condition, I'll definitely use this information as my reference.
No problems Protek, appreciate your comments and point of view. As a forum, if we can help each other out, that's the best result.
For the big capacitors, I think these should also be ok. A bit of googling to refresh my rusty memory leads to 240v rms generating a peak voltage of approx 340volts (240/.707). This is then split over the two caps each rated at 200v, so 400v total. So 340v is within the 400v total.
A little update on my side. I restored the PSU back to factory condition and did the jumper wire removal. The main reason I did this because the circuit that converted -12V down to -5V in my modded PSU wasn't very good. The wires are soldered back to the old PSU. Still need to double check the connections and put it back together before firing it up (disconnected from the IIGS, of course).
the pictures unfortunatly don't display some aspects of the used parts...
but at least some basic scetch might help ahead:
there are some remarks to the topic:
It's far more easy to design a PSU that offers a "step down" from 220 Volt to 110 Volt
than the otherway around from 110 Volt as "step up" from 110 Volt to 220 Volt.
The main reason: while stepping down you can be sure that limits of the compoinents
won't be exceeding while otherway around the lower limts might be exceeded by "stepping up".
the connection at the bottom where C3 and C4 meet there is the groundingpoint of the
In general i'd agree with all told here...
but even without knowledge of several other parts of the circuit the one critical part
Q1 the power switching transistor
If you intend to change the limits you must confirm that this
transistor is able to handle at least 450 Volts.
Therefor you should read the front of that transistor and then
check the data in a transistor databook.
[quote]insanitor wrote:[quote=georgel][quote=gsmcten]georgel, I'm sorry, did you say that you have a solution for Protek's problem? If so; why don't you share it with the community? Steven :)[/quote] I would gladly do this, Steven. But right now I am abroad for a month but even if I were at home it wouldn't help much because I have sold those two //GS machines I converted on ebay (I regret now a bit for that not because of PSUs). I kept the ones with astec PSUs which at the time I thought were a bit more powerful PSUs and were produced by a better company. Anyway if somebody provides photos of the components and solder side of the PCB of the 699-0126 PSU near the input stage I should be able to point out the wire that should be removed. Though it was quite trivial - the voltage doubler in the input stage should be switched/converted to two-way rectifier by removing a single wire...And I would have removed those notorious filter capacitors since under 220V mains supply they are exposed to doubled voltage (though they are rated at 250V but they tend to burn even under 110V AC).[/quote] My last post in this thread has a link to a file which contains pictures of that power supply.
http://www.applefritter.com/content/apple-iigs-power-supply-problem-essayduneI would REALLY like to see this miraculous one wire modification.[/quote]
I had an old ATX PSU a couple of months ago and it was rebuilt. I added a negative voltage regulator inside the PSU converting 12V to 5 V and modified the ATX connector to fit my AIIGS connector. Thus, a new PSU is actually outside the AIIGS - the pdf materials:
Up to my knowledge, only Dynacomp IIGS PSU can be easily converted by just removing one wire like shown on this picture : I've compared 110V and 220V Astec PSU. There are many differencences on several components in the primary section : R48, R5, R8, R3, R45, C1, C3 and C4. By the way, you can purchase a dissertation introduction online
Spam link deleted - Tom
Interesting. The link spammers are becomming more and more sophisticated. Of course, the "lilylite" account was only created to promote the link spam to this "purchase a dissertation" website. The first part of the message text was simply copied 1:1 from another forum:
and kind of seems to make sense in this thread, as the message text looks very related - of course hoping, it would disguise the link spam, so it will be missed by an admin and not be deleted. If that was a fully automated link spam attack, than that's surprisingly sophisticated.
Wowowow. AI are learning too fast.
I'm converting that to a hot URL:
In your post, it was not tagged with <a href> so it is a cold URL.
Spam link deleted. I'm leaving the spam post, as I think it's interesting.
haha... that so interesting to keep. lol
Here's a .jpg of a 220VAC schematic, with a 400VDC filter cap on the bridge rectifier.