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Old 10 January 2005, 12:23   #1
Galaxy
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A1200 colour problems

I have just acquired an A1200 but the colour is wrong - Hues of blue are not displaying. This is only present when connecting up via the RGB connector - colour is correct when using the modulator. So I suspect the connector.

I can rule out any problems with the monitor or cable.

The RGB connector looks very clean, and there are no bent or missing pins. I have tried plugging and unplugging the monitor several times, so I doubt bad contacts. I think that it is some time since the machine was used as the HD did not spin up on first power on.

I am yet to open the machine up, but I was wondering if anyone had come across similar problems. Any suggestions would be welcomed.
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Old 10 January 2005, 20:45   #2
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Hi Galaxy - try looking at the bottom of the PCB (of the Mig, of course), sounds like a classic "dry joint" to me. A dry joint is where the solder didn't make a reliable connection to the items being soldered. Classic causes are: Too cold a soldering iron, dirty components to solder, poor quality flux, items moved whilst solder cooling.

Easy to cure a dry joint, just re-apply a soldering iron to the joint and make sure the solder flows properly - if not, re-solder. So, in your case - assuming we're talking of a 23 way D socket soldered to the Amiga PCB (as opposed to a graphics card). Simply dis-assemble the Miggy, lay the mobo out on your work bench (the wooden variety :>) and apply your soldering iron to each joint made by socket/PCB, making certain you don't bridge any pins.

The HD on my 1200 never spins up right away - have to always reset the mig to make it boot from the HD on first power up.

Electrolytic capacitors age (obviously with time), so it could be that since your Amiga hasn't been powered for a while, some of the electrolytic capacitors had to be "re-formed" - a process by where the insulating layer between the plates has broken down due to time, and gets remade by the reaction of electricity, electrlyte and the aluminium foil used to make them. For a very short period of time therefore, your old capacitors could be acting as a short circuit and causing all kinds of problems. To avoid this, simply power up your Amiga once in a while - even if only for a few minutes. This will ensure the capacitors get a regular "reforming charge" - they will live longer as a result.

One thing for sure, if it was a ZX Spectrum we were talking about, I could (and would offer) to fix it for you.
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Old 10 January 2005, 21:12   #3
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Thanks for the tips Lloyd, I'll look in to it.

As for the HD spin up, have you got a 2.5" or a 3.5" drive. In my working 1200 the HD has never spun up on time from a cold boot as it is an older 3.5" (some of which have longer spin up times). If you have a 2.5" drive though it should be quick enough.
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Old 10 January 2005, 21:41   #4
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Yes, it's a 2.5" drive, IBMH2258-A3 256Mb capacity. Have a 4.5 GB SCSI HD (and a Teac CDR drive) attached too - thanks to you for supplying the Squirel driver disk.

As long as power is on, the Mig will boot from the HD, but every cold boot needs the Mig to be re-booted as it falls back to the "insert disk" screen. I figured it's the HD not spinning up fast enough to be detected by the 1200
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Old 10 January 2005, 21:44   #5
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Just noticed - pin 1 (red stripe) cable has been cut - wonder if this could be an issue.... This is the short internal IDE cable I'm talking about here.
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Old 10 January 2005, 22:29   #6
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Taking Pin1 out increases the boot time. The miggy might not catch the boot at first boot (when you power it on first time) but from then on everytime you reset the bitchy hard drive wont sut off and on itself again, thus increasing reset boot times tenfold.

Ive got a 3.5"drive in mine.
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Old 11 January 2005, 19:12   #7
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Yes it does take a while to boot from a reset..... Just as you describe. What is the purpose of cutting pin one, and what would happen if I restored it?
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Old 11 January 2005, 22:11   #8
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I have no blimmin clue but taking it out INCREASES this time. if you put it back it probably takes longer.
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Old 12 January 2005, 18:34   #9
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Okay dude, cheers for that - I'm gonna try it this weekend, just to see.....
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Old 12 January 2005, 18:42   #10
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Somehard drives take a while to spin up. If someone kept finding themselves at the "InsertFloppy" KS screen they might want to do this??
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