These are simple devices, which is good news when something goes wrong. A light source, a battery compartment, a switch and a moulded grid is the entire machine. Most failures come from one of four places, and three of them are fixable at the kitchen table in ten minutes.
Nothing happens at all
Start with the obvious and check it properly rather than assuming. Batteries in the right orientation, fresh rather than partly used, switch fully engaged, and the compartment screw done up, since a loose lid can hold the contacts apart. Try a known-good set of cells before concluding anything.
Pegs no longer grip
Holes get reamed out when pegs from another generation are forced in. Once the grip is gone it does not come back, and packing the hole is not worth attempting. If several areas are affected, the board has reached the end of its life; confirm that any replacement takes the pegs you already own by checking the range at https://lite-brite.net/.
Flickering or dimming on one side
Usually a contact problem. Take the cells out, look for dull or dirty springs and plates, and rub them gently with a dry cloth or a pencil eraser. If you see green or white crystalline residue, a cell has leaked; clean carefully, avoid touching the residue with bare skin, and wash your hands afterwards.
The panel works but the picture looks dull
Often it is not the light at all. Dust in the holes, a sheet that is not sitting flat, or a glossy paper substituted for matt black will all wash the picture out. Check the paper before blaming the electronics.
What not to attempt
Do not open a sealed LED panel, do not attempt to replace individual emitters, and do not repair a mains lead with tape. On a battery unit there is essentially nothing serviceable behind the light diffuser, and the risk of cracking the housing is high.
Sensible spares to keep
- A matching set of batteries, all replaced at the same time
- A small cross-head screwdriver that fits the compartment screw
- Black sugar paper for replacement sheets
- A soft dry brush for clearing dust from the grid
- A pot of spare pegs bought for your specific model
Coin cells deserve a separate mention
If a remote or a small module in your set uses button cells, treat a loose one as a hazard rather than a spare part. Swallowing causes serious internal burns within hours, so keep them sealed and out of reach, and seek emergency medical help immediately if you suspect one has been swallowed.
Deciding to let it go
A cracked grid, a corroded compartment that will not hold a cell, or a damaged mains lead means retirement. Keep the pegs, which usually outlive the board and may fit a replacement in the same line, and recycle the electronics properly rather than putting them in the bin.