Bacta6 std codes 91 00 any thing from 90 to 9f is software. Processor card or Impact then. Its not the psu i can tell you that 1million %. Impact would display error 56-xx.
On your processor card Partno. 045251 looking at it with the edge connector to your left D2 which is more or less top right there is that D2 which is a diode ZN404 tell me what way it faces. This is for only Combined processor and memory card
Also on Impact can you tell me if poss IC U13 which is next to the Data/Serial port if pin 7 has been cut or the leg has been removed also the reset led had been removed or is fitted.
Also try and do a complete ram clear turn off machine connect your speaker back on as you will need it. Hold the test button normaly red unless your left with a yellow rubber pad whiles holding it turn the machine on.Impact will try and reset but still keep holdings you will hear a number of pops comes from the speak. Ok impact will boot on its own or after 30 secon`s take your finger off the button. Impact will try and boot you may get error 53-xx. Thats more then normal as your forcing the ram to reset and its profile.
Another thing to try is take your wire off the speaker again power it up and just let Impact timeout. Its will just stay there with the error or will boot up as normal.
error 48-xx is Tamper Alarm BTW
.._-=It`s not a problem only a challenge =-_..