Hot-rodding a Keithley 2304A power supply

I’ve been lucky enough recently to score a Keithley 2304 power supply off ebay for a measly $75. For those unfamiliar, these are high speed battery simulator units capable of measuring very low currents and also behaving like a battery and sinking current.

Original ebay picture

Original ebay picture

After the usual dusting off and alcohol wipe, I found the unit to be in a good shape despite being made in mid 1990s. The screen on the other hand was a different story- 20 year old technology meant pretty lousy contrast and viewing angle.

After taking things apart and finding a standard character LCD display, all I had to do was find a mechanical match with the same pinout and 5V operation. An ERM1602SBS-3 from  fit the bill and was also blue- an added bonus. The swap went pretty well, but I found the default contrast voltage of the original divider was not a very good fit for the modern display. So in went a potentiometer I had handy. (I did remove original divider resistors R624/R625  first)

Display soldered, added potentiometer for contrast


While inside I also added proper binding posts to the front of the unit. By default all connections happen through a terminal block on the back- good for rackmount use, bad for benchtop)

UI board reinstalled and binding posts wired in

After putting it all together, we now have a much more modern looking power supply with the front binding posts and shiny blue display:Much better screen readability


EEVblog thread on these units



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