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Old 20 July 2020, 16:01   #1
joora
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Amiga 1200 problem with soft reset (and hard reset)

Hi all,

I have recently obtained a nice Desktop dynamite 1200, which was supposedly recapped. The seller mentioned intermittent problems to booting into kickstart 3.1, and they're present, but I would like to make this Amiga work flawlessly, so I need your help.

The Amiga boots up fine and loads floppies without any problems.

Upon soft reset, the screen freezes, often changes to one color (which is usually the background color of the program/game running (etc. blue for lemmings, purple for kick 3.1 screen) or stays black and nothing happens. However, if I soft reset again after some time (like half a minute or minute) it will reset normally and happily boot to kickstart 3.1 screen.

I can try to reset however many times I want in the short time period, it won't work. So, my best guess it's time related - it must pass some time period between the initial reset and the repeated reset to work.

I've briefly tested, but it's the same with the hard reset (switching off the PSU) - if I switch on after a couple of seconds it won't boot (black screen), but if I wait for a while (minute or so) it will boot normally.

Does anyone have an idea what could be the problem, as I would like to make the amiga work properly?
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Old 20 July 2020, 16:46   #2
solarmon
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Check that the reset signals are getting to the various chips correctly.

https://sites.google.com/one-n.co.uk...-reset-signals

https://sites.google.com/one-n.co.uk...-reset-signals

Use amigapcb.org to locate the chip, pins and signals. It is best to use a logic probe to observe these reset signals.
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Old 20 July 2020, 20:02   #3
joora
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Quote:
Originally Posted by solarmon View Post
Check that the reset signals are getting to the various chips correctly.

https://sites.google.com/one-n.co.uk...-reset-signals

https://sites.google.com/one-n.co.uk...-reset-signals

Use amigapcb.org to locate the chip, pins and signals. It is best to use a logic probe to observe these reset signals.
thanks on the quick reply. However, those actions are above my abilities

Is there anything else I could try to diagnose the problem before sending it for repairs (and additional expenses)?

Some other observations:
- on reset attemts, Caps Lock blinks once.
- amiga was once fitted with HDD (stated on the box), which was obvously taken out
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Old 21 July 2020, 10:01   #4
cpiac64
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Amiga load in ram some data like rad: and patch, this data resist short reset and sometime conflict if the short time is too short or ....

verify if is recapped

sorry for my bad english
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Old 21 July 2020, 10:12   #5
solarmon
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The only other basic things you could do/check:

* Reseat the Kickstart ROM chips - inspect the pins and sockets, clean with isopropyl alcohol.
* Check power supply (under load) - check 5V and 12V rails with a multimeter - see http://www.ianstedman.co.uk/Amiga/am..._supplies.html

But it sounds to me there are possible motherboard issues that need further investigation and repairs.
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Old 21 July 2020, 10:13   #6
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Oh, and do you have any expansion cards in the A1200? If so, remove them and see if the same behaviour occurs.
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Old 21 July 2020, 10:53   #7
Hedeon
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Can be some resident program running amok. It (or just the pointer) can survive a few seconds without power. (what cpiac64 says).
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