What's this trapdoor expansion board?

amiberks · 18 July 2019, 17:48

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...

DofD · 18 July 2019, 18:11

It certainly does look like a memory expansion, there are unpopulated spots there for a battery and for the bits for a clock.

amiberks · 19 July 2019, 01:13

Thanks for looking! I'll report back as soon as I find out

hooverphonique · 19 July 2019, 10:38

I agree that it mostly looks like a memory expansion. Strange numbers on those memory chips though...

nogginthenog · 19 July 2019, 19:10

Definitely RAM chips. Soldering looks a bit dodgy. Wonder if these are re-used from a simm module?

DofD · 19 July 2019, 19:17

Quote:

Originally Posted by nogginthenog

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.

Hewitson · 22 July 2019, 07:28

I wouldn't say it's reworked, I'd say it's a homemade/DIY card.

amiberks · 22 July 2019, 17:12

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

nogginthenog · 22 July 2019, 20:37

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?

amiberks · 24 July 2019, 13:24

Quote:

Originally Posted by nogginthenog

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!!

nogginthenog · 24 July 2019, 20:42

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.

Hewitson · 25 July 2019, 10:01

The A520 produces the worst picture quality of all time. Even the RF from an Atari 2600 would probably be better.

amiberks · 27 July 2019, 22:55

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!

amiberks · 29 July 2019, 09:53

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

Glen M · 29 July 2019, 10:08

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.

amiberks · 29 July 2019, 22:40

Ah! No probs then; it was more the comparison than any issue with the scart :-)

18 July 2019, 17:48	#1
amiberks Registered User Join Date: Jul 2019 Location: Berks Posts: 9	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...

19 July 2019, 10:38	#4
hooverphonique ex. demoscener "Bigmama" Join Date: Jun 2012 Location: Fyn / Denmark Posts: 1,624	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.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Trapdoor ram expansion question	morbius	New to Emulation or Amiga scene	17	16 February 2016 22:53
Another A1200 trapdoor expansion	mikele	MarketPlace	3	09 May 2012 15:14
Trapdoor expansion options for A500	Impakt	support.Hardware	7	20 March 2008 06:05
A500 Plus Trapdoor Expansion	TheCorfiot	support.Hardware	10	14 March 2008 16:42
Removing a trapdoor expansion	numb	New to Emulation or Amiga scene	14	08 March 2005 23:40

18 July 2019, 18:11	#2
DofD Registered User Join Date: Jun 2018 Location: Victoria, Canada Age: 56 Posts: 134	It certainly does look like a memory expansion, there are unpopulated spots there for a battery and for the bits for a clock.

19 July 2019, 01:13	#3
amiberks Registered User Join Date: Jul 2019 Location: Berks Posts: 9	Thanks for looking! I'll report back as soon as I find out

19 July 2019, 19:10	#5
nogginthenog Amigan Join Date: Feb 2012 Location: London Posts: 1,309	Definitely RAM chips. Soldering looks a bit dodgy. Wonder if these are re-used from a simm module?

22 July 2019, 07:28	#7
Hewitson Registered User Join Date: Feb 2007 Location: Melbourne, Australia Age: 41 Posts: 3,772	I wouldn't say it's reworked, I'd say it's a homemade/DIY card.

22 July 2019, 17:12	#8
amiberks Registered User Join Date: Jul 2019 Location: Berks Posts: 9	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

22 July 2019, 20:37	#9
nogginthenog Amigan Join Date: Feb 2012 Location: London Posts: 1,309	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?

24 July 2019, 20:42	#11
nogginthenog Amigan Join Date: Feb 2012 Location: London Posts: 1,309	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.

25 July 2019, 10:01	#12
Hewitson Registered User Join Date: Feb 2007 Location: Melbourne, Australia Age: 41 Posts: 3,772	The A520 produces the worst picture quality of all time. Even the RF from an Atari 2600 would probably be better.

27 July 2019, 22:55	#13
amiberks Registered User Join Date: Jul 2019 Location: Berks Posts: 9	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!

29 July 2019, 09:53	#14
amiberks Registered User Join Date: Jul 2019 Location: Berks Posts: 9	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

29 July 2019, 10:08	#15
Glen M Registered User Join Date: May 2017 Location: Belfast Posts: 750	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.

29 July 2019, 22:40	#16
amiberks Registered User Join Date: Jul 2019 Location: Berks Posts: 9	Ah! No probs then; it was more the comparison than any issue with the scart :-)

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)