"DA" is submodel that I was looking for. In that model (any through GA) the timing of speeds 1,2,3, and FW is controlled by Card 1, as is both the traction and PTO RTN functions. In the HA, there is limited timing function, and the RTN is handled by a relay. Is the PTO RTN working correctly (you'd have to get off the seat, the brake switch has no effect on the PTO)? Since you mentioned that the Card 1 was recently replaced, I would start by checking to make sure all the wires are on the correct terminals. Assuming all is right there, try removing the wire from terminal 6 and attempt to run the motor. If the motor runs, then there is a problem with the RTN circuit on the card.
If it does not run, the problem is elsewhere and not in Card 1. I would then use a multimeter to verify that wire 6 has voltage only when the speed controller is in the 'neutral' position, and that the voltage goes away when you advance the speed controller away from neutral (in either direction). If it doesn't function this way, then you'll have to check on the speed controller and the associated wiring. Either the START switch has failed so that it provides power on the normally closed circuit at all times [unlikely], someone goofed up the wiring when replacing switches [very possible], or someone didn't have the right switch (SPDT) and made a SPST switch work by just hooking wire 28 to power all the time [also very possible].
A good guide to have on hand, besides the HSM, is the "Simplified Troubleshooting Manual". You can get a copy from the other forum or from http://www.myelec-traks.com/Publications.html
. It will show you the voltages you should have on the various wires with the speed controller in different positions and have the brake and seat switches in different configurations.
The timing of my E15AA speed transitions seem painfully slow compared to my E20, which basically goes in real time as you press the pedal down. I'll try to get a sense of the timing on my E15 and let you know what I find. From memory, it seems like they run between 1 and 2 seconds per transition.
Let me know what you find out!