View Full Version : Closed Sinclair Spectrum +2a PSU

12th June 2012, 11:53
Wanted - Sinclair Spectrum +2a PSU

The 6 pin din connector one.

Anyone got one spare.


16th June 2012, 14:48
PM on the way to Jebi1717.


17th June 2012, 14:09
Still looking.... :(

17th June 2012, 14:56

Before we continue we must ensure of which +2 you have

The +2 (GREY)

This uses a 9volt Direct Current (VDC) plug-pack, you can exchange this for anything that provides 9 - 12 volts and upto 1.8 amps of power.

The +2 (BLACK)

Now this is the +2A and +2B, the difference is where they were manufactured, nothing more. very early (and rare) +2A's were in fact a +3 motherboard without the FDD Circuitry / logic installed.

This requires a little more advanced Power Supply - one that can provides +5 +12 and -12 (and of course ground). For my uses here I use a PC ATX power supply -

Here is my wiring schema -
http://s6.postimage.org/laaru6asx/2_AB_3_POWER.png (http://postimage.org/)

its easy to do, all you then need to add is a ON/OFF switch to the PS_GOOD and Ground =)

Alternatively you could use an old A500 power supply - cut the 5 pin plug off (leave a little lead as these are useful) and then add a 6pin DIN in its place with the above wiring - job done =)

24th June 2012, 16:37
Thanks Zetr0

As you are the expert. Does it matter is there is a -12v feed...

Can you plug +5 & +12 and gnd to din PSU socket.

Can the older +2a/b without the extra circuits be made to work with FDD or is your HDD mod the only way insead of using casettes. ?


24th June 2012, 18:42

Sadly my friend, while the -12v is mainly needed for the serial ouput, however its also used to open other gates in the system =D

24th June 2012, 19:08
Thanks for that.

Can the 2a/b board be adapted to run a floppy drive ?

And can they work with your board. ?

Let me know when you are producing more ?

24th June 2012, 19:44

Sadly, for the most part the +2A/B cannot be modified / upgraded to work with a Floppy Disk Drive. However, there are some VERY RARE +2A's with a +3 motherboard with the FDD circuitry removed - it is possible to replace the circuitry and it will work - if you can find the Zilog FDD controller.

Although saying this, these butchered +3 motherboards are extremely uncommon, I know of only 1 person whom has them - these particular motherboards were mostly released in Spain, so finding them on this side of the water is doubly rare, but my friend, you have the luck of the Irish on your side ;)


The Z80 IDE is compatible with all ranges of Spectrum, depending on what version you of Spectrum you have determines the complexity of getting it to work.

The Spectrum +2A/B and +3 are very simple and only need ROM change, where as the earlier 48k/48k+ require desoldering of the CPU and ROM (and some 128k Toast Racks)... the 128k +2 is perhaps the second easiest, with subtle modification to the CF-IDE adapter and ROM.

I hope to be doing another production of these boards soon, but with some subtle differences - but first I will be updating and writing windows software for people to add data to and from their 8bit IDE devices easily.

25th June 2012, 15:27
Thanks for that. Will keep an eye out for the adapter....

Cheers Slainte. :D

26th June 2012, 16:03

Do you know how to change RF Modulator +2ab and +3 to composite


26th June 2012, 16:26

I would suggest that you can get composite output from the 8 pin Din

http://s6.postimage.org/3r1oi9agh/Spectrum_2_AB_3_AV_Pinout.png (http://postimage.org/)

Just use Pins 4 (Composite Sync) and pin 2 (Ground), as the +2AB and +3 introduce a mixed audio / composite input for the UHF modulator - or you will need to seriously modify your motherboard.

Alternatively you can also hook up a SCART socket to it as well, you will need 330Ohm on each of the R,G and B sources -you can tie the +12 to pin 16 and Composite Sync to pin 20 on the SCART connector.

Just to Note
The +12v out on the +2AB and +3 has a 1KOhm inline resistor that drops the output voltage to 0.84 volts when connected to a TV set. The SCART specs require 1 to 3 volts to for the set to select RGB input source - Most TV's work okay with this lower voltage - some (very few) wont.

In regards to the Sound output, the AV socket is a Mono Output and to obtain stereo you would require to modify the motherboard a little bit. However I would suggest getting from this source as there are some flaws in the +2AB and +3 that introduce some really bad sound via RF

26th June 2012, 22:28
So for simple comp output.

Pins 4 (comp Video) & 2 (Gnd) to Yellow comp

Pin 3 (comp Audio) & 2 (Gnd) to Red Audio Comp

Is that right.

26th June 2012, 22:47
indeed =)

21st July 2012, 15:23
Ok using generic charger from External HDD, it only has +12 and +5 but is working perfectly.

Can a moderator please close this thread. :thumbsup:

24th July 2012, 11:47
I'd advice to avoid letting out the -12VDC. As Zetr0 wrote, it is necessary for a correct functionality of your Sinclair.


24th July 2012, 12:23
Thanks for that,

Would it make a difference if I run it from the floppy power head.

I only have one charger and can use this on +2 instead of +3

24th July 2012, 13:52

The -12 is primarily used by the serial port.

25th August 2012, 10:16
closing now on request of op