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I have also found a nice ZX Spectrum laying around. It needs a power source of course to run but there seems to be none that can be used to power it. Google doesn't seem to help and I would love to be able to use a machine that can be used...

Is there a modern power source that can be used to power up my ZX Spectrum?

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    What do you mean by "modern"? A speccy should run with any 9V adapter...
    – Sklivvz
    Apr 19, 2016 at 20:30
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    That's not necessarily true. Check out this video: youtube.com/watch?v=qTRiS4isYGk
    – Bill D
    Apr 19, 2016 at 20:36
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    Not "any" 9V adapter. 800mA is the minimum. Below that, you may suffer from jerky video or various types of malfunction. 1A is the recomended for a bare bones computer. 1.4A is recomended for a ZX Spectrum with hungry peripherals, such as the Interface 1 or the ZX Printer.
    – mcleod_ideafix
    Apr 21, 2016 at 7:32

4 Answers 4

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World Of Spectrum says:

  • Input: 240V AC, 50Hz
  • Output: 9V DC, 1.4A
  • Centre Polarity: -ve (inner diameter is 2.5mm)
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  • I understand the conditions but with power source?
    – Anthony Pham
    Apr 19, 2016 at 21:08
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    @PythonMaster the adapter had 1 transformer, 1 diode bridge and 1 condenser inside of it. It's the cheapest possible transformer with the characteristics above -- I guess that any would do.
    – Sklivvz
    Apr 19, 2016 at 21:15
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    Any power supply with an output spec of 9V DC, current rating greater than specified ought to work (that is the purpose of the specification). The architecture of the supply is not important to a first approximation.
    – Sean Houlihane
    Apr 21, 2016 at 8:49
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    @SeanHoulihane, although if you're going with a cheap unregulated power supply, you don't want the current rating to be too much greater. The voltage of an unregulated power supply depends on the load, so if you seriously underload it, you'll seriously overvolt whatever's attached.
    – Mark
    May 12, 2016 at 18:43
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I've seen a lot of 9V power supplies available, but the crucial thing is that it needs to be centre negative. Sometimes you see units specifically mentioning the Spectrum on ebay, but a useful tip is that 9V centre negative is often still used to drive audio equipment, for example electric guitar effects. I would probably search for one of those power supplies intended to drive a number of electric guitar effects.

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I use this — though rewired for centre negative — and it works well: AC/DC Adapter - 9VDC 2.2A. Circuit-Test make a 9VDC 1.5A centre negative unit that should work without rewiring. Maybe get a Barrel Jack Power Switch while you're at it, since the Speccy has no power switch.

I'm in Canada, so while these units are 110-240 V AC input, the plugs won't work well in the UK.

Guitar pedals, although 9V centre negative, are often only 0.25-0.5 A, so wouldn't be able to power a ZX Spectrum reliably.

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  • You can get a centre positive AC/DC adapter and then a reverse polarity adapter.
    – chx
    Sep 13, 2019 at 8:31
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Be aware that there may be sellers that claim to be suitable, but do not specify whether it is centre negative or not. I bought one, then checked, based on the advice on this forum about the damage that could be caused.

The seller first said it was the wrong one. Then the next day they said it was the right one.

Still no info on whether it was centre negative or not.

So please check, as I have, to avoid damage.

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    There should be a little diagram on the power supply that tells you whether it is centre negative or centre positive en.wikipedia.org/wiki/Polarity_symbols
    – JeremyP
    Jan 4, 2018 at 9:32
  • Thanks. Yes I saw that on another post and checked it. There is no such symbol, sadly. There are other symbols and the KHOI1917 model number. And "Made in China". There is no way it is going to be plugged into the Spectrum.
    – popeymon
    Jan 4, 2018 at 10:00

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