24-pin ROM replacement module

• Replaces 24-pin 8KB (and 4KB*) ROMs that have the standard EPROM pin out (eg: TMS 4764) and an active low output select pin, such as the breadbin C64's Kernal, BASIC and Character ROMs and Sinclair Interface 1 ROM
• Has an onboad switch allowing two different ROM images to be selected, if desired.
• Uses a very low power modern EEPROM chip.
• Please email me the ROM images you require on the module after purchase.
• Note: The module cannot be reprogrammed in a standard EPROM burner as it requires a special interface to set up.
• Currently PCB color: Black.

* Regarding 4K ROMs: As long as pin 21 on the PCB that's using a 4K ROM is tied high or low (ie: not left floating) no PCB modification is required (if it is floating, just connect pin 21 to pin 24 or pin 12 - either is fine). (In the breadbin C64, the Character ROM (U5) is 4KB, and pin 21 is pulled low already on the PCB so modification is required. (The BASIC (U3) and KERNAL (U4) ROMs are 8KB.)

4116 Spectrum "Lower RAM" Chip

• 4116 RAM (150ns) chips used for Lower RAM in ZX Spectrum (and in other machines such as the TI-99/4A)
• Good condition, never soldered and tested for 2 hours before dispatch in a Spectrum running memory test.

The 48K and 16K Spectrum uses eight 4116 chips for the lower 16KB of RAM. A chip can fail quite readily (especially following edge-connector related mishaps) - usually causing the Spectrum to not initialize on power up (often with the classic dead-Spectrum vertical black+white columns / flashing attribute blocks display).

Sometimes a bad chip can be detected simply by its temperature - if it is noticeably warmer than those around it, it will be highly suspect. Another crude but often effective test is to "piggy-back" a working chip on each RAM chip one at a time. If the error goes away or at least changes, there's a good chance that chip is faulty.

4164 Spectrum "Upper RAM" Chip

• Organization: 64K x 1, Speed: 150ns or faster, 128-cycle refresh, Package: 16 pin DIL
• Unused, old stock parts. Good clean condition and tested for 2 hours before dispatch.
• Can be used individually or in any quantity to replace any of the original Upper RAM chips used in the Spectrum 48K (eg: Texas Instrumenents TMS4532-15NL3, TMS4532-15NL4,  OKI M3732H-20, M3732L-20). Any valid setting of the Spectrum RAM type jumpers is fine when using these chips (please see this page for more info regarding the Spectrum's Upper RAM.)
• These chips cannot be (directly) used to replace the "4116" chips used for the LOWER 16KB of RAM in the bottom left of the Spectrum's PCB.
• Also suitable for the C64, Spectrum 128 and grey 128 +2 (but not the +2A or +3)

74HCT00 Logic IC

• A modern lower power replacement for the 74LS00 logic IC in the ZX Spectrum

74HCT157 IC

• A modern lower power replacement for the 74LS157 logic IC for ZX Spectrum IC25/IC26 (it's probably best to stick with the original 74LS157 types for IC3/4 as the timing there can be critical).

74HCT32 Logic IC

• A modern lower power replacement for the 74LS32 Logic IC in the ZX Spectrum

74LS00 Logic IC

• Replacement logic IC for the ZX Spectrum (Quad NAND gate at IC24)

74LS04 Logic Inverter IC

• As used in Issue 6A Spectrum motherboards and also on some models of Spectrum 128
• When the 74LS04 is faulty, issues such as the Spectrum only seeing 16K occur
• Brand new

74LS157 IC (Texas Instruments)

• Logic IC used in the ZX Spectrum (multiplexor chip at IC3/4 and IC25/26) and in some models of Spectrum 128

74LS32 Logic IC

• Logic IC for the ZX Spectrum (Quad OR gate at IC23)

7805 Voltage Regulator

Replacement 5 volt regulator IC for the Spectrum, (breadbin) Commodore 64, ZX81 etc

Diagnostic Test ROM for Spectrum 16/48

• Essentially the same as Switchable ROM Module (below), but supplied as standard with two different diagnostic programs installed (selected via a switch): Retroleum DiagROM and Brendan Alford's ZX Diagnostics.
• If the Spectrum PCB has a chip socket for the ROM you can simply swap the chip for this module to test the PCB, no modifications are required.
• A 28 pin DIL socket is supplied for where it is necessary to de-solder the ROM chip.
• This module has narrow pins so will not force the socket contacts open beyond their design specs.
• Please note: The module cannot be supplied blank because it requires a special interface for the EPROM burner.
• I have a simple external ROM board in the Peripherals section should that be preferable.

39SF040 EPROM for Harlequin 3H Board

• 32 Pin DIL EPROM Chip which can hold 8 ROM images (selectable with DIP switches on the Harlequin PCB)
• If programming is required please email me the ROM files after ordering, or confirm BLANK in the Special Instructions box if it is to be supplied unprogrammed.

LM1889N Video Encoder IC

• LM1889N Chip, as used in ZX Spectrum for colour encoding.
• Old stock parts - all tested by myself.
• Never soldered. Clean, straight pins.

Nebula - A Spectrum 16/48 ULA Replacement Module

• A plug-in PCB module designed to replace the ULA chip found in UK Spectrum 16/48 motherboards (versions 2 to 6) - Here's some fitting notes. Further info can be found here. 
• Includes a new 40-pin DIL socket, just in case the original is worn/unsuitable.

RAM Upgrade Kit for 16K ZX Spectrum (to 48K)

Comprises eight RAM chips (IC15-22), four glue logic ICs (IC23-26), wire links / solder and printed instructions. Fitting is usually just a case of inserting the chips into the empty sockets on the motherboard and soldering a couple of wire links across the appropriate pads on the PCB.

• 8 x 4164 Upper RAM chips (Unused, old stock chips in good condition - all tested by myself.)
• 2 x 74HCT157 (brand new)
• 1 x 74HCT32 ("")
• 1 x 74HCT00 ("")

This kit is suitable for Issue TWO and Issue 3 PCBs (the 16K Spectrum had been discontinued beyond those board revisions. Issue One Spectrums required a special daughter board to upgrade its RAM.)

Switchable ROM Replacement Board (No PCB mods required)

• For the original 16K/48K ZX Spectrum (only) - Can be installed permanently, soldered or plugged into a chip socket (a new DIL socket is supplied with the module, should it be required).
• Can hold two 16K ROM images, selected using a small onboard switch which can be accessed from Spectrum's expansion port so it is not necessary to open the machine to swap ROMs.
• Unlike when using a plain EPROM chip, no modifications to the Spectrum's circuitry are required when using this board - you can just desolder/unplug the existing ROM chip, replace it with this module and replace the original chip when done.
• Please let me know which two ROM images you require programmed onto the unit using the Special Instructions box during checkout, or email me afterwards. If nothing is specified, I will assume you require the standard ROM in slot A and DiagROM in slot B.
• Please note: The module cannot be supplied blank because it requires a special interface for the EPROM burner.

Lower RAM replacement module for ZX Spectrum

• A PCB module for replacing all eight of the Spectrum's 4116 lower RAM chips with its onboard low power SRAM IC.
• A slightly updated design (May 2025) - now uses round pins that fit into Turned Pin type sockets. This allows the module to be removed (and replaced with traditional chips again, should that ever be desired). It can of course be soldered directly to the PCB instead.
• Note: Not suitable for pressing into standard stamped pin type sockets as the module's round pins do not align well with these types of sockets.
• A kit with the lower RAM module and suitable sockets is listed below if required.

Lower RAM replacement module for ZX Spectrum with sockets

• As described above but also includes 8 Turned Pin Sockets allowing non-permanent fitting.

Upper RAM replacement module for ZX Spectrum

• A PCB module which replaces all eight 4532 ICs used for the upper 32KB of RAM in the Spectrum with its onboard low power SRAM.
• This is a slightly updated design (May 2025) which has round pins that fit best into Turned Pin type sockets (a kit which includes the sockets is available below). This means it can be removed / replaced with standard chips again later should that ever be a concern. It can be forced into stamped pin sockets though this may bend its pins slightly. Of course it can be just soldered directly to the PCB if you wish.
• Suitable for Spectrum motherboard issues 2-6
• Printed instructions are included with the board.

Please note: If you need to upgrade a 16KB machine which has not been upgraded to 48K before you will also need the support logic chips (order 1 x 74HCT00 for IC24, 1 x 74HCT32 for IC23 and 2 x 74HCT157 for ICs25+26 - these are listed above.)

Upper RAM replacement module for ZX Spectrum with Turned Pin sockets

• Upper RAM module as described above but also supplied with 8 Turned Pin sockets.

Z80 CPU - New

• Brand new Zilog Z80 Central Processing Unit for Spectrum (and ZX81, Amstrad CPC etc) 
• Modern lower-power CMOS version, direct replacement for NMOS originals.
• Replacing the CPU also resolves the known issue with out-of-spec Z80s sometimes found in Spectrums. (ie:  external interfaces not working correctly due to weak signals, usually "M1")

Z80 CPU -  Original, NMOS type - New, old stock  part

• Genuine vintage 4MHz NMOS Z80 chip from 1988 made by Goldstar - NOT a re-marked modern fake
• Has never been soldered
• Tested, working (/M1 signal good too)