[arm-allstar] Help with home built Allstar node (Phil Hazelton)

[am_fm_radio at yahoo.com]

A better diagnosis would be available if you provide a schematic of your modified sound card. Is the BF888 keyed directly from a GPIO pin on the Raspberry PI or on the sound chip? Likewise is there a PTT driver transistor.. Is it open collector configuration.
What I recommend you to do is to lift the PTT line to the radio.. then watch it on an active node to see if operating properly. If you don't have a scope a LED and a resistor can be substituted to watch PTT action.
Also is the BF888 on high power? Is the BF888 antenna close by? It could be causing RF feedback and causing the PTT circuitry to remain on... That can be caused by RF getting into the BASE of the PTT transistor..  

Have you played with PTT inversion option in the SIMPLE USB-TUNE- MENU APPLICATION?