I had no documentation for my NEC TK-85, so I had no idea how to use it. I decided the best thing was to do some web research. Eventually I found a document in Japanese which includes a simple program that continuously streams a dash mark across the LED display, and a brief description of how to install it, save it, and load it back. Here is my translation of that document into English:

Enter a program

Make sure the toggle switch is set to STEP

Type [8] [0] [0] [0] (that’s ‘8000’. The square brackets represent individual keys pressed)

Then press [ADRS SET]

Type in the following (*not the addresses in grey):

8000: 21 F8 83   

8003: 3E 08      

8005: 36 40      

8007: CD 14 80   

800A: 36 00      

800C: 23         

800D: 3D         

800E: C2 05 80   

8011: C3 00 80   

8014: 16 40      

8016: 06 00      

8018: 05         

8019: C2 18 80   

801C: 15         

801D: C2 16 80   

8020: C9  

Flip the toggle switch to AUTO

Type [8] [0] [0] [0] then press [ADRS SET]

Then push [RUN]

Save to cassette

Press [MODE] [SAVE] Then a single LED dot appears

Type [0/AF] [1/BC] [WR/ENT] a single LED dot appears again

Type [8] [0] [0] [0] [WR] [8] [0] [2] [1] (‘8000.8021‘ should be displayed )

Start the cassette 'recording' then press [WR] 

Wait for the LED to finish its counting as the data is saved.

Load from cassette

Press [MODE] [LOAD] Then LED dot appears

Type [0/AF] [1/BC] [WR/ENT]

Press 'play' on the cassette deck and wait again for the LED screen to count as the data is loaded

Flip the switch to AUTO 

Type [8] [0] [0] [0] (or another starting address depending on your program)

Then press [ADRS SET]

Then push [RUN]

neoncluster.com