4116 Spectrum "Lower RAM" Chip

• 4116 RAM (150ns) chips used for Lower RAM in ZX Spectrum
• Unused, old stock parts. Good clean condition and all tested for 2 hours before dispatch

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). The RAM type jumper settings on the PCB can be ignored 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 Spectrum 128 and grey 128 +2 (but not the +2A or +3)

74HCT00 Logic IC

• A cheaper, modern replacement for the 74LS00 logic IC in the ZX Spectrum

74HCT157 IC

• A cheaper, modern replacement for the 74LS157 logic IC for ZX Spectrum

74HCT32 Logic IC

• A cheaper, modern replacement for the 74LS32 Logic IC in the ZX Spectrum

74LS00 Logic IC

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

74LS04 Logic Inverter IC

As used in Issue 6A Spectrum motherboards and also on some models of Spectrum 128

74LS157 IC (Texas Instruments)

• Logic IC used in the ZX Spectrum (multiplexor chip) and in some models of Spectrum 128

74LS32 Logic IC

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

7805 Voltage Regulator

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

Diagnostic Test ROM for Spectrum 16/48

• Supplied with two diagnostic programs installed (selected via a switch): Retroleum DiagROM and Brendan Alford's ZX Diagnostics (if alternative ROM images are required please tell me which in the Special Instructions box during checkout).
• The module is Intended as a non-permanent tool for testing 16/48K Spectrum PCBs. The rubber key Spectrum case will not close with this module installed - Please see the item "ROM Replacement module - No PCB Mods" listed lower down for a similar unit that is intented to be left permanently installed.
• 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.

LM1889N Video Encoder IC

Replacement LM1889N Chip, as used in ZX Spectrum

Nebula - A Spectrum 16/48 ULA Replacement Module

The Nebula is a plug-in PCB module designed to replace the ULA chip found in UK Spectrum 16/48 motherboards (versions 2 to 6) - You can read more about it here. Here's some important fitting notes.

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

Comprises:

• 8 x 4164 Upper RAM chips (Unused, old stock chips - all tested by myself.)

.. brand new support logic chips for the upper RAM:

• 2 x 74HCT157
• 1 x 74HCT32
• 1 x 74HCT00

.. and 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. Almost all 16K models can be upgraded but there are some very early (Issue One) Spectrums that have no space on the PCB for more memory.

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

This version of the Spectrum RAM upgrade kit offers a cheaper, modern alternative to using individual DRAM chips. A small custom daughterboard PCB with a low power SRAM IC is simply pressed into the RAM IC sockets.

The kit also contains the 4 support logic chips which must be fitted at positions IC23-26 (IE: 2 x 74HCT157, 1 x 74HCT32 and1 x 74HCT00). A couple of wire links may also need to be soldered between the appropriate pads located on the PCB - full fitting instructions are provided.

Please check your Spectrum can be actually upgraded! Almost all 16K models can but there are some very early Spectrums that have no space on the PCB for more memory.

Click here for fitting instructions (printed version also included in kit)

If you don't require the support logic, the board is usually available on its own - see below.

ROM Replacement (EPROM) Kit for the Spectrum 16/48

It is possible to replace the Spectrum's ROM with an EPROM should it become faulty. However, a small modification must be made to the Spectrum PCB. This kit contains the necessary components:

• 1 x 28 pin 32KB EPROM
• 1 x 28 DIL socket
• 2 x schottky BAT85 diodes
• 1 x 10K resistor
• Instructions

One advantage of replacing the Spectrum ROM with a 32KB EPROM is that it allows two different ROM images to installed if desired (the ROM selection is based on the connections to the PCB - it's also possible to use a SPDT switch for selection, EG: See this video.) EG: Having a diagnostics ROM in the second ROM slot can be very useful. (Please see the Spectrum 128 section for ROM replacements for that machine - no extra components/mods are required there.)

VERY IMPORTANT:  You must email the ROM file(s) you wish installed on the EPROM and I'll burn them before dispatch- contact me for details. Note that the EPROMs I supply are write-once devices so cannot be reprogrammed once the ROM image has been burned. (If desired, the EPROM can be supplied blank for burning with a EPROM burner - just let me know in the Special Instructions box at checkout).

Switchable ROM Replacement Board (No PCB mods required)

• For the original 16K/48K ZX Spectrum - can be installed permanently (soldered or plugged into a chip socket).
• With this unit, either of two 16K ROM images can be 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)
• No Spectrum PCB modifications are required when using this board - you can just desolder/unplug the existing ROM chip and replace it with this module.
• 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.
• Please note: The module cannot be supplied blank because it requires a special interface for the EPROM burner.

Lower RAM replacement board for ZX Spectrum

A PCB module designed to replace (all 8) of the 4116 ICs used for the lower 16KB of RAM in the Spectrum.

Upper RAM replacement board for ZX Spectrum

A PCB module designed to replace (all 8) of the 4532 ICs used for the upper 32KB of RAM in the Spectrum.

• Suitable for Spectrum motherboard issues 2-6
• Modern low power SRAM
• Can be pressed into DIL sockets or soldered onto Spectrum PCB when the 4532s have been removed.
• Click here for fitting instructions - printed version also included with board.

Please note: If you need to upgrade a 16KB machine with this board, please purchase the version with the support logic chips.

Z80 CPU - New

• Brand new direct replacement Z80 Central Processing Unit for Spectrum (and ZX81 etc) 
• Modern lower-power CMOS version, made by Zilog.
• Replacing the CPU should resolve the known issues with the out-of-spec Z80s sometimes found in Spectrums. (EG:  External interfaces not working correctly due to timing anomalies and weak signals such as "M1")