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Offline pyrreTopic starter

Questions about PSU's
« on: April 27, 2018, 03:39:52 PM »
I am making an ATX connector into a cable to use atx psu with amiga 500.

But i am a bit confused with the piouts.
+5V, +12V, -12V and ground i have sorted out.
HOWEVER
i am struggling with the shield connection.
is left untouched the amiga sound suffers badly
if connected to ground i get horisontal lines when ever cpu is doing anything. and strange artifacts on the screen....

What to do? how do i connect the shield cable properly?
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Offline TrashyMG

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Re: Questions about PSU's
« Reply #1 on: April 27, 2018, 05:56:18 PM »
Hmm, I just grounded mine without issues.

Cheap ATX supplies can be noisy... as usually a PC motherboard handles a lot of the smoothing.
« Last Edit: April 27, 2018, 05:58:26 PM by TrashyMG »
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Offline pyrreTopic starter

Re: Questions about PSU's
« Reply #2 on: April 27, 2018, 06:26:34 PM »
Quote from: TrashyMG;838771
Hmm, I just grounded mine without issues.

Cheap ATX supplies can be noisy... as usually a PC motherboard handles a lot of the smoothing.
yea... makes sense... there are very few components to smooth out any noise...

Then again... i had issues with the sidecar and buddha... turns out major problems was dirty edge connectors and one of the zorro slots in the sidecar being faulty....

the cf cards booted just fine under uae. bot not in the A500 before i swapped the zorro slot... now it boots just like it has never done anything but...

however... the artifacts and the horizontal lines are still there...
snd i dont know how to "get them away"....

at least i got to backup the cf cards in uae
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Amiga 1200 Tower Os 3.9
BPPC 603e+ 040-25/200, 256MBram, BVIsionPPC, Indivision AGA MK2.
Amiga 2000 (rev 4.0) Os 1.2/1.3
2088 bridgeboard, 2MB ram card, 2091 SCSI.
Amiga 500+ Os 2.1
Derringer 030, 32MBram, Buddha in sidecar, Indivision ECS.
Amiga CD32
Video decoder
 

Offline kolla

Re: Questions about PSU's
« Reply #3 on: April 27, 2018, 06:55:42 PM »
Modern ATX PSU are not so accurate regarding the 5V and 12V as that is mostly used for legacy"mechanics", spinning disks etc, and not so much for the motherboard electronics. Modern PC mobos run on 3.3V, so that's where they output "best quality" voltage.

Or in other words... avoid using modern ATX PSUs for Amiga, and instead go for dedicated new Amiga PSUs (there are quite a manufacturers), or all around good quality general purpose PSUs like the MeanWell ones.
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Offline Amiwest

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Re: Questions about PSU's
« Reply #4 on: April 27, 2018, 10:47:01 PM »
The A500 schematic I looked at has the DC gnd and the shield gnd tied together. If you have an external powered audio speaker system plug into a different outlet than the computer it can cause a gnd loop which can cause your problem.
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Offline pyrreTopic starter

Re: Questions about PSU's
« Reply #5 on: April 28, 2018, 05:04:32 PM »
Quote from: Amiwest;838785
The A500 schematic I looked at has the DC gnd and the shield gnd tied together. If you have an external powered audio speaker system plug into a different outlet than the computer it can cause a gnd loop which can cause your problem.
When i start a game. scorched tanks V.85 the psu screams like it is dying....

is there any way to reduse or remove the noise?
would soldering the shield to the psu case do any difference?
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Amiga 1200 Tower Os 3.9
BPPC 603e+ 040-25/200, 256MBram, BVIsionPPC, Indivision AGA MK2.
Amiga 2000 (rev 4.0) Os 1.2/1.3
2088 bridgeboard, 2MB ram card, 2091 SCSI.
Amiga 500+ Os 2.1
Derringer 030, 32MBram, Buddha in sidecar, Indivision ECS.
Amiga CD32
Video decoder
 

Offline x303

Re: Questions about PSU's
« Reply #6 on: April 28, 2018, 07:27:12 PM »
Maddi made a psu hack, not atx brick though: https://www.youtube.com/watch?v=TTSoVmBKXbM
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Offline pyrreTopic starter

Re: Questions about PSU's
« Reply #7 on: April 28, 2018, 08:06:22 PM »
Quote from: x303;838805
Maddi made a psu hack, not atx brick though: https://www.youtube.com/watch?v=TTSoVmBKXbM
Hmmmmm... interesting
I was aiming to put to use one of those pico psu's inside my amiga 500 powerbrick.
I have desolderd an ATX powersocket from a dead atx MB and soldered the amiga power cable to the atx socket. and it works wery nice. (apart from the noice, though)
if i can put one of those picos there and get rid of the noice... id be happy....

i even put a svitch to the power on leads on the socket.
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Amiga 1200 Tower Os 3.9
BPPC 603e+ 040-25/200, 256MBram, BVIsionPPC, Indivision AGA MK2.
Amiga 2000 (rev 4.0) Os 1.2/1.3
2088 bridgeboard, 2MB ram card, 2091 SCSI.
Amiga 500+ Os 2.1
Derringer 030, 32MBram, Buddha in sidecar, Indivision ECS.
Amiga CD32
Video decoder
 

Offline giZmo350

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Re: Questions about PSU's
« Reply #8 on: April 28, 2018, 08:15:04 PM »
Drewlio77 did a real nice brick transplant here.....

http://amigaworld.net/modules/newbb/viewtopic.php?topic_id=41790&forum=25
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Offline pyrreTopic starter

Re: Questions about PSU's
« Reply #9 on: April 28, 2018, 08:23:35 PM »
Quote from: gizmo350;838807
Drewlio77 did a real nice brick transplant here.....

http://amigaworld.net/modules/newbb/viewtopic.php?topic_id=41790&forum=25
Nice work. but im a bit worried that 65W is shortcomming of running a derringer, buddha, cd-rom and a zip drive....
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Amiga 1200 Tower Os 3.9
BPPC 603e+ 040-25/200, 256MBram, BVIsionPPC, Indivision AGA MK2.
Amiga 2000 (rev 4.0) Os 1.2/1.3
2088 bridgeboard, 2MB ram card, 2091 SCSI.
Amiga 500+ Os 2.1
Derringer 030, 32MBram, Buddha in sidecar, Indivision ECS.
Amiga CD32
Video decoder
 

Offline x303

Re: Questions about PSU's
« Reply #10 on: April 29, 2018, 07:19:16 PM »
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Offline pyrreTopic starter

Re: Questions about PSU's
« Reply #11 on: April 29, 2018, 11:10:04 PM »
Quote from: x303;838837
Not available yet, but coming: https://amigakit.amiga.store/catalog/product_info.php?products_id=866
That looks really interesting
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Amiga 1200 Tower Os 3.9
BPPC 603e+ 040-25/200, 256MBram, BVIsionPPC, Indivision AGA MK2.
Amiga 2000 (rev 4.0) Os 1.2/1.3
2088 bridgeboard, 2MB ram card, 2091 SCSI.
Amiga 500+ Os 2.1
Derringer 030, 32MBram, Buddha in sidecar, Indivision ECS.
Amiga CD32
Video decoder
 

Offline kzin

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Re: Questions about PSU's
« Reply #12 on: April 30, 2018, 12:13:03 AM »
try an electrolytic Capacitor between the 5v and GND, 2200uf 10v or larger should do make sure it is round the correct way, Try with and with out the shield connected. the lager the CAP the better.
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Offline dalek

Re: Questions about PSU's
« Reply #13 on: April 30, 2018, 08:22:31 AM »
Quote from: pyrre;838802
When i start a game. scorched tanks V.85 the psu screams like it is dying....

is there any way to reduse or remove the noise?
would soldering the shield to the psu case do any difference?

I'd try a different ATX power supply - sounds like it has issues.  If it's an old cheap ATX PSU it could have bad quality / failing caps.  Anything recent should be fine.
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