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Sinclair ZX Spectrum Power Supplies – What Types Are There (Part 6)? – The First One? UK1200?

When I started doing the research, opening up lots of Spectrum power supplies, and writing this series of articles, I had thought that the UK1400 power supply was the first one for the Spectrum, as shown below.

Power Supply for Rubber Key and Plus Types of Sinclair ZX Spectrum

But I was told by members of the Spectrum community that there was a UK1200. I had never seen one in the flesh… UNTIL NOW!

I have got one NOW! How exciting!

Model name: UK1200

Input: 240V AC

Output: -12.5V DC approx., unloaded (unregulated), maximum current rating 1.2A (1,200mA and hence the name UK1200).

When under load and being used on a Spectrum, the voltage will be nearer to what is stated on the PSU label.

Polarity: Centre Negative (not positive) Outer Positive (not negative as on most barrel connectors).

Getting the polarity is essential if you do not want to damage your Spectrum.

I do not know whether the UK1200 power supplies are suitable for any other model of Spectrum than the Issue1 Spectrum.

The strain relief on the PSU is not as stiff as on the UK1400. This might mean that it lasts longer because they are notorious for breaking.

It has a barrel connector that is not smooth. The UK1400 that was subject to a safety recall had a smooth barrel and black and white DC cable.

The insides are very similar to the UK1400. It is a full wave bridge rectifier with two smoothing capacitors. And a fuse.

I cannot verify that it the UK1200 would work on an Issue 1, because I do not own one.

However, the fact that the UK1400 power supply followed the UK1200 – or even possibly was being sold at the same time as the UK1200 – suggests that 1.2A was insufficient for the Spectrum and 1.4A was needed.

The UK1200 certainly won’t be suitable for the 128 “Toastrack” and not the (Amstrad-era) Spectrum +2 Grey. This is despite the fact that the DC (computer side) barrel connector will fit on these later models of Spectrum.

I would not recommend running any Spectrum with the UK1200 and without an Issue 1, I have no intention to!

And sorry. This power supply is not for sale.

But I do have a range of other power supplies for sale. The series of articles on this website is there to help you choose the right one.

Before use all power supplies need to be checked for safety, as well as functionality and that they are delivering the right voltage levels, current and polarity. So please note that they must be checked before use, and check the Safety article.

If you are looking to buy any power supply or want one checked, please get in touch. I will happily sell you one – fully tested and working – for the Spectrum 16/48k/Plus, for the grey +2 or the black +2 or +3. I also have a lot of other Spectrum parts, working computers and games for sale. I will happily put together a custom bundle for you.

I would like to credit and highly recommend the excellent videos by “JoulesPerCoulomb” on Youtube. “Greetings and good time of day…” to whoever this mysterious but extremely helpful man, is. His video on power supplies was a brilliant starter a few years ago to the many hours of research that I have conducted since on Spectrum power supplies, and which I present in this series of articles.

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A Look Inside the Original Spectrum Power Supply (16/48k Rubber Key Models)

The UK1400 PSU
The UK1400 Power Supply Unit (PSU)

On this PopeyMon Games and Fun website, in a series of articles I have tried to described all types of power supply unit (PSU) for the Sinclair ZX Spectrum models.

This goes from the first 16k and 48k rubber key models when the Spectrum was owned by Sinclair to the final disk drive version of the Spectrum, the +3 under the ownership of Amstrad. There is an index to the articles, as Part 0 of the series.

In this article, I am delving into the inside of the original Spectrum power supply, the UK1400 model.

I say original, but I’ve been told from several credible sources in the Spectrum community that the Issue 1 Spectrum had a UK1200 model. Until I see one being used on an Issue 1 Spectrum “in the flesh”, I will still call the UK1400 the original Spectrum PSU.

The UK1400 was used for all rubber key models of the Spectrum – 16k and 48k. It was also used on the Spectrum Plus with a different design.

This earlier article also talks about the UK1400. But I want to go a bit deeper here. Here are six images of the components inside the UK1400. As in the earlier article, there are several designs of the UK1400.

They are all implementations to the same specification. And all of them use a full-wave bridge rectification circuit to convert the mains 240V into around 12-14V DC (unregulated and when unloaded) via a barrel connector to the Spectrum board.

Note: A “smooth” barrel connector has been used to replace the original on the photo at the top of the article. Please see the Safety Warning article for more on the UK1400 production that were recalled for safety issues.

Each of the designs meet the UK1400 PSU Specification in different ways.

Some designs are compatible with other designs and some are not.

There are different orientations of the PCB and transformer – some designs have the PCB underneath the transformer and other designs have the PCB at right-angles and to the side of the transformer.

There are different versions of the case, so they are not interchangeable with different designs. Here is one case from a PSU that failed its tests.

And as I have said on other articles, BEFORE you plug any power supply into your beloved Spectrum, please CHECK is it safe to use: (i) for you, (ii) for your Spectrum.

I have TESTED and WORKING PSUs for sale in the PopeyMon website shop and in the eBay popeymon shop too.

If you have any questions, please get in touch.

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Sinclair ZX Spectrum Power Supplies – What Types Are There (Part 2)? – The Toastrack

The much sought-after Sinclair ZX Spectrum 128 “Toastrack”

There are several types of Sinclair ZX Spectrum. So it follows that there are several different types of power supplies for the Sinclair ZX Spectrum.

This ranges from the rubber key 16k and 48k models, then Plus and 128 models during the Sinclair ownership of the Spectrum brand, through the Amstrad ownership of the Spectrum brand (after Alan Sugar’s Amstrad bought the rights to the Sinclair Computer brand), to the present with the new Spectrum Next.

Part 1 of the PopeyMon articles on the types of Spectrum PSU talked about the rubber key models and the Spectrum Plus.

This article (Part 2) talks about the only 128k Spectrum of the Sinclair era – the Sinclair ZX Spectrum 128 (a.k.a. “Toastrack”).

The Toastrack computer looks very similar to the Spectrum Plus, but has a huge black heat sink on the right-hand-side of the case. Hence the name, the “Toastie” or “Toastrack”. Inside, it is quite different, as well as the obvious extra RAM.

The left and right hand sides of the Spectrum 128 Toastrack
Power Supply for Rubber Key and Plus Types of Sinclair ZX Spectrum

The power supply (PSU) shown in the photo above is a UK1400 model, which is OK for use on 16k and 48k rubber key models. The one below is the Spectrum Plus version of the UK1400.

Like the computer itself, there is a similar look of the Plus PSU and Toastrack PSU.

Spectrum Plus version of the UK1400 Power Supply

None of the UK1400 power supplies are suitable for any other model of Spectrum – not the 128 “Toastrack” and not the (Amstrad-era) Spectrum +2 Grey.

This is despite the fact that the DC (computer side) barrel connector will fit on these later models of Spectrum. And despite the fact that the Spectrum Plus UK1400 looks very similar to the Toastrack PSU.

Why? Because the power requirements of the Toastrack and Grey (subject of a future article) are higher than the 16/48 and Plus. They require more current than the UK1400 can deliver.

The UK1400 model is called the UK1400 because it delivers a maximum of 1,400 mA (milli-Amps). Or put another way, 1.4A (1.4 Amps).

The Toastrack needs more than 1.4A.

The Toastrack power supply can deliver more current. It can give 1.85A. This is why it is called the UK1850. Here is a photo:

Spectrum 128 “Toastrack” Power Supply

You can see in the photo above that the case has the textured right-hand-side, which is different to the Spectrum Plus UK1400 PSU.

Underside of the Toastrack PSU

On the underside of the PSU, you can see in the photo above that the model number is UK1850 and the maximum current is 1.85A. The quality of work inside seems to be higher than in some of the UK1400 models.

The official Toastrack power supply is becoming hard to find now, especially in a decent condition. This is the only one that I have, at the time of writing. So I have not been able to do a comparison of the internals, like I did in Part 1 with the UK1400 model.

This Toastrack PSU needs some work to clean it up and to replace the mains cable, but it has been tested including an electrical safety (PAT) test and it is working. The PAT test failed due to a nick in the mains cable insulation, so it would not be for sale in the PopeyMon eBay shop until that was fixed. But it’s the only I have, at the time of writing!

If you are looking to buy any Sinclair power supply or want one checked, please get in touch.

I will happily sell you one – fully tested and working – for the Spectrum 16/48k/Plus, for the grey +2 or the black +2 or +3. I also have a lot of other Spectrum parts, working computers and games for sale. I will happily put together a custom bundle for you.

I will be writing more about more Spectrum power supplies in the near future. Watch this space! Part 3 is now here.