Here is a fairly easy install in a BLI refurbished HO EMD F7 that came DC only. The set cost $100.00 total. I purchased the decoders, 678-828040 and 28mm speakers from Litchfield. Free shipping. Good prices. I use Scotch Indoor/Outdoor mounting tape with Red backing , part number 4353. on the styrene shelf to mount the decoder.
Below is what my F3 looks like in the A unit. This is next for my F7.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I just finished up the light board for this F7. I used the 3mm Golden White from Litchfield. I use the 680 ohm resistors. The two LED's for the number boards are in series with one 680 ohm resistor.
The single LED that is standing on the PC board lights up the cab but goes out as soon as speed step one is selected. The inside of the loco is the same as the PCM F3 set.
With the F7 and F3 in ABBA, there is almost five lbs of loco. They sure can pull.