Paul Hempshall

Website Cyber Security Professional

Replacement HCB107C-1 PSU Adapter Cable

Published: August 28, 2023 10:03 pm
Updated: October 8, 2023 12:45 pm

Write-Up Guide

I acquired a height-adjustable desk from an ex-display salvage auction for £22. It is the Logik LPOWER21 that uses components manufactured by the Chinese company Loctek. It was missing the AC power supply, control box adapter cable and bolts. Unfortunately, spare parts are unavailable. I was on my own to hack something together to get this table working again. This post describes how I found and made a suitable replacement.

You may find this post suitable for other desks using the same control box, such as the FlexiSpot E1/EG1/EC1 or the FoxGear FG-ED-45.

After some Googling, I found the user manual, enabling me to confirm the missing parts: bolts (M6 size), power supply, and power supply adapter cable.

The first thing I need to figure out are the power supply requirements and the adapter cable pin layout.

Back of the Loctek HCB107A-1 controller box.
Back of the Actuator Motor MBC-24H68B.

As we can see, the input and output of the controller box are 19—33vDC, and the rated load of the motor is 24vDC. Googling for replacement power supplies kept leading me to recliner chairs. These power supplies are 29vDC 2amp, and all use a strange connector. This connector is an S-Type DIN 41529.

Referring to the manual, we can see that the power supply uses the same S-Type DIN 41529 connector. The technology in a recliner chair is the same as a height-adjustable table: a control box and actuator motor. The adverts for these power supplies suggest compatibility with chairs, beds, tables and window blinds.

PSU Connection from the manual.

We need a little more certainty before ordering a cheap knock-off power supply. So, let's examine the circuit board of the controller.

Top side of HCB107A-1 controller PCB.
Back side of HCB107A-1 controller PCB.

On the top side of the PCB we can see two 24v relays. This voltage correlates with the rated load of the actuator motor. On the reverse of the PCB we can see a 29v track from one of the DC IN pins. This Reddit thread suggests that their PSU is 29v 1.8amp. I went ahead and purchased a 29vDC 2amp power supply for a recliner.

The DC IN connector, I recognise from years of building computers. It's a Molex 4-Pin, the same that is on ATX power supplies. To find the pin layout of the power connector, we can use a multimeter in continuity or diode mode to see where the pins and PCB traces connect to.

I tested each pin and found that:

  • Pin 1+2: Did not trace to any component or any ground points, confirming that these two pins are unused.
  • Pin 3: It traced to one of the relays along the 29v line on the PCB.
  • Pin 4: Had continuity to each of the ground points.

Please note that the circuit board depicted below is upside down relative to the mounting position of the control box underneath the desk. Additionally, please refer to the Molex SD-5557-003 datasheet to understand the pin layout.

Pin layout of DC IN connectors for HCB107A-1.
HCB107C-1 controller enclosure with power supply.

I have a bunch of salvaged connectors from an old computer PSU, and with a bit of modification (chopping off the off-centre retaining clip and cleaning up the sides), I found a connector that fit.

I purchased a power supply extension cord to make the power supply-to-control box adapter cable. I then chopped off the DIN 41529 connector from this cable. Then, I soldered the wires from the salvaged Molex connector. Finally, I made sure to insulate the bare wires with heat-shrink tubing.

You can use two staples and some pliers to remove the wires/pins from the Molex connector.

Stripped extension cable and salvaged Molex ready for soldering.
Testing to make sure the cable colours are correct - brown/positive and blue/negative.
Preparing the wires for soldering - splay the wires and then twist.
I decided to swap one of the yellow wires to a black wire for +/- reference.

I used a lot of heat-shrink tubing. Each wire was individually insulated, then insulated together, and finally, around the connector. The connector on this cable doesn't have the retaining clip (I cut it off the spare because it was off-centre). If I remake this cable, I will purchase a replacement Molex connector and keep the wires short, making it look tidier.

The finished adapter cable.

After an evening of research and diagnosis, I have a working £150 desk that cost me £35 (table and parts).

Parts List

Here are a list of parts that you can use. You can find these cheaper directly from China but with a longer shipping time.

Power Supply:

Extension Cord:
I cannot find the connectors for these extension cables so have to use a pre-made extension cable. Also, this cable may not be necessary if the cable from the power supply is long enough to reach the control box. You could splice directly into that cable instead.

Square Plug: Either Molex 39-01-2040 or AMP TE Connectivity VAL-U-LOK 794954-4.