Earlier Z1 grinders shipped with a motor circuit board (PCB) that has three large capacitors. We have since released an updated board with two capacitors and no ionizer plug. Most owners complete this at home in under an hour with the tools from their service kit.
This guide covers how to tell which board you have, what is different on the updated board, and how to install it.
Is this upgrade for you?
This upgrade applies to Z1 grinders that shipped with the earlier board, which has three large capacitors. Step 1 below shows how to check which board you have. Grinders with the two-capacitor board already have the update.
If your grinder simply will not turn on, start with Troubleshooting: Z1 Will Not Turn On (Replacing the Fuse). If it only stalls while grinding beans, see Troubleshooting: Z1 Stalls, Struggles, or Stops With a Loud Noise.
Step 1: Count the capacitors on your board
Unplug the grinder first. Remove the two 3mm screws on the back of the grinder and slide off the rear housing. Look at the circuit board for the large cylinders on your PCB board marked 400V 150µF. These are the capacitors.
Three capacitors: you have the older board, and this guide applies to you.
Two capacitors: you already have the updated board, so no upgrade is needed. If something seems off, send a short video to info@zerno.co so we can help you find the cause.
What is different on the updated board
Two capacitors instead of three
The missing third capacitor is intentional. Our earlier boards were built with an extra capacitor we did not need, and over time it could put stress on the PCB. The two-capacitor design is more durable.
Do not solder and move the third capacitor from your old board to the new one.
No plug for the ionizer
Earlier Z1 grinders have an ionizer near the spout that plugs into the old board. The updated board has no ionizer plug, because we retired the ionizer. In our testing, the anodized one piece chute and a quick spritz of water on your beans (RDT) control static better than the ionizer did, with less clumping.
The ionizer wires will have nowhere to plug in after the swap, and that is expected. Tuck them safely away from the motor and other moving parts, as shown in the Turning Off the Ionizer video. You do not need to solder anything or transfer parts from the old board.
Why the switch gets replaced too
We send a new switch with every updated board so both parts are new and matched. Installing them together gives you the best long-term reliability.
What you need
- An updated Z1 PCB that matches your grinder's voltage (120V or 220 to 240V). The boards are different, so the voltage must match. See Power Cord and Plug Type for Your Z1 and Using Your Z1 in Another Country (Voltage).
- A new Z1 power switch.
- The 2.5mm hex driver and 3mm hex key from your service kit. Newer kits include Wera tools; some older videos show the earlier screwdrivers, and either works.
- Flush cutters or nail clippers, only if you need to trim the motor plug (see Step 3).
- Your phone, to photograph the wiring before you unplug anything.
To get an updated PCB and switch, email info@zerno.co with your order number or serial number, your grinder's voltage, and a photo of your current board showing the capacitors.
Videos
Motor and PCB disassembly (main walkthrough): https://www.youtube.com/watch?v=Lkvc21aNzhw
Switch replacement: https://www.youtube.com/watch?v=Jm2RdVY1cbY
| Video | Link | When to use it |
|---|---|---|
| Z1 disassembly | https://www.youtube.com/watch?v=BohoSmx_Dp0 | Full disassembly overview |
| PCB replacement | https://www.youtube.com/watch?v=U1hLSt5VkgI | Another view of sliding the new board into place |
| Turning off the ionizer | https://www.youtube.com/watch?v=djXzCf2Oxro | Earlier Z1 grinders with an ionizer |
| Rear and front assembly removal | https://www.youtube.com/watch?v=xc98jKv9wMg | About 2:25: where the small bar on the motor shaft goes |
Step 2: Install the updated PCB and switch
Do not open the grinder while it is plugged in.
- Unplug the grinder and let it sit for a few minutes before touching the board, since the large capacitors can briefly hold a charge.
- Remove the two 3mm screws on the back and slide off the rear housing. Housings on earlier grinders fit snugly. Pull straight back with even pressure, and avoid prying with a screwdriver, which can mark the finish.
- Before you unplug anything, photograph every connector on the old board from a couple of angles. You will use these photos to match each cable to its socket on the new board.
- Remove the old board, following the motor and PCB disassembly video. If a small magnetic bar falls out when you pull the motor, it belongs on the motor shaft (about 2:25 in the rear and front assembly removal video). A tiny dab of petroleum jelly holds it in place while you reinsert the motor.
- Replace the switch, following the switch replacement video.
- Install the updated board and reconnect each cable to its matching socket, using your photos. If your Z1 has an ionizer, its wires will have no socket. Tuck them away as described above.
- While the rear is open, check the fuse. If it is blown, replace it with the spare from your service kit (5A 250VAC time-delay).
- Reassemble the grinder. If the assembly will not slide back on, the auger key is usually not lined up. See about 2:05 and 3:55 in the disassembly and reassembly tips video.
Step 3: Test before you grind
- Turn the dial coarser so the burrs are not touching.
- Plug in and run the grinder briefly with no beans. It should spin smoothly to full speed.
- Add a few beans and confirm they feed down into the burrs. If the beans sit on top of the auger and do not feed, the motor is running in reverse. Unplug the grinder and flip the motor plug around on the board. If a small plastic tab stops the plug from fitting the other way, trim the tab with flush cutters or nail clippers. This is safe, and the plug still seats securely.
- Rezero your grinder. See Setting the Zero Point on Your Z1.
Common questions
My new board has one less capacitor than my old one. Did I get the wrong part?
No. The updated board has two capacitors by design.
My new board has one less plug than my old one. Where does the extra cable go?
That extra cable is the ionizer. The updated board has no ionizer plug, so tuck the wires away and leave the ionizer off.
Will I get more static without the ionizer?
Most owners notice no difference, especially with the anodized one piece chute and RDT. See Z1 Grind Settings, RDT, and Retention for static tips.
Can I install only the new board and keep my old switch?
We recommend replacing both, so the new board and switch are matched.
Can I add the third capacitor or the ionizer plug from my old board?
No. The updated board is designed to work without them, and adding parts back can undo the durability improvements.
Still having trouble?
Please do not disassemble further than this guide describes. If these steps do not work, please contact support at info@zerno.co and include a short video of the grinder running and a photo of your board.