Amiga hardware info, help and support with a focus (but not limited to) North American NTSC experiences. Open to all.
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DangerManfred
Hamburg, Germany

Dug out my good ol'e Amiga 500

by DangerManfred Sat Aug 11, 2018 12:21 pm

So my parents found our old Amiga 500 in the attic, in the original packaging even.
I'm pretty sure it still works, but my IT guy senses rang, and before attempting to power it on, I took a look at the expansion slot in the side (empty) and the trap door, which contained an expansion card with what I believe to be 4*128 kB of RAM and 4 more slots for additional RAM chips, as well as a battery (for an RTC?) which was corroded af.
https://imgur.com/uRTPoG4
https://imgur.com/fWlKZ7B
https://imgur.com/4wZ7Cru

So, I have several questions.
1. Does anyone recognize that expansion card? I didn't find a model name printed on it.
2. The battery is probably dead, can I just replace it? And what is the best way to clean the rest of the PCB from the acid or whatever came out?
3. Do the empty slots mean that if I find RAM chips identical to the ones already installed, can I just pop 'em on and enjoy 1MB instead of 512KB additional RAM?
4. If I had modules of a bigger capacity, could I replace the installed ones with them to have, say, 4 or even 8 Megs of RAM?

I'm somewhat on a tight budget, so I wouldn't want to invest a hundred bucks at a time to power up the Amiga, so no insane new power up card for me. But if you know about any cheaper powerups, I would appreciate being told about them.

Anyway, I already got my Retr0bright ingredients and am looking forward to cleaning the machine and finally playing some Might and Magic III and Pac Mania.
Year of Assembly 1989. Got addicted to his family's A500 in the nineties. Recently saved it from being thrown away. Still in love with Might and Magic III, Pinball Fantasies and Pac Mania.
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Zippy Zapp
CA, USA

Re: Dug out my good ol'e Amiga 500

by Zippy Zapp Sat Aug 11, 2018 3:07 pm

DangerManfred wrote:So, I have several questions.
1. Does anyone recognize that expansion card? I didn't find a model name printed on it.

The pictures didnt come through. Try using the attachment feature at the bottom of the editing field.

2. The battery is probably dead, can I just replace it? And what is the best way to clean the rest of the PCB from the acid or whatever came out?

I can't see what kind it is but yes you can usually just replace it with exact or a substitute that won't leak.
The method I us is white vinegar to soak the area and cotton swabs to clean up the corrosion. After you have gotten rid of the corrosion use Isopropyl alcohol to clean the PCB.
3. Do the empty slots mean that if I find RAM chips identical to the ones already installed, can I just pop 'em on and enjoy 1MB instead of 512KB additional RAM?
4. If I had modules of a bigger capacity, could I replace the installed ones with them to have, say, 4 or even 8 Megs of RAM?

Most likely, but again we would need to see the board and what types of RAM chips it uses. If they are DIP they are probably 44256 (256x4 DRAM) but they could also be ZIP chips or something different.
User avatar
DangerManfred
Hamburg, Germany

Re: Dug out my good ol'e Amiga 500

by DangerManfred Sat Aug 11, 2018 9:50 pm

Strange, the images were being shown in the preview, and are still visible on my imgur account.
Anyway, thank you already for the vinegar tip. I'm definitely going to try that.

One more thing I am wondering about: the flip switch at JP1.
From what I googled on the two kinds of chips (i searched for what was written on them), it sits close to an RTC chip and the Mitsubishis are DRAM.
But why would I ever want do disable a clock or the RAM expansion? I remember how in DOS times you sometimes wanted to underclock your CPU, so games whose timing was tied to cycles rather than the actual time didn't have weird speedups on better machines.
But RAM or clock?
This is getting more interesting by the minute.

The info I found on the chips:
clock https://www.amigawiki.org/doku.php?id=de:parts:m6242b
RAM https://www.datasheets360.com/part/deta ... 944036792/
Attachments
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Year of Assembly 1989. Got addicted to his family's A500 in the nineties. Recently saved it from being thrown away. Still in love with Might and Magic III, Pinball Fantasies and Pac Mania.
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ArtstateDigital
United Kingdom

Re: Dug out my good ol'e Amiga 500

by ArtstateDigital Sun Aug 12, 2018 7:32 am

That's a decent looking memory expansion, the fact that there are empty slots for additional RAM was very forward thinking. I hope the clean-up works out for you.
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DangerManfred
Hamburg, Germany

Re: Dug out my good ol'e Amiga 500

by DangerManfred Sun Aug 12, 2018 9:50 am

ArtstateDigital wrote:That's a decent looking memory expansion, the fact that there are empty slots for additional RAM was very forward thinking. I hope the clean-up works out for you.


Yeah, it's one thing I really love about the Amiga - so many things are socketed instead of soldered, so repairs and upgrades are cheap and easy.
In the recent years, "Green IT" has finally become a thing, but the idea of reducing waste by making boards actually repairable without professional equipment has yet to spread to PC hardware developers...
Year of Assembly 1989. Got addicted to his family's A500 in the nineties. Recently saved it from being thrown away. Still in love with Might and Magic III, Pinball Fantasies and Pac Mania.
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McTrinsic

Re: Dug out my good ol'e Amiga 500

by McTrinsic Sun Aug 12, 2018 12:13 pm

That corrosion looks really bad.
The traces might have actually been affected. Just washing probably won't help. Please make sure that whoever takes care of this expansion really knows what to do.

Where do the wires go?

Good luck!
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DangerManfred
Hamburg, Germany

Re: Dug out my good ol'e Amiga 500

by DangerManfred Sun Aug 12, 2018 12:28 pm

McTrinsic wrote:That corrosion looks really bad.
The traces might have actually been affected. Just washing probably won't help. Please make sure that whoever takes care of this expansion really knows what to do.


Hm, that might be a problem. I will first clean it (but won't get to that before Saturday, because I won't get home until then), then look at the traces carefully. I don't know anyone specific who "really knows what to do", but I'm living in one of the biggest cities in my country, so I will probably find someone at a local hackspace or something like that.

McTrinsic wrote:Where do the wires go?!


They go to a flip switch.
Year of Assembly 1989. Got addicted to his family's A500 in the nineties. Recently saved it from being thrown away. Still in love with Might and Magic III, Pinball Fantasies and Pac Mania.
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Zippy Zapp
CA, USA

Re: Dug out my good ol'e Amiga 500

by Zippy Zapp Sun Aug 12, 2018 2:21 pm

Yeah that looks like it will take some extensive repair. After you remove the battery you may have to desolder the sockets the RAM was in and the main connector. It probably wouldn't hurt to soak the whole board in vinegar. One board I had like this I soaked it in Baking Soda mixed with water.

You will have to also check the A500 expansion connector that this plugs onto as the green corrosion probably went on to the pins of the A500 too. As pointed out you may have to repair some of the traces.

As for the switch, it probably disables the board. There were a few very early games that didn't work with any sort of expansion RAM enabled, for whatever reason.
User avatar
DangerManfred
Hamburg, Germany

Re: Dug out my good ol'e Amiga 500

by DangerManfred Tue Aug 14, 2018 3:42 am

I highly doubt I should start with my Amiga when soldering for the first time ever.
But then again, I don't see any other chance to get my RAM expansion working again.
I don't know about the Americas, but here in Europe, every expansion card with >1MB capacity or turbo cards in general is always in the triple digit price range, which is kind of ridiculous when the Amiga itself goes around 50 bucks.
Year of Assembly 1989. Got addicted to his family's A500 in the nineties. Recently saved it from being thrown away. Still in love with Might and Magic III, Pinball Fantasies and Pac Mania.
User avatar
femuruy

Re: Dug out my good ol'e Amiga 500

by femuruy Tue Aug 14, 2018 5:48 am

You can get a very decent new 2mb trapdoor expansion like this http://www.boobip.com/hardware/A500_2MB (just bought one a few weeks ago) for a very reasonable ammount, personally i would try to stabilize the old expansion (Battery removal, acid wash + isopropanol rinse) and put it on storage ...
Best,
FemurUY
Looking forward to get any of the AGA Amigas!

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