question about modification in Amstrad CPC464

[sokot]

Hey,

I recently bought an Amstrad CPC 464 in good visual condition with one modification that I know nothing about. So I have a question. Can you tell me what this modification might do? Visually, nothing changes when I flip the switch, except that games (I tested with Bruce Lee) from the DDI5 cartridge either don't load or load depending on the position of the switch. I'm attaching a few photos so you can see what the modification looks like. There are two white cables running from the switch to the board, and the photos show where they end up. There is also a red cable connecting two places on the motherboard.

 https://drive.google.com/file/d/1yLEYDgC8mwd3HUr032PREJEKtgO97pBI/view?usp=sharing

https://drive.google.com/file/d/1KW3SjBpEmDDBhEptMm6LlqXQYDb1RaJK/view?usp=sharing

https://drive.google.com/file/d/1fWKLmWJbKD0NGwlJ9oyuHkLkpsq-e3TN/view?usp=sharing

https://drive.google.com/file/d/1TD7CCCn70vNJ1IHNX-TSs2wn67wymvpd/view?usp=sharing

https://drive.google.com/file/d/15kJ-wxgQm4q5mHR74M4e5TuCD8Ws9r4F/view?usp=sharing

https://drive.google.com/file/d/1fum1kmRiUrFLmeij-69cseh6ThAzhMSi/view?usp=sharing
 
The second issue is that the upper RAM memory on bank 8 crashes during the diagnostic test, but everything goes smoothly during the second memory test. Overall, the computer does not seem to have a memory problem, but I am not sure what to think about it. Maybe it is related to this modification? I am also attaching the test results. I would appreciate any advice.

https://drive.google.com/file/d/11HtWRwG8Wgdxb0oHNJ1dKKFKBZK0duDR/view?usp=sharing

https://drive.google.com/file/d/1wIrar6dbqyzY6AQVshAJyf193AmIDbAr/view?usp=sharing

[pelrun]

The red wire is an 8-bit printer port mod.

If the switch is connected to LK4, that's a refresh-rate selector. That's a weird mod on the CPC, since there's nothing that uses 60Hz, unlike other platforms that have PAL/NTSC variants. https://www.cpcwiki.eu/index.php/LK_Links

[sokot]

Thank you for your reply. What do you think about the upper memory error? Do you think it's something to worry about if another test doesn't show a problem?

[Bryce]

Hi sokot,
       you haven't posted any pictures of the RAM expansion. Can you take a few pictures of it, so that we know what type of expansion it is and how it's connected?

Bryce.

[sokot]

The extension comes with this cartridge, and the diagnostic program is also run on it as dsk.

 First looks at the DDI5 for Amstrad CPC 464 | Amstrad noob

[Bryce]

The extension comes with this cartridge, and the diagnostic program is also run on it as dsk.

 First looks at the DDI5 for Amstrad CPC 464 | Amstrad noob

Ok, then you probably just have a dodgy (intermittent) connection on the expansion port. Clean the expansion port contacts on both sides of the Mainboard PCB and the problem will most likely be solved.

Bryce.

[sokot]

Thank you very much for your suggestion. I will do that