using old laptop bricks for Train Accessory power?

I see no reason why you not.  It's just another dc power supply.   The big issue is that there is no built in circuit breaker like most hobby transformers.  This may not be a problem for lighting circuits.

You bet, cheap power.  Note that some accessories need AC power, those wouldn't be compatible.

I used a laptop brick to power my Bachmann G scale 4-6-0 before I converted to BPRC, ran great.  I used the laptop battery to power my old Aristocraft Train Engineer ART-5470.

Does anyone know if you could use the laptop brick to power Miller Engineering signs?

@Joe K posted:

Does anyone know if you could use the laptop brick to power Miller Engineering signs?

As long as it's 4.5v DC and is rated for the current draw.

Very few powerpacks will be exactly 4.5V, so probably no.

Most notebook power supplies output 19v.  You need a DC to DC step-down converter (discussed in many threads) to drop the notebook supply voltage to what your accessory needs.

Years ago, I mentioned to work colleagues that I wanted the power bricks from failed equipment.  Careful with what you ask for - I now have boxes of the bricks and warts.  Sometimes the output voltage, amps, and barrel connector fit the application - a Netgear brick provides aux power to my club's TIU.

Many cell phone chargers output regulated 5v and are perfect for Miller signs.