Thank you, Ed and Brian.
On another note, having installed the decoder into the GP38-2 successfully, I went on and installed the decoders into my 2 AZL E8. One went well, the other not so well.
I slipped with my tool and scrapped off a resistor. I was able to solder it back on but something else must be damaged because the loco can move forward only.
Duh!