Amiga hardware info, help and support with a focus (but not limited to) North American NTSC experiences. Open to all.
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JEY08
Bath, MI

by JEY08 posted Sat Dec 08, 2018 8:14 pm

Anyone living in the Lansing, MI area with an Amiga 1000 and A1050 memory board?

A couple of years ago my basement flooded and my Amiga 1000 was underwater for a few days before I realized the basement was filling with water.

I recently decided to see if it could be made to work. It has the piggy back ram hack.

I opened it up and it looks pretty clean. There was rust on the front memory expansion shield but the board looks clean. The guide rail for the head in the floppy drive had some rust but it was in a spot that it appeared the head never reaches. That drive is a beast. I decided not to try to clean the rust because I'd have to disassemble it and I'd never get the heads aligned again.

The first time I powered it up nothing happened. There was an NTSC signal for a raster, but no other activity. After reseating the socketed chips It booted up.

The problem is that it only shows 256K of chip ram and 512K of fast ram. The front memory isn't there.

The card edge for the front ram looks ok as does the connector.

I'm not sure if the problem is with the A1050 ram or if it's on the mother board.

If someone lives in the Lansing Mi area that I could try either testing the A1050 in their A1000 or borrow theirs to test in mine it would help to identify which is at fault.

John
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intric8
Seattle, WA, USA

by intric8 posted Sat Dec 08, 2018 10:26 pm

Welcome, John!

I'd be willing to bet it's the A1050 RAM expansion. Those can occasionally be a little bit janky in their connection to begin with.

It's amazing to me that the machine works at all after being submerged for so long! Simply incredible. And the keyboard, too?
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JEY08
Bath, MI

by JEY08 posted Sun Dec 09, 2018 10:28 am

About half the keys would stick down when pressed. Deoxit has mostly taken care of that problem. I used Deoxit-D and I don't think it left quite enough lubricant. If it gets too annoying I'll try deoxit shield which is more of a lubricant.

For the A1050 I guess for now I'll use an ohm-meter to see if all the pads are really making contact. I've ordered a bunch of D41464C-10 dram chips just in case.
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intric8
Seattle, WA, USA

by intric8 posted Sun Dec 09, 2018 10:53 am

Well, if you keep having issues I have a small stack of those front expansions... but good on you for trying to figure it out one way or the other.
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JEY08
Bath, MI

by JEY08 posted Mon Dec 10, 2018 8:01 pm

Looks like I'll have to rebuild the power supply. The -5V has dropped to -3.6V. I don't think anything other than the rs232 serial port uses it.

However, I now get a kickstart prompt, but it doesn't load the kickstart disk. Hopefully it's not the 8520R2 cia. I'll try re-seating those again and hope for the best. I guess there are still a few of those available.

I just realized that the piggyback ram expansion that I had added isn't the one from Amazing Computing. At least not the original article. The motherboard modification part is the same but mine also has modifications to the daughter board. There are two 74LS series chips added, a bunch of jumpers and the DPALCAS and DAUGCAS pals were replaced with versions from C-Ltd.

Anyone familiar with that mod?
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intric8
Seattle, WA, USA

by intric8 posted Tue Dec 11, 2018 8:32 am

Can you take pictures of what you're describing and post them? I may know one person who might be familiar. If not, I can ask around . But pictures are easier to share.
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JEY08
Bath, MI

by JEY08 posted Tue Dec 11, 2018 8:37 pm

This is the daughterboard of my A1000. I wish I had saved the documentation. After so many years I'm not sure whether an update to the piggyback ram hack or something else. There are two chips added. They are stack on two other chips just to get +5V and Ground. Some of the pals have there pins cut and a number of jumpers. Two sockets were added to replace the two pals I mentioned earlier with Cltd versions.

20181211_211219.jpg


This is the piggyback hack on the motherboard. You'll notice the lead that is supposed to go to pin 3 on U6K DPALCAS on the motherboard instead connects to one of the board to board connectors. It leads to a different PAL on the motherboard. This could have been a mistake or it could be there because of the mods. It will take me some time to work out a schematic for it.

20181211_212619_001.jpg
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intric8
Seattle, WA, USA

by intric8 posted Tue Dec 11, 2018 8:40 pm

Hm.. those images are broken (for me). Is it possible they are private and not public?
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JEY08
Bath, MI

by JEY08 posted Tue Dec 11, 2018 8:42 pm

I think it's the way amigalove handles them. They might be too big. Try right clicking on the image and select open image in new tab.
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JEY08
Bath, MI

by JEY08 posted Tue Dec 11, 2018 8:47 pm

I have the floppy drive working again. The track zero sensor is difficult to clean and I think it may still have some dust in it. I blew it out and now it seems to work. Or I could have just bumped a connection and made it better. Who knows.

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