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The MKII trace looks like what I would expect. The ISS2 trace looks like something weird is going on like the scope connections are reversed, or is not connected to the LS86 output. Ignoring the inversion and distortion the two waveforms are the same.

Can't recommend a good wall wart I'm afraid Just a random thought: I've not measured so can't say for sure, but a laptop PSU must be built to a far higher standard than a typical wall wart. At least I've never felt like I'm being electrocuted when using a laptop. If you can find an old 12V laptop s...

The culprit is probably common mode noise which can be surprisingly hard to get rid of. This will be bouncing relative to the mains (and therefore ground) at the PSU end and turned into a signal at the monitor end. Ideally you would attempt to block with a decent common mode choke close to the PSU a...

Hi, Unfortunately this is a normal 'feature' of a Dragon. It's just dot crawl resulting from a lack of fixed relationship between the pixel and chroma clocks. Later versions have a 2-22pF trimmer cap in the position of C7. This can be adjusted for best appearance but it will drift due to temperature...

Hard to make out the details on my copy of the ISS2 schematic but it looks like that pin is the 'padded for PAL' /hsync, in which case the MKII equivalent is IC14 pin 6.

Heh, that's a fun listen

I particularly like "For Whom the Code Runs", "In the Cooler" and "Nuclear Green"

Excellent work as usual Ciaran

robcfg wrote: ↑Fri Mar 15, 2024 7:16 pm Tell me more about that mini keyboard of yours

Just a little something for the lulz. Details here: https://gitlab.com/sorchard001/mini-dragon-keyboard

Not sure if you were specifically interested in the Dragon version but there is a lot of PL9 stuff here:

https://www.simonwynn.com/flex

(In fact a *LOT* of Flex images in general)

Looking good Rob! I think the two DRAM types are nearly equivalent, or at least I'm sure I've had both types in my Dragons. I found this handy reference the other day. Might be of use: https://minuszerodegrees.net/memory/4164.htm Those 3 connectors look like DIN41612 type B 64 way to me, probably so...

Ah, so this is where all the fun is happening! That's awesome :) I could be wrong but I think the majority of 256K drams had 8 bit refresh. After that the industry moved to CBR refresh and you didn't need a refresh counter any more. I'm curious to know if the logic to recreate the glitching is using...