🇩🇪 Robotron KC 87: Part 2 (Powering on) [TCE

[@KolliRail]

Happy to see the machine working! My KC87 came mostly working. I had to replace the big aluminium can filter cap in the PSU to get rid of a lot of ripple that was visible in the video output. After that I ran into problems loading software from tap (actually from a WAV file played on a PC). After replacing a cap that was prominent in the tape input circuit I got it to work in the end. Mine has the RGB output and the picture quality is perfect and vibrant. But I don't really use the machine that much. Without a pixel graphics mode the software doesn't look that good and the keyboard is awful. Probably the worst keyboard of all of my computers including the ZX81.

[@Brfff]

Thanks for the advice! Yes, an interesting choice of key switch for the keyboard. The Czechoslovak SMEP PP01 uses telephone key switches for its keyboard ... not so keen on those other :)

[@imagitu6409]

nice vid.

[@MrWaalkman]

Congrats! That looks great!

[@Brfff]

Very tempted to give the motherboard a "quick clean" to get rid of the dust, but I have this inner voice yelling, "DON'TDUCKITUP! DON'TDUCKITUP! DON'TDUCKITUP! ...." ... so will leave the motherboard as it is (i.e. working).

[@Brfff]

Now that I know it works, I can look at maybe getting this ... somehow. Frustratingly, it seems to not be open source ... available only via occasional auction? www.ebay.com.au/itm/326322869176

[@CheshireNoir]

Sweet! I'd chuck a "medical" meanwell PSU in where the original PSU went. Get one that does +12, -12 and +5 and derive -5 with a 7905. An RPT60B looks like it'd do the job.

[@Brfff]

I'm a little constrained with space ... the PSU space is 95mm wide, 240mm long ... I think the width is the issue

[@crayzeape2230]

Put a 240V light bulb in series with the supply, that'll stop the fuses from blowing and allow for some fault tracing.

[@nojbik]

I'm leaning towards the idea of fixing the original power supply. I know you can fix it!

[@Brfff]

Appreciate the confidence but I think it'll be a long term project. I've not been able to find any short yet - I'm maybe suspicious of the large transformer. I need to figure out a way to current-limit 240VAC into it after I've replaced the fuse with a bit of wire ... then maybe I can see if there is a part that starts to heat up ... ?

[@andrewdunbar828]

Playing with retro system binary file formats for Ghidra I coincidentally just bumped into the KC 87, and the apparently unrelated KC 85. Do you also have a KC 85?

[@Brfff]

Yep - I've got a KC 85/3 as well ... so there's the Z9001, KC85/1, KC87 and then there's the separate KC85/2, 85/3, 85/4 kzbin.info/www/bejne/mZmrZo19ic5nj7c

[@andrewdunbar828]

@@Brfff I've probably watched them all but not all of the makes and models sunk in.

[@Brfff]

@@andrewdunbar828 Yeah, the numbering is a little strange ... I did a graphic in the first KC87 video (28s mark) breaking down the two separate lines of computer: kzbin.info/www/bejne/mqfTYXt8p8x3i5osi=GEl2Xooz0UIaW_8Z&t=28

[@Raul_Gajadhar]

Work next on your breathing, it's a computer video not a weight lifting one, with headphones it's quite disturbing.

[@Brfff]

Noted!