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Old 09 March 2010, 00:22   #41
cosmicfrog
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simple really
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Old 09 March 2010, 01:04   #42
8bitbubsy
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Ok guys
Took an old 486 AT PSU 200W... First I desoldered the switch and soldered the two main power wires from the switch wire to the power socket. I also soldered the fan to the +5v rail instead, to make it much more silent. After that I desoldered all the power wires inside it, then soldered the Amiga PSU cable in it
I also soldered a big wire from PG to +5v inside.. Now only the Amiga power cable sticks out of the PSU. I also resoldered ALL of the solder blobs on the PSU board, there were many dried solder joints....

Then I crossed my fingers and turned it on... No magic smoke!
Under load:
+12V: 11.90v
+5v: 4.76v
-12v: -11.27v

4.76v!

However, the A1200 boots just fine with Indivision AGA 1200, CF card, CF2PCMCIA adapter, floppy drive, Apollo 1240, Micromys adapter...
Paula works good too, playing some MODs atm in Hippo Player... Nothing funky going on.

EDIT: It's still running perfectly fine, should I still care about the low +5v rail..?

Last edited by 8bitbubsy; 09 March 2010 at 01:14.
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Old 09 March 2010, 01:13   #43
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Originally Posted by 8bitbubsy View Post
Ok guys
Took an old 486 AT PSU 200W... First I desoldered the switch and soldered the two main power wires from the switch wire to the power socket. I also soldered the fan to the +5v rail instead, to make it much more silent. After that I desoldered all the power wires inside it, then soldered the Amiga PSU cable in it
I also soldered a big wire from PG to +5v inside.. Now only the Amiga power cable sticks out of the PSU. I also resoldered ALL of the solder blobs on the PSU board, there were many dried solder joints....
That's definitely the way to do it. Nice, clean job!

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EDIT: It's still running perfectly fine, should I still care about the low +5v rail..?
If it ain't broke, don't fix it!
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Old 09 March 2010, 01:16   #44
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But I'm a perfectionist...
I'm also going to use this PSU on my new old stock escom A1200 that arrives tomorrow, I want NOTHING to make her in pain!

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Originally Posted by prowler View Post
That's definitely the way to do it. Nice, clean job!
I also cleaned all the flux in it with isopropanol alcohol, and made sure there were no shorts or any copper from a wire sticking out.. Pretty much a perfectionist's job
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Old 09 March 2010, 01:31   #45
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Really, I wouldn't know what to suggest you do about the measured 4.76V on the +5V rail. You seem to have done everything correctly and it doesn't seem excessively low to me.

There is no cause for alarm unless the voltage deteriorates, IMO. Keep an eye on the measured voltage and look for another PSU if that level isn't maintained.
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Old 09 March 2010, 01:35   #46
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Well, if I keep the amiga on for some minutes, they will eventually decrease .01-.02 volts...
Like 11.93 to 11.90, -11.30 to -11.27... 4.76v doesn't drop though.
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Old 09 March 2010, 01:35   #47
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Hey fellas,

I have an old pc PSU and would like use it for my Amiga 500 as the original is faulty .

I have tested the +5v on the PSU and it comes up strong with 5.3v but the +12v only reads 10.8v . How important is the 12v to Amiga ? Would this still be able to power up the Amiga or should I look for another PSU .

Cheers

have a read of this photo log =D
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Old 09 March 2010, 01:37   #48
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Well, if I keep the amiga on for some minutes, they will eventually decrease .01-.02 volts...
Like 11.93 to 11.90, -11.30 to -11.27... 4.76v doesn't drop though.
That's a good sign!
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Old 09 March 2010, 01:42   #49
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Ok I checked again, 11.90, -11.27, 4.76v... They don't decrease more than that. 11.93 and -11.30 at cold boot though.
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Old 09 March 2010, 01:44   #50
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Ok I checked again, 11.90, -11.27, 4.76v... They don't decrease more than that. 11.93 and -11.30 at cold boot though.
It's a good one!
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Old 09 March 2010, 01:49   #51
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I just heard someone here on abime saying that the +5v is can't tolerate big decreases/increases at all, so that made me thinking a bit... I also got told that the Apollo 1240 is VERY picky about the +5v, but seems like that's a myth! 4.76v and the Apollo is as stable as it can be.
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Old 09 March 2010, 01:51   #52
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A Power Supply is a game of two halfs,

for the most part its the Lack of Amps (current) that leaves our Amiga's underpowered and problematic, however one should NEVER underestimate under-voltage -

Although most expanded Amiga are happy to run just that little bit under 5volts, there are some devices that WONT like it at all..

my friend r0jaws recently discovered somthing very interesting with his modified BPPC and his BVision.

before the MOD the unit at 170mhz PPC and 50mhz 060 would play nice with mr BVision - all plu mbed up by a 200watt ATX -

Now after the MOD, the card runs flawlessly, however the BVision wouldn't have none of it... after some research my friend discovered that by plugging into an old A500 PSU the whole lot worked a treat.

This is because although the old PSU is weak on the AMPs its certainly got the voltages.

This is a good time to express the fact: At hight clock rates, the less tollerances become, IF you notice any problems, look toward the lowest common issue.


@8bitbubsy,

I must say dilligence is good, but perfectionism is infact an OCD, there are somethings that you really need to relax on.

you Amiga will be loving the clean (better part) of 5volts, especially when you start adding adapters / accelerators etc.
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Old 09 March 2010, 01:54   #53
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My Amiga is quite expanded... Guess it's not good after all then. Maybe I should try to find another AT PSU somewhere in my messy room.
Also, there's nothing wrong in perfectionism when you have a lot of time in your hands. I don't always do things perfectly, only if I have the energy and tools needed.
It's not like I'm forced by my mind to do things perfectly, it's just that I do care about old hardware
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Old 09 March 2010, 10:25   #54
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Quote:
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+5v + +5v = 10V

so I`m betting it gose to Ground

It ist 10V its 0V theres no potential difference, don`t know about the amps though
That has surfaced from the far recesses of my mind, I Did know something Once, that is before I became a frog

This is turning into quite a nice thread on amiga PSU`s wiki anyone

Perfection is over rated, been able to do something is far more important, well to me at any rate

8bitbubsy 0.3 volts under v5 whats that in percent%?
hehehe Forgoten How to do % calculations, someone help plz I get 0.015% or 0.035% both could be wrong or one could be right

so what have you got plugged in ->" Indivision AGA 1200, CF card, CF2PCMCIA adapter, floppy drive, Apollo 1240, Micromys adapter"

Least your 040 is stable, using CF card instead of HD saves a bit, Whats is Micromys adapter? if I get chance I`ll google it
So just Indivision AGA, CF2PCMCIA adapter, floppy drive and A1200 Mobo to use rest of the juice
Not to much there really if you compare it to what PC that power pack would drive, I could be wrong Its been known
Thanks for the Info and stuff Zetro

back to cleaning the pond out
cosmic

Last edited by cosmicfrog; 09 March 2010 at 10:41.
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Old 09 March 2010, 11:21   #55
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Very nice mod . I might leave some of the wires in mine and use it for the A590 power as well .
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Old 09 March 2010, 11:32   #56
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I might leave some of the wires in mine and use it for the A590 power as well .
If you have an A590, that would be a very good idea. Unfortunately, you would have to butcher the A590's PSU to remove the output plug and lead as well. Note that it is different to the A500 PSU's plug.

Also, I would not remove all the spare Molex conectors from the AT PSU, as they could be used to supply temporary power to an external CD-ROM drive or similar peripheral you might decide to hook up in the future.
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Old 09 March 2010, 13:25   #57
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My converted AT PSU measures 4.84v without the Apollo 1240 plugged in..
Is this normal..? With my 030 acc plugged in instead, it measures 4.80v....
With the Apollo 1240 connected, it measures 4.76v as written earlier.
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Old 09 March 2010, 13:35   #58
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It sounds like the +5V rail is struggling. Perhaps a larger proportion of the 200W rating is assigned to the +12V rail on your PSU than is usual.

You should really seek out a PSU with as high a rating on the +5V rail as you can find for use with the Amiga.
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Old 09 March 2010, 13:41   #59
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@cosmi

100% is 5volts

10% is 0.5volts

1% is 0.05

so a drop of 0.24 volts is (0.24/0.05) = 4.8% (within 5% tollerance) for most things thats perfectly fine.


As the car-insurance advert says..... "simples"
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Old 09 March 2010, 15:17   #60
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Quote:
Originally Posted by Zetr0 View Post
so a drop of 0.24 volts is (0.24/0.05) = 4.8% (within 5% tollerance) for most things thats perfectly fine.
So 4.76v (0.24v drop - 4.8%) is OK?
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