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Old 29 April 2015, 08:17   #1
grizzlyaddams
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Amiga 520 PAL or NTSC?

Having trouble getting my Amiga 2000 up and running. Found out the keyboard PCB is smashed in and it doesn't function at all. It doesn't seem easy or cheap to get a replacement.

Secondly, I get a great, sharp B&W picture from the mono video out port.

I got my hands on an A520 but it is giving me only B&W on composite and nothing on RF.

The silver label underneath has some German (or similar) writing. Is this a PAL 520? Does it matter? How can I tell for sure? I contacted the seller and he said "it works on any tv. i had no problem."
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Old 29 April 2015, 10:18   #2
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If the A520 is PAL, that would explain the lack of colour in the output. It might be possible to open it up and configure it to NTSC by changing a crystal, but I am not sure.

I guess the seller had a TV that was PAL compatible. Almost all TVs sold in Europe support both PAL and NTSC, but this might not be the case in the US.
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Old 29 April 2015, 17:34   #3
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Where did you buy the A520 from? The NTSC variants are pretty hard to find but PAL ones are common (in Europe).

Also the Amiga model needs to be NTSC variant for it to produce colour output with the NTSC 520 (no, the software switch is not enough).
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Old 29 April 2015, 18:28   #4
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I've recently had an A520 around, which would only output B/W.

Turned out some solder joints had micro-cracks in them - I've refreshed the solder on every single one and et voilą, the colour was back
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Old 29 April 2015, 18:38   #5
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It is definitely an NTSC A2000, it says so on the label on the back. And it is definitely a PAL A520. I got it from a guy in Tennessee, USA, but it has German writing on the back and a 4.43mhz crystal.

I checked all the solder joints and they did look good. I was going to re-do them even still but I'm almost sure it's a PAL unit anyway.

So there is no chance to get color from this PAL A520 on my NTSC A2000 and television, right?

Thanks.
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Old 29 April 2015, 18:58   #6
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No. It probably wouldn't even give a colour image if you had a PAL TV set.

As ajk said it might be possible to modify it to output NTSC, but apart from changing the crystal you'd probably need to change some component values and/or cut traces on the board. Not worth it when (I assume) real NTSC A520's don't cost that much.
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Old 29 April 2015, 19:02   #7
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Yeah I can't find a listing for a specifically NTSC A520. I really just wanted it for testing purposes as I've read the picture is not good at all.

My ultimate goal is either an Indivision ECS (if they were in stock I'd probably buy it right now) or a RGB to SCART cable with an SCART to HDMI converter.

Even though I'm using an NTSC Amiga with NTSC LCD, the RGB/SCART/HDMI solution will not be a problem, right?
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Old 29 April 2015, 19:22   #8
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forget the A520 , they are hideous things that generate poor quality pictures.

cheap option is an RGB to VGA convertor from China GBS8200. the picture is very reasonable on a via monitor.

or Indivision from Amigakit.

or the old school route an Amiga monitor
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Old 29 April 2015, 19:45   #9
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NTSC A520s don't give such a bad picture, but PAL ones do. For example, the internal A1200 NTSC TV modulator is much worse than A520. It's the opposite with PAL units.

Having said that, I wonder if it would be possible to modify the A520 by replacing the 4.43 crystal with a 3.58 crystal. Although I suspect an additional mod would be necessary for the sound carrier.
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Old 29 April 2015, 19:49   #10
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I considered one of the cheap-o chinese RGB to VGA converters but I would have to build the cable/pinouts to hook it up to the CGA inputs on the converter. Not a big deal but I'd prefer a plug and play solution. The Indivision ECS is my top choice.

I would replace the crystal in the A520 in a heartbeat if that would work, for now, but I'm reading that is not the only mod needed and can't find comprehensive mod instructions.

Also, believe it or not I would LOVE to use an Amiga monitor. I am using an SC1224 with my Atari ST, and it looks and displays great. However, the selection on eBay at the moment is spurious at best. Only 1 real option for us yanks and it doesn't look like it's in great shape.

Last edited by grizzlyaddams; 30 April 2015 at 05:04.
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Old 30 April 2015, 05:08   #11
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Does anyone think it's safe to say with certainty that this A520 does me no good? I discussed a refund with the seller and he already refunded my money, and I told him I would send it back if he did, but did not expect him to right away! It was actually kind of cheap.

I wish most that I could be sure the color output on the RGB itself was working.
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Old 30 April 2015, 09:16   #12
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It's very unlikely that the RGB output wouldn't work, but you can check it with any program lets you adjust the palette. For example Deluxe Paint, or even the Workbench preferences program.

Just play with the R, G and B sliders individually and verify that you see a change in the (monochrome) output of the A520. If all of them have a similar effect on the shade of grey, then the individual R, G and B lines are fine. It's just that the colour information gets output incorrectly for NTSC.
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Old 30 April 2015, 13:23   #13
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Quote:
Originally Posted by grizzlyaddams View Post
Does anyone think it's safe to say with certainty that this A520 does me no good? I discussed a refund with the seller and he already refunded my money, and I told him I would send it back if he did, but did not expect him to right away! It was actually kind of cheap.
If you don't want to send it back, I've been looking at the A520 PCB pics at amiga.resource.cx and the MC1377 datasheet.

I think you could modify your PAL A520 to NTSC by doing this:
  • Replace the 4.43MHz crystal with a 3.58MHz crystal one.
  • Connect pin 20 of the MC1377 chip to ground. If you look at the PCB underside, you'll see a trace running from pin 20. Scratch away the solder mask over the end of that and the opposite site, and put a blob of solder to bridge the gap.
  • According to the MC1377 datasheet you should also change a couple of capacitor values in the filter circuit between pins 10 and 13. However you could probably skip that and still get a colour picture. (Assuming the A520 circuit is similar.)
In July last year quarkx mentioned having some NTSC A520s for sale.

And there are details on how to convert a (PAL) A520 to output S-video at http://members.iinet.net.au/~davem2/overclock/A520.html
The author of that mentions trying the first two steps above to convert a PAL A520 to NTSC and that it didn't work for him...
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Old 30 April 2015, 19:51   #14
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Thanks that is great info. I may even just want to keep it for prosperity and because it was kind of cheap but I hate to waffle with the seller like that.
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