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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: bburgy on March 26, 2007, 12:56:45 AM

Title: Amiga 1200 Startup Issues
Post by: bburgy on March 26, 2007, 12:56:45 AM: Hi all,

I have an Amiga 1200 with a bit of a problem. When I power it up, sometimes absolutely nothing happens. The power light will come up, and maybe the disk drive will utter a single grunt, and then nothing happens at all.

Other times, the floppy drive will move once, and the hard drive will begin to spin. The hard drive light will not so much as flicker.

Then, on the rare occasion when it wants to work, the hard drive light will finally flicker and the system will boot.

I'm not sure what the problem is. I've replaced the original Seagate hard drive with a working IBM drive that came from an old laptop (which I confirmed is working before installing it). The problem persists.

The computer will not even so much as boot from a floppy during the times when it doesn't work as normal. When I hook up the video, I see a couple of flashes and then nothing. It's as if the kick start doesn't even... well... start.

Anyone have any ideas?

Thanks!
Title: Re: Amiga 1200 Startup Issues
Post by: Amiduffer on March 26, 2007, 01:13:11 AM: Hmm. Sounds like a badly worn out PSU, and they are underpowered to begin with. I think Amigakit has some new ones available.
Title: Re: Amiga 1200 Startup Issues
Post by: bburgy on March 26, 2007, 01:35:32 AM: Thanks for the reply.

I should have also mentioned that at one point I had run the A1200 on a custom built adapter that was hooked up to a PC power supply (which was fairly new at the time). The issue existed before, during, and after, unfortunately.
Title: Re: Amiga 1200 Startup Issues
Post by: rkauer on March 26, 2007, 01:54:32 AM: Could be a faulty floppy drive. Or a bad cable (check both: IDE and floppy).
Title: Re: Amiga 1200 Startup Issues
Post by: da9000 on March 26, 2007, 05:31:02 AM: What color are these flashes?
Title: Re: Amiga 1200 Startup Issues
Post by: Bamiga2002 on March 26, 2007, 08:24:46 AM: Check the proper seating of the ROM chips, try re-seating them.
Title: Re: Amiga 1200 Startup Issues
Post by: spirantho on March 26, 2007, 10:31:18 AM: If it doesn't start up immediately, try just leaving the machine on for a few hours and see if it eventually boots up.

If so it may be a problem with the power regulation capacitors - I've had two 600s like that. It's an easy fix if you have the right capacitor and a soldering iron.

Does the Caps Lock light stay on?
Title: Re: Amiga 1200 Startup Issues
Post by: da9000 on March 26, 2007, 06:21:50 PM: Quote

spirantho wrote:
If so it may be a problem with the power regulation capacitors - I've had two 600s like that. It's an easy fix if you have the right capacitor and a soldering iron.

Is the purpose of leaving it on for a while to get the regulation caps to warm up, or something else? (what was wrong with yours? leaking fluid/bulging? or something else?)

Thanks
Title: Re: Amiga 1200 Startup Issues
Post by: bburgy on March 27, 2007, 07:42:26 PM: When the screen would flash, it flashes white for an instant, a couple of times.

It could be the floppy, I suppose. Once I boot it up, the drive does work fine though.

I'll try reseating the chips once I get home.

The caps lock light never turns on -- one time the keyboard ribbon cable was clipped accidentally during installation, and from that point on the caps lock light never turned on. The rest of the keyboard worked, however. I assume that's what caused it :P

I've tried leaving the Amiga alone while it's frozen for a few minutes. Nothing has happened. I'll try leaving it on longer. What sort of capacitor do I need? And where can I find it to replace it on the mother board?

Cheers!
Title: List of capacitors
Post by: rkauer on March 27, 2007, 08:06:47 PM: Don't suffer: change all the caps. Costs less than US$9.00!

Here comes the "shopping list":

18 caps (all electrolitics)

3 units 10Uf x 16 volts SMD

5 || 22Uf x 35 Volts SMD

2 || 47Uf x 16 Volts SMD

4 || 100Uf x 65 Volts SMD

2 || 470Uf x 16 Volts Regular size

2 || 1000Uf x 10 Volts Regular size

Be happy!

"God must love idiots, make a lot of them!" (Mark Twain)
I personally wonder if Mark knows about Microsoft users...:-D
Title: Re: Amiga 1200 Startup Issues
Post by: motrucker on March 27, 2007, 08:41:14 PM: It does indeed sound as if you have a bad cap. or two. Or a bad connection somewhere.
This may take much checking with a multimeter.
Title: Re: Amiga 1200 Startup Issues
Post by: bburgy on March 29, 2007, 03:50:24 AM: Sounds like I have a job ahead of me. Is it possible to get my hands on the schematics of the Amiga 1200's motherboard somewhere? I think that may be quite helpful.

Thanks!
Title: Re: Amiga 1200 Startup Issues
Post by: da9000 on March 29, 2007, 04:05:30 AM: You don't really need the schematics to change the caps. Just good soldering skillz :-) And also make sure you get the right parts! And get the polarity right when you solder the caps.

I don't know if there are A1200 schematics floating around, but there must be some...
Title: Re: Amiga 1200 Startup Issues
Post by: bburgy on March 29, 2007, 02:14:07 PM: For anyone who is interested, I think I found a link to them on this site:

http://www.amiga-hardware.com/showhardware.cgi?HARDID=13