Power Supply switching between ZX81 & Speccy

Discussions about Sinclair ZX80 and ZX81 Hardware
User avatar
RetroMike
Posts: 47
Joined: Mon Jun 09, 2014 1:33 am

Power Supply switching between ZX81 & Speccy

Post by 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? Image
balford
Posts: 104
Joined: Tue Dec 03, 2013 11:20 pm
Location: Dublin, Ireland

Re: Power Supply switching between ZX81 & Speccy

Post by 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:

Image

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
User avatar
RetroMike
Posts: 47
Joined: Mon Jun 09, 2014 1:33 am

Re: Power Supply switching between ZX81 & Speccy

Post by 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?
User avatar
RetroMike
Posts: 47
Joined: Mon Jun 09, 2014 1:33 am

Re: Power Supply switching between ZX81 & Speccy

Post by 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 :shock: Any clues would be appreciated, but meantime I'm off to Google :)
balford
Posts: 104
Joined: Tue Dec 03, 2013 11:20 pm
Location: Dublin, Ireland

Re: Power Supply switching between ZX81 & Speccy

Post by 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
User avatar
RetroMike
Posts: 47
Joined: Mon Jun 09, 2014 1:33 am

Re: Power Supply switching between ZX81 & Speccy

Post by RetroMike »

Thanks yet again! Image 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 Image

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? :lol:
User avatar
1024MAK
Posts: 5034
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Power Supply switching between ZX81 & Speccy

Post by 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
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
User avatar
RetroMike
Posts: 47
Joined: Mon Jun 09, 2014 1:33 am

Re: Power Supply switching between ZX81 & Speccy

Post by RetroMike »

Good to know, thanks - I've put a watch on it in case mine has further damage that's not immediately evident :)
User avatar
RetroMike
Posts: 47
Joined: Mon Jun 09, 2014 1:33 am

Re: Power Supply switching between ZX81 & Speccy

Post by RetroMike »

Job done. Immitation is the sincerest form of flattery ;)

Image

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 :ugeek:
balford
Posts: 104
Joined: Tue Dec 03, 2013 11:20 pm
Location: Dublin, Ireland

Re: Power Supply switching between ZX81 & Speccy

Post by balford »

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

B
Post Reply