[Fixed] No LED light on Logitech K750 Keyboard

K750 charging under a lamp

tl;dr: Use a combination of a bright light and the reset technique (off ? CAPSLOCK + some keys ? on)

Background

A few years ago while on holiday in sunny SC — a lovely place to visit, incidentally — I took the opportunity to purchase a Logitech K750 keyboard. The K750 was is a ‘solar’ keyboard- no changeable batteries, only solar cells to power it. I had been frustrated by other keyboards which needed battery changes timetabled in accordance with Sod’s Law.

They keyboard got passed on to my folks and all was well. However, since my dad passed away my mum has not used the computer as much, and so the lights in that room haven’t been on. When I went to use the computer there recently the keyboard was completely dead. Not even the red ‘sad face’ LED would light even if held close to a light source, which would normally elicit some response.

Leaving the keyboard in a decent amount of ambient light for a few days seemed to do very little to help.

Revivifying a K750

Enter Nut and his Tech, wherein they describe the reset procedure:

1. Turn off the keyboard.
2. While holding onto CAPS lock, keep pressing a few keys for the next 5 or more seconds.
3. Turn on the keyboard.

I did the above and held the K750 very close to a fairly bright bulb, and the LEDs sprang to life!

First the green happy face when still next to the light, then the red unhappy face when I took it out of full illumination.

So it works, for now. I was even able to type from the next room over where it sits charging beneath a mini anglepoise-type lamp.

On Cheap Hardware and Misbehaving Monitors

tl;dr: Cheap stuff can malfunction in unusual ways

I have a history of buying cheap hardware out of necessity. This has not changed in more than ten years. I wish it was different; but scrimping and saving and buying cheaper, off-brand is the only way I can afford to do things. That said, I am lucky be able to afford what I can afford, it is definitely more than some who are less fortunate.

I have a triple monitor setup, which some might call an unnecessary luxury; but with my eyesight being what it is more real estate means being better able to both fit a reasonable amount of things on the screens at a reasonable visibility.

Each of the three displays is 27″ and capable of a resolution of 2560×1440 at 60Hz. They are all also ‘cheap’ (relatively speaking) Korean knock-off imports- brands such as PCBANK, Crossover and DGM- the last of which I have at least come across before, in the form of the cheap TFT monitors referred to in the post linked at the start. At least they have a track record!

The third thing that these monitors three have in common is a tendency to malfunction; each in different ways. Taking them in the order of purchase, which dates from about five or six years ago to less than six months ago:

  1. PCBANK – The only one I bought new. Makes an audible noise when displaying white or mostly white (eg a a mostly text web page, such as Wikipedia). Also occasionally displays a distorted image for half a second before coming to its senses.
  2. DGM – intermittently blanked itself under Windows
  3. Crossover – If turned off or doing into standby, won’t turn back on for 5-20 minutes. Possibly a backlight issue. As a bonus, it was bought second hand and came with its integrated plastic monitor stand removed; the only way I could see to reattach it would be to separate the plastic casing, which I got halfway to doing before I figured I would purchase the monitor mount[s] I had been intending to for years

In addition, the transformer for the PCBANK or DGM monitor developed a fault which made my speakers screech like a banshee requiring me to take the highly-technical step of moving the transformer further away. Then it started buzzing itself, and needed replaced.

Those transformers are beasts, incidentally- 24V 5A or 120W.

These faults range from irritating to intolerable, but I reckon that if I had three monitors from reputable manufacturers at a commensurate price, I wouldn’t have the same issue with malfunctions.