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Old 08 January 2019, 01:45   #21
Stedy
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Hi,

Can you check the Power Good signal on the ATX adaptor?
What you describe matches the symptoms of an invalid POWER GOOD/power on reset which the A4000 needs to start up correctly, this is essential for a defined, orderly startup.

The Power good signal in an ATX system will be low (<0.8V) for 0.5 seconds on power on, then should go high, once all supplies are stable. You should see this with a multi-meter.
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Old 08 January 2019, 01:50   #22
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Thanks, that's some great info! I'll check it tomorrow when my friend turns up - he's bringing stuff to test it out.
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Old 08 January 2019, 01:52   #23
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Quote:
Originally Posted by Daedalus View Post
But it might be worth trying to find a PSU that only gives maybe 150-300W of output. Just make sure that the 5V rail isn't too low as that's the important one for an Amiga.
What is considered too low on the 5V rail? I have a new CS350 watt PSU as well and the problem is the same. I even got some older ATX 350 watt PSU's which I've tested and that's the same as well.
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Old 08 January 2019, 01:58   #24
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It's a bit hit or miss, I'm using a Corsair CMPSU-400CX with my A1200 tower and it works great. It seems to have very good stabilisation on all the rails.
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Old 08 January 2019, 02:01   #25
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Generally Corsair has a great reputation with their PSU's so that's what I usually choose. I'm not sure about the CS series though - apparently that's their lowest quality line and it hasn't had good reviews as such. But I read that after having purchased it.
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Old 08 January 2019, 02:07   #26
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Quote:
Originally Posted by Englyst View Post
So what can I do? It's not like A4000 spec'ed ATX PSU's are easy to find by the sound of this. Any suggestions as to what would work as a Mediator ATX PSU?

The Corsair CS550M is my current go-to for towerized A4000s, works well, though this is EOL'ed. Apparently the TXM series replaced it, I can't recommend that though as I haven't tested them. Stay away from the CXM and GSM series though.

Quote:
Originally Posted by Daedalus View Post
I'd suggest maybe loading the 12V rail with some sort of dummy load, like a stack of old hard drives or big 12V fans. For a more permanent solution, a high power rated resistor attached to the chassis and connected across the 12V rail can do the job as well, but ultimately you really need to know the minimum draw requirements for the PSU. Maybe ask the manufacturer for the full datasheet. In general, the lower the maximum capacity, the lower the minimum load, though this isn't a hard and fast rule. But it might be worth trying to find a PSU that only gives maybe 150-300W of output. Just make sure that the 5V rail isn't too low as that's the important one for an Amiga. An alternative is to use an industrial PSU module instead of an ATX supply, but that requires a good deal more work for the modifications needed.

There could of course be some other issue happening, not actually related to the PSU... But the PSU seems the most likely.
I tried this with the SF450 in a Desktop A4000, thinking loading the 12V might kick up the 5V higher, it didn't work out. Tried a big stack of fans and HDDs(with just the motor spinning) and plugged in a whole 120W SFF computer to one of the 12V headers on the power supply, it didn't help at all in that the 5V didn't go up at all. Though I was only adding another 150W load or so to the 12V rail. Not saying this can't work, but I couldn't find a practical way of doing it. Some suggestions like adding an automotive light or two, or a gigantic string of LEDs was not to my taste-I know just being a sissy, but this had to work in real life.

Though the SF450 eventually worked out in my Desktop and my problems were elsewhere, just that the blah blah blah-broken record.

Last edited by grelbfarlk; 08 January 2019 at 02:20.
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Old 08 January 2019, 15:38   #27
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@Englyst

Yes it also has P9 connector on it.
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Old 08 January 2019, 15:46   #28
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Thanks! Will keep that in mind when I choose one, if needed
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Old 09 January 2019, 01:12   #29
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Quote:
Originally Posted by grelbfarlk View Post
I tried this with the SF450 in a Desktop A4000, thinking loading the 12V might kick up the 5V higher, it didn't work out. Tried a big stack of fans and HDDs(with just the motor spinning) and plugged in a whole 120W SFF computer to one of the 12V headers on the power supply, it didn't help at all in that the 5V didn't go up at all. Though I was only adding another 150W load or so to the 12V rail. Not saying this can't work, but I couldn't find a practical way of doing it. Some suggestions like adding an automotive light or two, or a gigantic string of LEDs was not to my taste-I know just being a sissy, but this had to work in real life.
Yeah, it's not at all guaranteed to fix any PSU regulation issue, but it's common enough and I've used it to (temporarily) solve it for a few PSUs myself. The design of the PSU plays an important factor too - sometimes the 3.3V and 5V rails are on one supply and the 12V rail is independently regulated, meaning you need a minimum load on the 3.3V or 5V rail instead to get the 5V output stable.

Any PSU that I've found with regulation issues typically only needed around 1-2A of current drawn on the main rail to regulate. This is achievable easily enough with a high wattage resistor for as neat a fix as you're going to get, and the chassis can be used as a heatsink if necessary.
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Old 09 January 2019, 12:22   #30
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I'll keep this in mind if we need to go that way. Thanks!
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Old 09 January 2019, 19:59   #31
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Daedalus is correct about the load rating on the rails. When I updated the PSU from 350 to 550 on the BPPC Amiga, it didn't boot. The moment the 350 was reintroduced, it booted. Try an older ATX PSU 250 to 300 should be enough.
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Old 09 January 2019, 20:24   #32
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I have already tried 3 different 350W PSU's and no change. All components have been swapped, except for the ATX power converter and still no change. I remember it just suddenly stopped turning on at some point in the past.

When it's up and running it works fine. Been running for the last 2 days without issues. When turned off, the problem turning it on again rears it's ugly head. 1 out of 20-40 times it does turn on properly.

My friend tested the ATX power converter and thinks the chip on it is faulty. I'm getting a new one tomorrow and we'll change it and see what happens. It only costs 0.4 EUR so that's a cheap fix if it works. The POWER_GOOD line didn't drop after it went high most of the times we tried, so that's why we're changing the chip.

I'll write back with the result as soon as he's changed the chip out.
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Old 09 January 2019, 20:25   #33
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just FYI on corsair many of those lower watt supplies are made by CWT and Great Wall
also some get there 3.3v/5v from 12v rail
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Old 09 January 2019, 22:17   #34
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What chip is on the board? If it's a simple logic IC, it might not be debouncing the power switch input sufficiently, resulting in erratic power on/off behaviour. The ATX spec specifies that PSUs should have a certain tolerance for switch bounce, but in my experience, many don't and rely on that function being provided by the controlling circuit.
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Old 10 January 2019, 11:13   #35
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It is a simple logic IC from Texas Instruments:

https://www.mouser.dk/ProductDetail/...GyZpKqrZ5lw%3d
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Old 10 January 2019, 11:37   #36
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Hmmmm... well without hooking it up to a scope I can't say for sure, but it probably isn't helping matters anyway. If the PSUs don't have particularly robust debouncing, you could get essentially random behaviour when using the power switch. However, even if that is a problem, it should still stay on and be stable when it does manage to latch, and should be able to turn it on more frequently than 1 in 20 times. It'll be interesting to see if changing the chip makes any difference...
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Old 10 January 2019, 11:39   #37
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It sure is stable once it's running, it's just hard to get it to that point
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Old 13 January 2019, 13:06   #38
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I'm putting the project on hold for a little while - now the power converter flips out totally by turning the machine on and off all the time. And also the PCI cards apparently didn't get enough power via the P9 plug (I assume that's what it's for) since they either malfunctioned or disappeared. Had the Voodoo in there (no system memory from it and couldn't get a signal out) and the netcard disappeared, or the Voodoo card disappeared.

And on top of that, my friend who should fix the ATX converter, got sick with pneumonia and went to hospital.

So I guess the next update is when I have moved, and got a new ATX power adapter.

Thanks for all the comments here.
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Old 03 August 2019, 14:16   #39
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Finally an update as to where I stand with this:

Got a new PSU (EVGA G2 Supernova 550W), the smallest I could find on EVGA here, and it works! Modular too, so small amount of cables in the cabinet.

Apparently My Ami was not fond of Corsair PSU's.

Got my Voodoo card working as well, except memory on it are not allocated to the system. So I've ordered a new driver CD from Elbox (dang expensive for a CD!) and hope that is what will fix my few problems with the Mediator (a rev 1.0 of the A4000d Mediator board).

Network card is not getting recognised (Realtek 8139C Fast Ethernet card) but it's available in the listing from PCIinfo.

Getting a lot of #80000004 crashes (AHI Prefs, copying from Dopus4) and tried different 68040.library versions with no luck. Memory errors perhaps? Will check that later.

So it's moving forward and hoping everything will solidify into a great A4K at some point.

I'll update the thread with solutions as I go, in case someone finds this valuable.
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Old 04 August 2019, 05:59   #40
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I'm a bit late to the thread, but I can see how frustrating this has been.

I had an Elbox tower bought new about 6 years ago with the Mediator for my A4000. It was supplied by Elbox with a power supply. I don't recall if it was a problem initially, but in my later usage I found the system would require multiple front power button pushes to power up or turning it off could only be done with the rear power supply switch (the front power button would often just reset the system).
I know this doesn't help you now, as you seem to have solved the problem....but it seemed to me either the power supply wasn't suitable for the system or the ATX>Amiga board wasn't a great design. With my system because the way the Mediator was powered it would have been some work to modify an alternate solution.

I have had a few Mediators over the years and they are a pain in the butt to get working, but always finally found a stable setup once working - at times it would be easy to screw the install up with some new software installation. Setting them up step by step and backing up the whole OS setup each step was the least frustrating way I found of installing them.

I've recently found some 8000 0004 and 8000 000B errors related to memory. I've never been able to identify the 680x0 libraries to cause me trouble, but I found especially with the A4k/Mediator and 68060 that the OS 3.1.4 and associated ROM did seem to make the system more stable. Maybe worth a try?

Let us know how you get along!
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