Cleaning up and looking at a bunch of plug-on modules for my Hewlett Packard 5300B mainframe modules, after purchasing a new unit. It seems that I am starting to collect quite the range of modules for my HP 5300 systems since my original 5300B Measuring System back in 2017.

The newest addition to my HP 5300 series modules is the 5312A HP-IB Interface plug-between module. It is also referred to as the “ASCII Interface” module, and plugs between the 5300B mainframe and associated plug-on modules to provide an interface to the Hewlett-Packard Interface Bus (HPIB). The available data includes: all significant digits, exponent, overflow, and function codes. It is capable of transferring up to 40 measurements per second depending on the plug-on module attached. It is not compatible with the 5300A mainframe.


The board to board connector is hand soldered to the PCB using short wires for the needed connections. The operation of the 5312A is controlled by an Algorithmic State Machine (ASM), and uses a 4K ROM to output 16 bits to control the ASM.

The back panel includes the HP-IB (GPIB) connector and a DIP switch for selecting the address, mode, shield enable, and a “self check” function.

Another plug-on module that I have several of is the HP 5308A 75MHz Timer/Counter plug-on module. It is another module that is only compatible with the 5300B mainframe module. It has two channels and a SEP-CHK-COM switch that connects the Channel B connector on the front panel to both A & B amplifier circuits in parallel. There are lots of functions including a self-check and stopwatch.


The combined front panel switches are used to select the address of ROM U26 which then set 16 output lines, which control the signal path and logic including the decimal point, annunciators, and resolution. The 5308A also features an automatic time base mode.


Both of my 5308A modules have worked well with no issues other than requiring a good cleaning of the switches with DeoxIT contact cleaner to restore full functionality.
Connected to my 5300A mainframe is a HP 5302A 50 MHz Universal Counter plug-in module. It is a much simpler counter than the other modules that I have, but still has some good features. The A channel accepts up to a 50 MHz signal, while the B channel has a maximum of 10 MHz input frequency. It has frequency, period, time interval, ratio, and check functions.


Compared to the higher frequency capable modules, the circuit board is a much simpler design. The input circuitry for channels B and A are located in the upper-left area of the circuit board in the image below, and show a similar component layout for each channel.



My recent purchase included a 5300B mainframe module that is a 1824 series unit with 1974 dated components installed. My other two 5300b“s are newer 1452 and 1704 series units. I noticed that the older series 1824 unit had some different branded, colored, and shaped components used in it, mainly capacitors.


I really have been enjoying repairing and learning about the HP 5300 systems over the past few years. Luckily documentation is still available for all the modules I currently have.
I am still looking for a 5306A Multimeter Counter, and a 5307A High Resolution Counter module which should both also be a learning experience.
Hi,congratulations on your work. I have an HP 5308, which has a faulty IC. Part No. 1820–1565 but I can’t find it. I have to find a correspondent, can you help me out.
Hi Gianni,

Looks like IC U2 (1820–1565) is a dual ECL Schmitt trigger.
The closest modern equivalent that I have found is a Maxim MAX9693, but it has a different pinout and would need to be adapted to work in the circuit.
Greg (Barbouri)
Hello Mr. Barbouri, I am in possession of a counter/timer type 5308A which unfortunately does not work well, because it takes a long time to display a frequency and when it wants. Do you have the schematics for modules 5300 and 5308A to help me with my repair? I can’t find these schematics because this material is no longer tracked and has become obsolete. Thank you very much in advance for your response and congratulate you on your high-quality work. John
Hi Jean,
The 5308A manual is available for purchase from http://www.artekmedia.com, which is where I purchased my copy of the manual.
The 5300A and 5300B display mainframe manuals are available online from https://www.keysight.com/us/en/assets/9018–05899/user-manuals/9018–05899.pdf
and https://xdevs.com/doc/HP_Agilent_Keysight/HP%205300B%2C%205310A%20%20Operating%20%26%20Service.pdf
Also be sure and checkout my post on building the 5300 test / diagnostics card:
Hewlett Packard 10548A Diagnostic Service Kit
Greg (Barbouri)
Hi Greg, thanks to your invaluable help, I have found some interesting documents on the 5300 B module that is part of my device. For the other part (5308A), I’ll see if it’s worth ordering the documentation, because indeed these modules are difficult to access and not so easy to repair. I looked at your page: Hewlett Packard 10548A Diagnostic Service Kit and indeed, I understood that you need some diagnostic tools to make a successful repair.
Your website is really good and very well done and it is a great help for repairs, ideas for realizations and information. It’s perfect and amazing. Thanks again Greg for your help. John