RF Video Distortion

[1024MAK]

Quite a significant difference, isn't it? I'm sure my Speccy was knocking out about 14v, but as the wire is froobed, it was transient to say the very least

The Sinclair "9 volt" power supply units are unregulated. What does this mean? It means the output voltage is NOT constant. When not connected to a computer, but plugged in to the mains supply, the output voltage will be between 12V to 15V.

Incidentally, where does the power that used to be turned to heat go on the new one

These "switching" regulators are actually very small switch mode power supply units. These chop the input dc into high frequency pulses, then smooth out the pulses to get a dc output. Because the transistor inside it is switching between fully on and fully off, very little power is lost, so very little heat needs to be dissipated.

This is a totally different system to that used in a 7805 regulator.

Mark

[RetroMike]

Nice! In't technology wonderful when it works? Incidentally, I'm now able to post on WOS so I hope they're feeling tolerant over there

[balford]

I'm sure they don't bite (insert Suarez joke here)

B

[RetroMike]

Turns out they don't now I'm validated, and one of them has shown a tendency toward alcohol consumption and humour. Not much more I can ask, is there?

On a ZX related note, I'm now working on integrating the ZXpand into the Memopak16k case, and as mentioned in the instruction sheet, it's a perfect fit, with the PCB slotting straight into the rail that runs the length of the box. I've just Dremelled out the slot for the SD card in the end cap, which I thought were plastic, but turned out to be aluminium. Good job I have a mains powered Dremel as well as my battery powered one... the drill press attachment came in very handy for the chain drilling of the basic slot too.

I need to ask Charlie about the LEDs, and what I should solder in place to have them showing through the case. Either that, or I could experiment with a short length of acrylic rod inserted through the chassis to act as a sort-of fibre-optic link

[Moggy]

If you look at my pic of one of my setups on page one of this thread you will see my solution was to drill two small holes in the Memotech case and use the insulator from and old modulator as a diffuser for the LEDS also it coincidently is the right spacing. I did have to put a very tiny piece of blutac in-between the LEDS to separate them optically and stop the different colours appearing in each side of the diffuser, and whilst not everybody has a spare insulator hanging around any piece of suitably opaque plastic should suffice as the LEDS are plenty bright enough. Also remember to pack each end of the case as needed with blutac to line up the holes with the LEDS as the ZXpand can slide left to right in the case by a cm or so if unpacked.

One final point , should you decide to get the AY device for the Xpand then it will no longer fit in the Memotech case.

[RetroMike]

Thanks for that I was actually thinking of wiring them into the end cap rather than trying to get them lined up with any holes I drilled. You know how easily that could go wrong

I've always wondered why I'd want an AY board on a ZX81, as I don't remember any games with sounds on it. Am I wrong again (as usual)?

[sirmorris]

I was going to suggest speaking to Moggy about the LED issue I would do what he did. It saves some potentially worrying surgery on the board. I actually provided solder pads on the issue one board, but (ahem) never actually tested them - and they didn't work properly (well, as intended) so I dropped them for issue 3

Go with drilling a couple of holes in about the right place. Thinking about diffusion I also had a notion about using hot glue, which dries (cools?) translucent, and is very easy to work both when it's hot and cold. Another benefit is that if it fuffs up, then you only have to wait 10 seconds before you rip it out (cleanly!) and have another go

I've collected many light tubes and pipes in my time but nothing has ever been quite right. Separating the leds with a barrier is a good idea, or you could use one bigger hole to see both! They're never lit at the same time so it doesn't matter Plus alignment isn't so much of an issue then. Speaking of which - when I had my board cased I used sticky foam pads on the end pieces which kept the board nicely central.

I can post a 1:1 PDF of the board if that would help with alignment?

[sirmorris]

re: the AY/games thing - yes you're 99.99% right. The only game I know with AY sound was QS Defender, and that's using QS' own mapping, which is not compatible with Zon/Mrx/ZXpand-ay.

There have been some modern productions but I think the zx81+AY is best for experimenters

[balford]

I can vouch for hot glue:


The LEDs on the left are illuminating through hot glue that's flush to the case contours.

B

[Moggy]

Thanks for that I was actually thinking of wiring them into the end cap rather than trying to get them lined up with any holes I drilled. You know how easily that could go wrong

I've always wondered why I'd want an AY board on a ZX81, as I don't remember any games with sounds on it. Am I wrong again (as usual)?

Why just games?

You can while away the hours listening to the many music files produced for the AY.
I have a couple of thousand if You ever decide to bother with it.