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Old 18 July 2019, 17:48   #1
amiberks
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What's this trapdoor expansion board?

Found it inside the A500 I just bought. I am still waiting for some cables and adapters to be able to connect it to a monitor, so I can't boot up with and without the card to see the difference

https://imgur.com/a/UISuXdt

All the chips are branded IBM...

There are two 89x8922 (first and last), a 23f8187 and a 6161764... It really seems to be a memory expansion, but I have no idea...
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Old 18 July 2019, 18:11   #2
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It certainly does look like a memory expansion, there are unpopulated spots there for a battery and for the bits for a clock.
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Old 19 July 2019, 01:13   #3
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Thanks for looking! I'll report back as soon as I find out
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Old 19 July 2019, 10:38   #4
hooverphonique
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I agree that it mostly looks like a memory expansion. Strange numbers on those memory chips though...

Last edited by hooverphonique; 19 July 2019 at 23:32.
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Old 19 July 2019, 19:10   #5
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Definitely RAM chips. Soldering looks a bit dodgy. Wonder if these are re-used from a simm module?
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Old 19 July 2019, 19:17   #6
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Quote:
Originally Posted by nogginthenog View Post
Definitely RAM chips. Soldering looks a bit dodgy. Wonder if these are re-used from a simm module?
Looking at the picture again, yeah, the soldering does not look good and the card certainly does look like it's been reworked.
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Old 22 July 2019, 07:28   #7
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I wouldn't say it's reworked, I'd say it's a homemade/DIY card.
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Old 22 July 2019, 17:12   #8
amiberks
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I also noticed some weird soldering (i.e. it didn't look like the usual soldering from non-DIY stuff), however as I'm not an expert I wasn't sure!

I haven't got the necessary video cables yet, so the most I've been able to do is boot it up without a screen. It seems to try to read from disk every few seconds. If I insert a random disk (non-Amiga as I have none) it seems to try to read it for a couple of seconds and then just stops. The behaviour is the same with and without the card.

Doesn't sounds too bad to me, but then again I'm a complete newbie on Amigas
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Old 22 July 2019, 20:37   #9
nogginthenog
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Sounds good.

Nothing on there will leak (your clock will be wrong though).
I think the RAM chips have been recycled from a SIMM module.

The A500 has Black & White composite output on the far left if that helps. I guess you ordered a SCART cable?
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Old 24 July 2019, 13:24   #10
amiberks
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Quote:
Originally Posted by nogginthenog View Post
The A500 has Black & White composite output on the far left if that helps. I guess you ordered a SCART cable?
It came with the A520, so I tried to use that with a composite->scart and scart->hdmi contraption (which works for other devices), however I don’t have confidence this or the lcd I’m using are appropriate for this task as I don’t get any output. I have now ordered the SCART cable and I’m waiting for delivery.

I’ll try the B&W composite output this evening, not sure why I didn’t try before!!
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Old 24 July 2019, 20:42   #11
nogginthenog
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The A520 is garbage. I can't believe I squinted at the blurry output for years when all my TVs supported SCART. Had a nice Sony Trinitron TV too.


I upgraded to a Philips CM8833 and later to a VGA monitor when I got a graphics card.
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Old 25 July 2019, 10:01   #12
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The A520 produces the worst picture quality of all time. Even the RF from an Atari 2600 would probably be better.
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Old 27 July 2019, 22:55   #13
amiberks
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So I ordered a SCART cable but I still have to convert the signal to HDMI. I have a weird 13" small monitor for these things (my main monitor is USB C only) and I can't seem to make it work. I'm looking into it, but in the meanwhile I did however confirm the Amiga works with the monochrome output, thanks for the tip!
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Old 29 July 2019, 09:53   #14
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Dug up an old-ish 42" LCD with scart input and the scart cable works. The image doesn't seem to be amazing if I compare it to what I see in some Youtube videos, e.g. [ Show youtube player ] but at least I know the computer works like a charm
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Old 29 July 2019, 10:08   #15
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What you see on the youtube video is run in WinUAE at a high resolution (wrong aspect ratio I would add) and by the looks of that video there is also a filter applied to it.

Amiga over RGB-Scart is about as good as you can get on the real thing.
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Old 29 July 2019, 22:40   #16
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Ah! No probs then; it was more the comparison than any issue with the scart :-)
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