April 25, 2020 Test Equipment, HP 35665A

HP 35665A all options

Enable all options on an HP 35665A

References/links:

24C01 datasheet
Arduino library used from Julien Le Sech
Memory chip used
A collection of manuals and utilities for the 35665A from KO4BB

Unfortunately when I got my 35665A almost no options were installed. I especially wanted the HP Instrument BASIC option to automate my measurements.

According to the internet I need to write the following data to a 24C01 EEPROM. Then replace the one in the motherboard.

    00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 
00: 00 13 20 5D 04 05 06 00 08 09 48 50 33 35 36 36 .. ]......HP3566
10: 35 41 20 20 33 34 34 35 41 30 32 36 36 36 1E 1F 5A 3445A02666..
20: 20 21 00 76 76 76 76 76 76 19 2A 2B 2C 2D 2E 2F !.vvvvvv.*+,-./
30: 48 45 57 4C 45 54 54 2D 50 41 43 4B 41 52 44 20 HEWLETT-PACKARD
40: 33 35 36 36 35 41 20 44 59 4E 41 4D 49 43 20 20 35665A DYNAMIC
50: 53 49 47 4E 41 4C 20 41 4E 41 4C 59 5A 45 52 20 SIGNAL ANALYZER
60: 60 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F `abcdefghijklmno
70: 70 71 72 73 74 75 41 77 78 79 7A 7B 7C 4D 48 99 pqrstuAwxyz{|MH.

Programming a new EEPROM

So I bought a few chips and built a programmer. Then I started testing Arduino libraries until one worked. This is the quick and dirty code (you need to install this library):

If everything went well you should see this on the serial terminal:

Writing to EEPROM memory...Done.
Reading from memory...
    00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00: 0  13 20 5D 4  5  6  0  8  9  48 50 33 35 36 36 
10: 35 41 20 20 33 34 34 35 41 30 32 36 36 36 1E 1F 
20: 20 21 0  76 76 76 76 76 76 19 2A 2B 2C 2D 2E 2F 
30: 48 45 57 4C 45 54 54 2D 50 41 43 4B 41 52 44 20 
40: 33 35 36 36 35 41 20 44 59 4E 41 4D 49 43 20 20 
50: 53 49 47 4E 41 4C 20 41 4E 41 4C 59 5A 45 52 20 
60: 60 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 
70: 70 71 72 73 74 75 41 77 78 79 7A 7B 7C 4D 48 FF

Changing the EEPROM

Now to change the EEPROM you need to open the case, lift the power supply and take the memory board out. Dave Jones made a repair video of a similar analyzer (35660A). Watch it before you start.

Disassembly instructions

And since you have the RAM card out maybe it's a good idea to change the battery too.