ZX Spectrum & ZX Spectrum+

ZX SpectrumThe ZX Spectrum was released in 1982 after it’s success of the ZX81. Sinclair released seven versions of this model. The first ZX spectrum was released with only 16K Ram expandable to 48K internally. Later Spectrum released another version with 48K of ram. This made the 16K version very expensive and people started to buy the 48K model. The basic is rather slow, and the editor is very strange to work with. I/O capabilities compared with other machines were very limited, however there was a large collection of additional hardware, mostly from third party manufacturers. Although all this still the machine made a lot of success in Europe, especially in the UK. Sinclair released this machine primary for business and educational, but after a short time it became a gaming machine. As all the others Spectrum the ZX does not have a power or a reset switch and the only way you can switch it off is by pulling the plug. The ZX Spectrum+ is identical to the ZX Spectrum. The only difference is the keyboard upgrade. In fact you could buy a kit to upgrade it to a ZX Spectrum+


ZX Spectrum
£125 ($200)
Boxed: 0001-207240 48K
Zilog Z80 8BIT CPU running at a frequency of 3.5 Mhz.
16 Kbytes Rom, 16/48 Kbytes Ram depending on the Model The 16 K version has 16-Kbits x 4 bits DRAM chips. The 48K version has both 16-Kbit and 32-Kbit DRAM chips respectively.
Small black plastic case with grey rubber keys. Like the ZX81 Sinclair embossed their logo on the top left corner of the computer with the ZX spectrum logo underneath. The keyboard area is black in an aluminum plate. On Rubber keys and aluminum plate are printed the basic commands.
Single video mode that mixes both graphics and text with a resolution of 256 x 192 pixels. Characters are 8 x 8 pixel thus it can display text at a resolution of 32 x 24 in 8 colors, and an extra BRIGHT attribute to increase the brightness of the colors.
Simple Beeper driven directly by the ULA. The ULA produces the sound by simply sending pulses to an internal speaker. The sound does not have any volume setting, and is very low since its driven by a single transistor. One can amplify the sound by connecting an amplifier to the Ear out instead of the Tape Deck
1 x RF output that only transmits the video signal. 2 x 3.5mm Jack plugs for tape recorder with a baud rate of 1200 bps. 1 x Expansion bus edge connector.
Common 9VDC 800mA wattage.
The case measures 233mm x 144mm x 30mm (W x L x H). The weight is approximately 1.5Kg.
Sinclair sold more than 5 million units around the world.

The club currently owns two ZX spectrum. One system is boxed with manuals, leads and in good working condition. The other system is used as parts, since it’s completely dead. We also have the flyer that Sinclair produced for promotion. On the flyer Sinclair is comparing the ZX spectrum with a BBC micro.



3.5mm JackFemale at the Computer

Pin Name Dir Desc
2 GND N/A Ground


Expansion Port

54 Pin Edge Connector

Pin Name Dir Desc
U1 A15 OUT Address 15
U2 A13 OUT Address 13
U3 D7 IN/
Data Bit 7
U4 N/C N/A No Connection
U5 D0 IN/
Data Bit 0
U6 D1 IN/
DataBit 1
U7 D2 IN/
Data Bit 2
U8 D6 IN/
Data Bit 6
U9 D5 IN/
Data Bit 5
U10 D3 IN/
Data Bit 3
U11 D4 IN/
Data Bit 4
U12 /INT IN Interrupt Request
U13 /NMI IN Non Maskable Intr
U14 /HALT IN Request Port
U15 /MREQ IN Memory Request
U16 /IORQ IN IO Request
U17 /RD IN Read
U18 /WR IN Write
U19 -5V OUT -5V DC
U20 /WAIT IN Wait
U21 +12V OUT +12V
U22 -12V OUT -12V
U23 /M1 IN Memory 1
U24 /RFSH IN Refresh
U25 A8 OUT Address 8
U26 A10 OUT Address 10
U27 N/C N/A No Connection
L1 A14 OUT Address 14
L2 A12 OUT Address 12
L3 +5V OUT +5V DC
L4 +9V OUT +9V DC
L5 OV N/A Ground
L6 OV N/A Ground
L7 CK OUT Clock
L8 A0 OUT Address 0
L9 A1 OUT Address 1
L10 A2 OUT Address 2
L11 A3 OUT Address 3
L13 0V N/A Ground
L14 N/C N/A No Connection
L15 N/C N/A No Connection
L16 N/C N/A No Connection
L17 N/C N/A No Connection
L18 /BUSRQ IN Bus Request
L19 /RESET IN Reset
L20 A7 OUT Address 7
L21 A6 OUT Address 6
L22 A5 OUT Address 5
L23 A4 OUT Address 4
L24 /ROMCS IN Rom Channel Select
L25 /BUSACK IN Bus Acknowledge
L26 A9 OUT Address 9
L27 A11 OUT Address 11



3.5mm JackFemale
at the Computer

Pin Name Dir Desc
2 GND N/A Ground



35mm JackFemale at the Computer

Pin Name Dir Desc
1 +9V IN +9C DC
2 GND N/A Ground



Phono Jack
at the Computer

Pin Name Dir Desc
2 GND N/A Ground