BIG UPDATE: To celebrate the long running success of the v1 Adapter, I now present v2.
A carefully considered upgrade, which improves on many aspects of the time proven v1 Adapter.

Also, check out the special "Black & Gold Edition", which has now also been upgraded to v2.

If you already have a v1 Adapter, you might consider celebrating with me, by upgrading to v2. :)

New improved design TL866 Programmer Adapter!

Allows programming of the relatively large 42 pin (and 40 pin) 16-bit wide EPROM chips, popularly used for replacing original MASK ROM in 16bit devices like SNES & Sega consoles, Amiga computers, and many other cool Retro devices from the 16bit era.

The popular family of EPROM’s used for MASK ROM replacement (as they utilise a pin-out compatible with MASK ROM’s of the same size), include:

• 27C400 – 4Mb, organised as 256K x 16bit in a 40 pin DIP
• 27C800 – 8Mb, organised as 512K x 16bit in a 42 pin DIP
• 27C160 – 16Mb, organised as 1M x 16bit in a 42 pin DIP
• 27C322 – 32Mb, organised as 2M x 16bit in a 42 pin DIP

Also enables reading / back-up of those pin-out compatible MASK ROM's.

To allow programming these devices on the very popular TL866 series of USB EPROM Programmers, you simply insert this adapter into the TL866's 40pin ZIF socket and select the device to be programmed as the TL866 supported 27C4096 4Mb (JEDEC pin-out) EPROM. Programming is completed in 4Mb banks, selected via the Bank Select switch.

Why did I make this? (Original v1)

Back in 2017, when I needed to read some 16 bit Mask ROM's and program some 27C322 EPROM replacements, I searched for a suitable adapter for my TL866 USB Programmer. But, I could only find adapters which were based on tedious and human error-prone, binary DIL switch or jumper selections for the additional 3 address lines (required for accessing the large 42 pin 32Mb 27C322 etc.).

Aside from being unimpressed with existing adapters, they were also currently unavailable.

However, even if one had been available to buy, I likely would still have been driven to design a better, and easier to use solution!

This design incorporates a number of improvements over previously available Adapters:

• A simple and intuitive single “Bank Select” switch for quick, easy, and error-free selection of which memory bank to program (No tedious binary jumpers or DIL switches to toggle!).
• A clearly labeled slide switch for “Device Select”, for easy visual indication of the currently selected device.
• The Adapter’s ZIF socket is positioned over the TL866’s ZIF socket and sits nicely balanced, with the board edge nicely aligned with the edge of the TL866’s case.

Special "Black & Gold Edition" Option (2024 release)

The popular TL866II Plus Programmer was offered, for a short period, in a special Black Edition.

This special Black Edition includes a much higher quality "Aries" branded Zero Insertion Force socket.

To celebrate this, I've decided to offer a special "Black & Gold Edition" of my TL866 Programmer Adapter.

Full details can be found in the "Black & Gold Edition" Intro & Kitset Assembly Walk-Through video, and also in the Kitset Option bill of materials (listed below).

I hope you like this special "Black & Gold Edition" as much as I do.

TL866 EPROM Adapter v2 (New for 2025!)

It was way back in 2017, when I designed the v1 EPROM Adapter for reading and programming popular Retro 16-bit ROMs, using the low cost and hugely popular TL866 series Programmer (which many retro hobbyists have to hand).

As far as I know, this EPROM Adapter was the first one to implement my innovative "Rotary Switch" Bank select.

Given how my Adapter has helped many other retro enthusiasts with their own projects, over the last few years, I decided it would be fun to re-visit the design, and see if I can celebrate it by coming up with an even further improved v2 design.

Given the proven success of the existing v1 model, this would seem an interesting challenge.

So, I worked away in the background, and produced a "new improved design", that I was finally happy was a worthy successor!

Not to stop there, I then also made real use of the new design, regularly and exclusively, for a number of months, to further ensure that I was 100% happy that it was a worthy upgrade!

So, without further ado, I now present the EPROM Adapter v2.

The first thing you'll notice from the photos, is that I've chosen to go with a black PCB, instead of the standard green PCB of the prior version.

I decided the black PCB looked a lot nicer and gave a more finished look for this open PCB based product.

Now, apart from the PCB colour, the v2 Adapter includes the following enhancements:

• A more appropriate 8 position Rotary switch was chosen, to match the maximum 8 banks supported. This replaces the BCD / 10 position switch of the prior version.
• The Rotary switch has been upgraded to a 3:3 pin footprint package, to ensure optimal mechanical robustness. This replaces the 1:4 pin footprint of the prior version, where one side only had one pin mechanically securing the switch to the PCB.
• The surface-mount device count has been reduced from 7 components to just 5, improving the manual surface mount assembly efficiency.
• The Bank Selected EPROM Address pins are now nicely "logic gate" level driven, instead of just using direct-switched pull-up resistors. Making for a much more elegant solution.

Finally, despite this list of design improvements, the v2 Adapter remains at the same price as its predecessor.

I decided that even if there was some additional component cost, I would absorb this, so that there was no additional cost for end users.

In addition, the v2 enhancements have also been applied to the special "Black & Gold" edition. Combined with the new black coloured PCB, this makes the "Black & Gold" edition now really look the part!

Adapter operation verified with TL866CS, TL866A, and also with the later TL866II Plus model!

Adapter has been specifically designed to work with the popular TL866 series of USB EPROM Programmers (i.e. TL866CS / TL866A / TL866II Plus), but may also be applicable to other 27C4096 compatible 40pin EPROM programmers.

I'm offering as an Easy to Assemble Kitset, or Fully Assembled & Tested

To make the Adapter available at the lowest price, for Tindie hobbyists to easily assemble, I've packaged as a kitset requiring only the soldering of the through-hole parts.

The Adapter design includes tiny SMD (Surface Mount Device) components, which many hobbyists find difficult to solder without specialist tools. So, I've pre-fitted and tested the SMD components on the PCB!

Assembly of the remaining through-hole DIL socket, slide switch, specialist rotary encoded switch, and pin headers, should be straight-forward using just a regular electronics bench soldering iron!

If however you would prefer your Adapter Fully Assembled and Tested. Ready to Go! Then there is that option, for just a small additional assembly and testing fee.

Proven Design, but Kitset Assembly is obviously in you hands!

I have already sold many of these (all pre-assembled and QC tested), to retro gaming and computer enthusiasts, all around the world. All with 100% satisfaction and absolutely zero problems!

The design has also evolved through v1.0, v1.1, v1.2, and now the celebratory v2. Each version 1.x update was purely to satisfy my own perfectionist need to make small incremental tweaks to the design and board trace routing etc. And now, the carefully re-designed v2.0 is a celebration of the Adapter's long time success helping many retro enthusiasts around the world.

I think I'm finally done, and "perfectionist satisfied". :-)

Given the proven design, the only issue with introducing a Kitset version, is that I have no control over the final assembly that will be done by you!

So, I recommend you tackle the Kitset version, only if you have full confidence in your soldering ability, as you'll obviously also need to tackle any fault finding resulting from any dodgy soldering!

But of course, I'm sure your soldering skills are possibly even better than mine! And, it's all part of the fun of being a maker! :-)

YouTube Kitset Assembly Walk-Through / Adapter Intro & Demonstration Videos

• Original v1 Regular Kitset Assembly Walk-Through video here.

• Original v1 "Black & Gold Edition" Intro & Kitset Assembly Walk-Through video here.

• Original v1 Adapter Intro & Demonstration video here.

NOTE: The Adapter Intro & Demonstration video shows the original v1.0 flush "screwdriver only" Bank Select version, but is otherwise functionally identical.

A new video just covering the V2 release, is linked below.

More information can also be found at digicoolthings.com here.

What You Get

NOTE: Listing is for the v2 Adapter only, as shown in main photo. TL866 Programmer and EPROM is not included. Additional photos show TL866 programmer and EPROM only for illustration of Adapter usage.

"Regular" Kitset option includes:

• 1x v2 PCB with all SMD components pre-soldered and tested
• 1x 48-pin ZIF (Zero Insertion Force) DIL Socket
• 1x Rotary Encoded Switch (Bank Select)
• 1x DPDT Slide Switch (Device Select)
• 2x 20-pin SIL Header Strips (Programmer ZIF socket mount)

"Black & Gold" Kitset option includes:

• 1x v2 PCB with all SMD components pre-soldered and tested
• 1x High Quality Black Aries 48-pin ZIF (Zero Insertion Force) DIL Socket
• 2x High Quality Machined Round Pin 24-pin IC Sockets
• 1x Rotary Encoded Switch (Bank Select)
• 1x DPDT Slide Switch (Device Select)
• 2x 20-pin High Quality Round Pin Gold Plated SIL Header Strips (Programmer ZIF socket mount)

Assembled & Tested option includes:

• 1x Fully Assembled and QC Tested v2 Adapter (Ready to Go!)

Your Adapter is shipped in a robust cardboard carton with packing, for safe delivery via New Zealand International Air Parcel. Delivery target to most countries is 10 working days (BRAZIL buyers please refer note below!).

BRAZIL based buyers: Based on feedback, Brazil based buyers have experienced from 50 days to 113 days (PARANÁ state) for delivery. I am happy to continue to ship to Brazil based buyers, but please only proceed with purchase if you are happy to accept that delivery may take as long as 2 - 4 months! Thank you.

Buyer Feedback examples (v1):

"Better than other models I've tried! The rotary switch is SUPERIOR!”

"Thanks. It looks like you have the best design out there.”

"Amazing seller, great communication, well made product”

"Great seller, the shipping was super fast and the item is exactly what I needed."

"The most overkill packing of all time, zero chance of damage :0 perfect seller."