Upgrading Synertek Systems KTM-2 to a KTM-2/80

KTM-2 Modifications

With an EPROM programmer available and a little electronics know how, this article will attempt to help the reader upgrade a KTM-2 to a KTM-2/80 terminal. It should be noted that users with KTM-2's with a serial number prior to 0733 CANNOT perform these modifications. The actual modifications will require you to cut a trace on the board, add a jumper, install 5 IC sockets and chips, and replace the existing system ROM. You will also have to change some other jumpers to accommodate the new system and character EPROM depending on what EPROM you use. I personally changed the original 2 K system ROM with a 2732, 4 K EPROM. The lower half of the 2732 contains the KTM-2 code and the upper half contains the KTM-2/80 code. I used a 2716 EPROM for the character generator and no modifications were necessary to the board. The 2716 and original character ROM in the KTM-2 have identical pin outs. U-22, the original character generator is simply duplicated for U-23. By adding a DPST switch, you would be able to switch between either the 40 or 80 KTM-2 system modes.

The files located here contain the binaries for both system and character ROMS that I currently use and the original KTM ROM's. My ROM's have been changed to accommodate the 60 key keyboard I currently use instead of the KTM-2's 54 keys. The system ROM mapping for the keyboard matrix was changed to reflect these new keys and the character ROMS were also altered for these changes. NOTE - the 60 key binary files will not work with any original KTM-2 or KTM2/80 as the keyboard encoding mapping has been altered for my keyboard. You may also download the source code.txt or using the SYM Link program, download the source code.rae file and assemble the code to generate your own boot ROM. If you decide to download the binaries you can click here to find out how to re-map the keyboard matrix. Assuming you have an EPROM burner, you can always copy your original character ROM (U-22) and burn a duplicate that will be needed for U-23. If you want to change the blinking block to a blinking line, download the original binaries with the modification already made for you. You will also need four chips to complete the upgrade. They are 1 - 74166 (U-28), 2 - 2114 (U-17 & 18) and 1 - 8304 (U-35). You may also consider putting in sockets instead of soldering the chips directly into the board.

The first step will be to cut a trace on the KTM-2 board. The trace is located to the right of U-27 and should be labeled J-2. This trace goes between the marked J2 location and the number 40. Your board may have a jumper installed or the trace. After cutting the trace a jumper needs to be installed between the J2 location and the number 80 hole. If you decide you want to switch between the 40 or 80 character mode, click here or simply install the jumper. Once this is completed, it is now necessary to install the IC sockets and chips. You will have to change other jumpers to properly chip select your particular EPROM. A complete schematic, located here, will help you locate these jumpers. If you decide to copy your original character ROM, do so and then install it in the U-23 socket. Install the balance of the IC's. The last thing to consider is what boot ROM you want. If you only want the -80 code, simply download the 2K binaries and burn the chip. If you decide to dual-ize the KTM, download the 4K version. In either case, jumpers will have to be re-arranged to accommodate the new chip.

Be sure to double check your work as I cannot be held responsible if it does not work properly. I can say that I have done the above procedure and had no problems of any kind.

The following jumper changes will complete the upgrade. I am not sure of the original jumper location default setting as I no longer have my original KTM. I do know the original character generator ROMS have identical pin outs of the 2716. The boot ROM on the other hand is a different story as pins 20 and 21 are both positive chip select and that pin 18 was grounded. The chart below will show what jumpers to change and what to make them depending on the EPROM.

  Pin #             2716                     2732

   18                 J-11                      J-11        Connect to pin 8 of U-32 (should be one connection at J-19)

   20                 J-19                      J-19        Connect to ground (should be "G" on board at J-11)

   21                 J-18                    see note     For 2716, connect to +5 volts located at J-18.


NOTE: If dual-izing the KTM connect pin 21 ( A-11 ) to common of switch as shown here. If pin 21 is low, the lower half of the 2732 is selected and if high, the upper half is selected. The lower half will be the KTM-2 and the upper half will be the -80.