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#1 |
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Join Date: Apr 2009
Location: N/A
Posts: 962
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Amiga 1200 abnormal restarts
Hello, today I experienced something strange; when I switched on the A1200 this booted from the CF card and then as soon as it loaded Workbench it restarted. It then booted again, this time I could do some things but after some time it restarted again.
With another CF card it never booted in Workbench, keeping on restarting. Am I correct in assuming this is either power or capacitor related or it might be something worse? The reason I ask is that yesterday while trying to a CF card adapter I plugged this the other way round. Could this be the result of this mistake? i.e. - something got friend? My A1200 motherboard is Rev 2B with Blizzard MK4. If I disable the Blizzard MK4 everything loads fine. If I enable the Blizzard Mk4 and unplug the floppy everything looks to work fine too. That said up until a couple of days ago I didn't have any issue. |
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#2 |
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Join Date: Dec 2017
Location: Czech republic
Posts: 46
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How is your PSU performing? Has your motherboard been re-capped? Looking at sympthoms, the issue is most likely in the power circuits.
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#3 |
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Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 6,379
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Yep, sounds like a power issue. It could be capacitors in the machine, though it's unlikely they're directly the cause of the issue. Their leakage can however cause all sorts of problems as it corrodes the nearby tracks and components, so if that hasn't been done already, get it done now.
More likely the direct cause of the spontaneous restarts are the capacitors in the PSU. When they get old, they're less good at smoothing out the power, meaning you start to get more ripple and noise in the supply, some of which can trigger spontaneous instability or resets. Reducing power consumption will lessen the issue in this case, which matches what you're seeing. So I would have the PSU checked and recapped if necessary, or alternatively rebuilt with a modern PSU module. Before all that though, simple things: are you sure the PSU is connected correctly, and a slight movement of a loose connection isn't causing the reset? |
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#4 | |
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Join Date: Apr 2009
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Ok, have been waiting for too long to do this so I am planning to take my A1200 to technician some day this week. I just hope they'll do a good job.
Quote:
What is the best option to power up an A1200? It looks like using ATX power supplies will get me nowhere with this A1200... |
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#5 | |
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Join Date: Apr 2015
Location: Beauharnois,Qc,Canada
Posts: 227
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Quote:
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#6 |
Registered User
Join Date: Dec 2017
Location: Czech republic
Posts: 46
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Under what scenario did you measure the voltage? Flyback switched mode power supply only gives correct and steady voltage when under load.
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#7 |
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Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 6,379
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Indeed, the Amiga doesn't use enough power to effectively regulate with many modern ATX supplies, especially with many of them using the 12V rail as the primary output.
Also, where are you measuring the 4.8V? You could be getting a voltage drop due to tarnishing of the Amiga's power connector, for example. Try measure it at the ATX connector itself and see if it's 5V there - a drop of 0.2V due to poor connection quality is easily possible. |
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#8 | ||
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Join Date: Apr 2009
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I feed two 5V lines, one from an HDD connector coming from the ATX power supply and another from the floppy connector coming from the ATX power supply.
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I switch on the amiga and take the measure. Quote:
I get the reading from where I join the ATX connectors to the Amiga connector (the china-connector). Up to a month or two ago this was reporting 4.84V but now I get 4.8V. Could it be that dying capacitors are putting less request for power from the power supply? |
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#9 | ||
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Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 6,379
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Quote:
Quote:
Alternatively, adding hard drives and fans will also increase consumption and might be worth a try. |
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#10 |
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Join Date: Apr 2009
Location: N/A
Posts: 962
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I still have to get the new capacitors and replace these. However in the meantime I managed to get an old Amiga 500 PSU. I plugged the A1200 to this and it is running normally, boots immediately, no crashes.
How is the A500 power supply different from an ATX power supply? Also, I would like to take care of this PSU (my original A500+ poped a couple of years ago). Is there any maintenance I have to consider? |
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#11 |
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Join Date: Sep 2004
Location: Poland
Posts: 1,304
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For me it looks like PSU is losing parameters. How old is that PSU? If it's "old enough" You'll gradually lose parameters (sometimes until complete failure).
If it's a problem, better don't use this PSU. You can have problems with hardware, e.g. if power loss occurs while writing data on HD/CF/whatever. Last edited by Solo Kazuki; 14 January 2018 at 11:07. |
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#12 |
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Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 6,379
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There are a few different designs of A500 PSUs. Some are quite similar to an ATX supply, but less powerful and less sophisticated. They're made to use the lower power consumption of the Amiga, so their minimum loads will be well below what the Amiga uses. Other types are far more primitive, simple linear power supplies that don't have a minimum load, but are heavy and inefficient.
The main thing is really the capacitors in the PSU - these should probably be replaced in order to keep it working well... |
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