exxos's Atari, Amiga & retro forum

PhilC wrote: 15 Apr 2026 16:16 @stephen_usher that does look pretty good actually. Shame about the supports though. I'm sure you'll sort it out.

Yeah, just needs to use "tree" supports I think.

stephen_usher wrote: 15 Apr 2026 16:13 Well, the top case print overnight was a bit of a disaster.

I obviously used the "wrong type" of supports which won't come off the print without destroying it.

Secondly, I'd modified a post to allow for the 74LS145 to fit, except I'd modified the one on the opposite side of the case to the chip.

Thirdly, the spool got stuck at ~4:30am so I lost 5 hours before I found out that the print was a bit naff and it made a line on the two parts where it stopped..

Other than that(?!) it looks quite good and the cut outs for the ports and the keyboard are just right.


IMG_5077.jpeg

Looks great, I'm sure you'll get all the minutiae figured out :)

Last night I determined what was causing the red "ghosting" on the display, one of the three 74LS166 chips is bad. Swapping them around between the three sockets for the colour channels moved the issue. If I only used one chip and put it in the green channel with two of the 166s I'd get a green image, with the third chip, no image at all. More ordered from eBay.

The, hopefully, final version of the top case is printing now. Thankfully it didn't have a filament jam over night. It did have one earlier today, meaning that I've lost 45 minutes. Thankfully the plastic starvation only affected a support. The current ETA is now about 3:15pm (after starting the print at about 1:30am).

stephen_usher wrote: 16 Apr 2026 12:53 Last night I determined what was causing the red "ghosting" on the display, one of the three 74LS166 chips is bad. Swapping them around between the three sockets for the colour channels moved the issue. If I only used one chip and put it in the green channel with two of the 166s I'd get a green image, with the third chip, no image at all. More ordered from eBay.

Bad IC's or just not 'working in this system'?

stephen_usher wrote: 16 Apr 2026 12:53 The, hopefully, final version of the top case is printing now. Thankfully it didn't have a filament jam over night. It did have one earlier today, meaning that I've lost 45 minutes. Thankfully the plastic starvation only affected a support. The current ETA is now about 3:15pm (after starting the print at about 1:30am).

Sounds like you have light at the end of the tunnel :)

rubber_jonnie wrote: 16 Apr 2026 13:46

stephen_usher wrote: 16 Apr 2026 12:53 Last night I determined what was causing the red "ghosting" on the display, one of the three 74LS166 chips is bad. Swapping them around between the three sockets for the colour channels moved the issue. If I only used one chip and put it in the green channel with two of the 166s I'd get a green image, with the third chip, no image at all. More ordered from eBay.

Bad IC's or just not 'working in this system'?

Definitely a bad IC. The behaviour changes with temperature. The other 74LS166 chips behave normally and don't have a temperature sensitivity.

stephen_usher wrote: 16 Apr 2026 12:53 The, hopefully, final version of the top case is printing now. Thankfully it didn't have a filament jam over night. It did have one earlier today, meaning that I've lost 45 minutes. Thankfully the plastic starvation only affected a support. The current ETA is now about 3:15pm (after starting the print at about 1:30am).

Sounds like you have light at the end of the tunnel :)

Yeah. :crossed1:

stephen_usher wrote: 16 Apr 2026 13:53
Definitely a bad IC. The behaviour changes with temperature. The other 74LS166 chips behave normally and don't have a temperature sensitivity.

Fair enough, it happens.

The case is finished! Phew!


I've also published it on Thingiverse just in case anyone else wants to print it: https://www.thingiverse.com/thing:7336456

I don't want to do another large 3D printing project such as this again.

Looks great :)

:bravo:

I just realised that the Xgecu T48 could test the 74LS166...


It's dead Jim! :-)