tkc8800

Technology and retro computer blog

The ME2700 Orphan EPROM programmer

Over the last few years I've been looking for a modern and reasonably priced EPROM programmer to program early 2708 EPROMs.  2708's are used in the Cromemco 8k Bytesaver which is an early S100 PROM board that I use in my Altair 8800.  The Bytesaver itself can program 2708's, however I've never been able to get mine to do this reliably.  Most likely due to my Altair's ageing power supply.  So I need an external programmer to write EPROMS.

Up until now, I haven't been able to find such a programmer.  Most modern programmers don't support 2708's because of the odd voltages required for programming.  A work around I've used is to substitute 2708's with 2716's using an adapter (see that post here).  This made my Bytesaver board usable as 2716's are still widely supported by low cost programmers.  But I've always wanted to use the original 2708's in my Bytesaver.

Luckily such a programmer has now been developed.  Martin Eberhard recently developed the ME2700 Orphan EPROM Programmer which can program many old EPROMS including 2708's.  The ME2700 was made available through the Altair Yahoo group.  There was a limited supply of assembled units, and it was also made available as a kit.  I chose to get one as a kit.

The ME2700 kit contained the PCB, power supply and the chip containing the custom terminal software required to use the programmer.  The remaining parts were ordered through Digikey using a pre-defined parts list.  This made the process or getting all the required components quite easy.

I've been sitting on this kit for about six months, so I thought it was high time to have a go at assembling it.  I only have basic soldering and hardware diagnostic skills so I've been a little apprehensive to build the kit, as I've never soldered anything together with so many components.  This was partly the reason it took me so long to do it.  In preparation for building the kit I purchased a Hakko FX888D soldering station.  This is a medium level soldering station recommended for hobbyists.  I wanted to buy a decent soldering station to improve my chances of success with this kit.  It's also useful for my other retro machines as many of those need soldering work.

Workbench preparation
Workbench preparation
ME2700 bare PCB
ME2700 bare PCB

A PDF manual made available with the kit had excellent assembly instructions which I followed.  The first part of the assembly process was to place all the resistors and diodes onto the board, followed by all the chip sockets.  Being fairly inexperienced with electronics I triple checked the placement and orientation of all the components.  I knew I'd be better off getting things right the first time round rather than having to diagnose and repair.

Resistors and diodes installed
Resistors and diodes installed
Sockets installed
Sockets installed

The next part of the process was to add all of the other small components.  And then gradually adding the larger components until the board was complete.  Prior to installing any IC's onto the board a voltage check needed to be performed to ensure none of the IC's would be damaged by incorrect voltages.  I'm happy to say all the voltage checks succeeded first time.

Assembly complete
Assembly complete

Once the IC's were in place it was time to connect the ME2700 to my PC via serial link.  I have a couple of USB to serial adapters that I use, so I connected one to my PC and after checking all the settings I turned the ME2700 on and was greeted with the software banner!  I tested options in the software all seems to be working great.  I also tested reading in a couple of EPROM types and that worked fine as well.

ME2700 connected to pc
ME2700 connected to pc
ME2700 serial software
ME2700 serial software


Since the release of the ME2700 there is a firmware upgrade which adds a couple of features, so I'll look at doing this and in the next few days I'll look at writing to some 2708's.

2708 EPROMs
2708 EPROMs


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