Dandanator Mini 1.3b works on CPC 464 but causes artifacts and RAM errors on CPC 6128

CPC hardware
1

Hi,

The forum finally started working again :slight_smile: I’ve been waiting for this impatiently.

I have a problem with a CPC Dandanator Mini cartridge, version 1.3b. I built it myself and it works perfectly with my Schneider CPC 464, but unfortunately, on my Schneider CPC 6128 there are visible artifacts (I’ve attached a photo).

In addition, when I run the built-in memory test in the Dandanator, the program reports a memory error (I think it was RAM chips 2 and 6, if I remember correctly).

The Dandanator is connected through an adapter (I’ve also attached a photo), because this computer has a Centronics connector. I should add that my M4 board works perfectly on the Schneider CPC 6128 when connected using the same method. The diagnostic test launched through the M4 board also passes without a single error.

The Schneider CPC 6128 seems to have a problem only with this Dandanator.

The first thing I did was build a second identical Dandanator, but unfortunately, it didn’t make any difference, so I think we can rule out the Dandanator itself.

I also suspected the adapter, but I carefully checked the continuity from the solder joints of the Centronics connector on the Schneider all the way to the other end of the adapter, and everything is continuous.

I noticed that the Centronics connector is directly connected to the CPU, which is socketed, so I removed the CPU, cleaned the socket and put it back in. I also checked the CPU socket solder joints and the solder joints of the Centronics connector itself, but everything looks fine.

To be honest, I’m out of ideas at this point.

Maybe there is something I’m not aware of. Perhaps these Dandanator cartridges are not compatible with the Schneider CPC 6128?

I would be very grateful for any suggestions or help.

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Best regards,
Marcin

2

Hi,

Nobody has replied yet, but I’d like to add some more details about what I’ve managed to determine with the help of ChatGPT XD. I know that doesn’t mean much, but I do think it helped me a bit.

We have more or less ruled out a problem with the Dandanator itself and with the adapter. There seems to be something specific to my Schneider 6128 that causes it not to work properly with the Dandanator.

From my observations, the artifacts get progressively worse after each reset (using the Dandanator), until eventually the image becomes completely unreadable. This suggests that the memory is not being properly cleared after each restart and that the problem gradually gets worse.

The built-in test almost always shows a problem with data lines D1 and D6. Only once did it show D5 alone.

So I need to look for something in the computer that is specifically related to the Dandanator, but not to the M4 board, since the M4 board works perfectly without any problems.

The CPC 6128 has additional RAM compared to the CPC 464 — could this be a possible clue?

Everything works perfectly on the CPC 464.

3

Hi there. I asked my colleague at Hobbyretro—who produces the Dandanator Mini—and he told me the issue is related to your CPC, not the Dandanator itself. There is poor communication between the Dandanator ROM and the CPC ROM; the Centronics or edge connector is experiencing unstable communication.

1 Like
4

Thank you very much for your reply.

I don’t think I would suspect the Centronics adapter, because I checked its continuity while it was connected to the CPC. Besides, I have two of them: I bought one from an online store, and I made the other one myself. Both seem to be working properly.

I suspect that something is wrong on the CPC side, between the CPC ROM and the Centronics connector.

1 Like
5

Hi, Marcin

The Dandanator should work without any problems.

Since you don’t have a Dandanator with a Centronics connector, I would try using a Centronics-to-Edge cable that’s as short as possible and/or shielded.

Good luck!

6

Hi,

Thank you for your reply. I have to admit that it did cross my mind that the adapter itself might be introducing some delays, but I dismissed the idea because it worked perfectly fine with the M4 board.

I think I’ll try building a shorter cable, or perhaps even try connecting it without the cable altogether.

Thank you for the suggestion.

Best regards,
Marcin

7

@XeNoMoRPH @itfiddler

Hello again,

Unfortunately, I don’t have good news. I made a PCB that connects directly to the Centronics connector, completely eliminating the cable (I’ve attached a photo). Unfortunately, there is no change.

I’m getting a little frustrated at this point. It is clear that something is not working correctly between the CPC and the Dandanator’s memory. The problem is most likely on the CPC side, but I’m not really sure what else I could check.

I would be very grateful for any ideas or suggestions you might have.

Best regards,
Marcin

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8

@XeNoMoRPH @itfiddler

I just had an idea… As far as I understand, the Centronics port gets almost the entire processor bus from the CPU, which is socketed. As it happens, I think I have a spare one. I just need to compare the markings on the chip to make sure it’s the right one.

I’ll let you know once I’ve checked which one I have in the CPC and what the spare one is before I swap it, because I don’t want to do anything stupid.