Agilent E3631A Repair (In Progress)

Created: October 5, 2026

Background

The college I went to had mostly Agilent/HP/Keysight test equipment. Even with all of their UI quirks I still enjoyed using them. I currently have a Tenma 72-6905 four channel power supply and thought it might be time to upgrade to something a little more professional and programmable. I’ll admit, I considered buying a new Siglent three channel power supply, but preferred a simpler interface (oh the irony).

The Hunt

It didn’t take me long to find multiple E3631As on eBay. I considered going for a different model like the E3632A or E3633A, but wanted something with more than one output (eventually I might get my hands on one of these other models). I found one that appeared to be in good cosmetic condition with a note stating that it produced an output and worked according. I decided to put in an offer and won the auction at $99 (not including shipping).

Arrival

When I unpacked the unit I noticed that the front panel had a chip in it from shipping. I wasn’t thrilled about that considering how good of shape the unit was in, but figured oh well. I planned on ordering some of the rubber bumpers to go around the unit anyway and it would cover up the imperfection.

However, upon further review I noticed that the front panel buttons were more recessed than I remembered. When pressing them in they could get stuck within the front panel itself. The button presses sometimes did not register with the unit. Great, exactly what I wanted…

Disassembly

I figured I would go ahead and disassemble the unit to clean it up and check out what is going on with the front panel. The inside of the unit looked pretty good (just a little dusty).

I finally got around to the front panel. Removing it from the unit was not difficult and I was able to pop the circuit board out from the panel itself. Here I went ahead and cleaned the button contacts and the rubber keypad membrane with isopropyl alcohol. After doing so I noticed the real issue. It appears someone maybe tried to take the unit apart themselves and broke the plastic panel where the rotary encoder is tightened around. This is what keeps the PCB flush against the panel itself. Without it button presses can push the PCB backwards resulting in my issue.

Potential Fix

I contacted the seller about these issues and they were generous enough to send me some money back to help pay for a replacement front panel. I found a few eBay listing from Shenzhen, China for E3631A replacement front panels that seems promising although a little pricey ($70 with $20 shipping). It comes with the plastic panel and the front sticker. Bad news is that it will take a few weeks before it arrives.

Going forward with this repair will require me to desolder the wires and capacitors connected to the banana jacks before removing them entirely (other models do not require this step as the front panel can be removed without disconnecting the banana jacks). A great reference video is from Ian Johnston who has multiple Agilent/HP/Keysight repair videos on his channel.

Future Work

I ordered the new front panel from eBay, but it is supposed to take a few weeks for it to arrive. I will update accordingly.