Posted on Leave a comment

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.

Leave a Reply