Power Supply switching between ZX81 & Speccy

[RetroMike]

I've got both, the former was considered "done" until I had a thought about this the other night. If I were to put a Speccy socket in the edge of my Zed's board, I could use one PSU for either machine... right? I read that they were the same power pack, and as I have 4 more sockets rattling around the workshop, it sort-of makes sense based on the possibly eroneous assumption that the supplies are the same, and the sockets will have similarly placed pin-outs.

The other option is to get an adapter from the 3.5mm headphone plug to 2.1mm coax... or make my own short-assed fly-lead?

[balford]

Make your own That way you don't have to modify the power socket such that you can't use an original supply on it anymore. Here's mine:



Also, you can use a Speccy PSU with a ZX81 (and suitable adapter), but not a standard '81 supply with a Speccy. '81 supplies are rated for 700mA, Speccy supplies for 1.4A.

(The PSU that comes with a ZX Printer is rated at 1.2A, which may be usable on a Speccy as the standard current draw from a 48K machine is around 700-750mA, but doesn't leave much head room for peripherals.)

B

[RetroMike]

You mentioned this in my other thread, didn't you? Just couldn't remember... My problem presently is that my Speccy PSU has a dodgy wire, so I'd need to replace that... would this be suitable?

[RetroMike]

Found a 2.1mm socket in my bits drawer (actually a bag of around 20!), so just checking on the type for the Zed, and then I'll get some wire. I also need to get the polarity of the plugs so I don't blow one or other device up Any clues would be appreciated, but meantime I'm off to Google

[balford]

That cable you linked to looks good, well overspecced so plenty of tolerance.

The ZX81 power plug is merely a 3.5" mono audio plug, tip positive. Speccy plug is centre negative, outside positive - make sure you get this right or it can cause serious damage to your Spectrum!

B

[RetroMike]

Thanks yet again! I'd dug out my multi-meter (another device I hardly know my way around), and established that a few minutes ago. Why it didn't occur to me earlier, I do not know

I've soldered a new plug onto the Speccy and that seems to be reliably reading 14.xV, so I think there was only the one break in the line... we shall see when I set it up on the device itself. I'll go order a jack plug from this Buy it Now, erm... now?

[1024MAK]

Well, if you do find the cable unreliable, replacements including the 2.1mm power plug are not hard to find.
Here is one from eBay. Any decent electronics supplier will also be able to supply one for you.

Mark

[RetroMike]

Good to know, thanks - I've put a watch on it in case mine has further damage that's not immediately evident

[RetroMike]

Job done. Immitation is the sincerest form of flattery



Shame I couldn't get a gold plated socket, but as I had 20 of them in stock, it would have been churlish to order another 1-5 just for the gold plating

[balford]

Not to worry, to paraphrase Sir Clive that would have been 'quite overgilding the lily'

B