4116 RAM Chip

• 4116 RAM (150ns) chips used for Lower RAM in ZX Spectrum
• Unused, old stock parts (Texas Instruments / Mostek brand)
• All tested 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.

41464 RAM Chip

• Organization: 64K x 4
• Speed 120ns
• NEC brand
• Package: 18 pin DIL
• All tested before dispatch.

As used on late revision motherboards of Commodore 64, Spectrum 128 +2A/+2B/+3 

Will also replace 4464 type RAM ICs.

4164 RAM Chip - Texas Instruments Brand

• Organization: 64K x 1, Speed: 150ns or faster. Package: 16 pin DIL
• Unused, clean, old stock parts (condition as new - all chips tested before dispatch)
• Texas Instruments brand.

This chip will replace:

• Upper RAM chips in the ZX Spectrum 48K (Replaces TMS4532-15NL3, TMS4532-15NL4 , OKI M3732H-20 etc)*
• Spectrum 128 RAM chip (RAM in 'toast rack' 128k and in early 128 +2s) 
• Commodore 64 RAM chips (most 'breadbin' models use 8 RAM chips. Note: The 64C uses 2 x 41464)

*  These 4164 chips serve as a universal replacement for all the different types of UPPER RAM chips originally used in the Spectrum 48K - IE: You can use these to replace any number of bad chips at IC15-IC22 no matter what type of chips were originally installed (and the configuration links can be left alone). Please note: 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 48 PCB.

Faulty RAM chips in the C64 often result in an "Out of Memory" error on boot or less than 38911 bytes free. In the Spectrum, when the upper RAM is bad the system will often boot faster and work as a 16K machine. One crude but often effective way to test which chip is bad, 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.

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

74LS157 IC (Texas Instruments)

• Logic IC used in the ZX Spectrum (multiplexor chip)

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

LM1889N Video Encoder IC

Replacement LM1889N Chip, as used in ZX Spectrum

Nebula - A Spectrum 16/48 ULA Replacement Module

The Nebula is a small plug-in 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.

Availability is few and far between as I solder them by hand and my time is limited.  There's usually a few listed every week but they do sell quickly - If out of stock, drop me a line and I'll email you when I have more listed. Sorry, I cannot reserve them.

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

Comprises:

• 8 x 4164 150ns Upper RAM chips (Unused, old stock Texas Instruments brand - all tested before dispatch.)

.. 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.

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.

Spectrum ROM Replacement Kit

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.

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.

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

• 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")