I checked the PC boards for a 4-6-0 and 4-4-0 locomotives since there has been questions in the past.
The 4-6-0 PC board the decoder is plugged into has 1,770 ohms resistance in series with the plus lead, blue wire, for the LED. There is a diode in the minus lead, white wire, that drops the voltage by .7 volts. Good reason for dim lights when plugging a decoder into the PC board.
If you hard wire a decoder, a 1,000 ohm resistor is sufficient. I have done that with a Spectrum 4-4-0 and a Spectrum 4-6-0.
The Spectrum 4-4-0 PC board has 1,424 ohms in series with the blue lead and a diode in series with the white lead.
I suspect the PC board for the 2-8-0 must be about the sames.
Rich