I have a Lexicon MPX-1 that is dying on boot up.
When first powered on, all the LEDS light up and then it begins the boot process where the peak LEDS start to count up. It gets to the place in the boot process where the main display should come up but the display remains blank and none of the LEDs are lit.
I have the service manual and schematics and have been looking into what may be the issue.
I tried the entering the extended diagnostics but the unit just starts going through the boot process and then dies.
I also tried the emergency diagnostics and was able to select the "Initialize Operating System" but when I execute it again the unit just goes blank. Not sure what the LCD Write/Read Scope loops are as the manual does not explain their use.
I did some initial trouble shooting using the service manual and all the voltages are within tolerance, all the clocks are also good and within tolerance and the battery is at 3v.
Looking at the reset lines, it looks like the unit is hanging right after the reset line for the Lexichip goes high (unreset). It appears that this is where it is hanging up. It never gets past this point so the DSP reset line is staying set (low).
Looking at signals on the scope I can see that there are reads happening between the Z80 processor and the Lexichip.
At this point I am not sure what the issue could be as I am not sure exactly what self test is running. Possibly the Lexichip itself or perhaps its associated the DRAM.
Has anyone run into a similar issue and if so could provide any points on where to look?
Any help would be most appreciated.
Thanks, Dan
OK so after a lot of trouble shooting the issue is a bad EPROM. The checksum is not passing.
Unfortunately I dont have an image to burn a new one. I am trying to get one from Lexicon/Harmon but it is not looking good.
I also can not find either a programmed EPROM or firmware image one on the web anywhere.
Anyone have an image for the ver 1.1 firmware or a EPROM that I could acquire?
Any help would be much appreciated.
When first powered on, all the LEDS light up and then it begins the boot process where the peak LEDS start to count up. It gets to the place in the boot process where the main display should come up but the display remains blank and none of the LEDs are lit.
I have the service manual and schematics and have been looking into what may be the issue.
I tried the entering the extended diagnostics but the unit just starts going through the boot process and then dies.
I also tried the emergency diagnostics and was able to select the "Initialize Operating System" but when I execute it again the unit just goes blank. Not sure what the LCD Write/Read Scope loops are as the manual does not explain their use.
I did some initial trouble shooting using the service manual and all the voltages are within tolerance, all the clocks are also good and within tolerance and the battery is at 3v.
Looking at the reset lines, it looks like the unit is hanging right after the reset line for the Lexichip goes high (unreset). It appears that this is where it is hanging up. It never gets past this point so the DSP reset line is staying set (low).
Looking at signals on the scope I can see that there are reads happening between the Z80 processor and the Lexichip.
At this point I am not sure what the issue could be as I am not sure exactly what self test is running. Possibly the Lexichip itself or perhaps its associated the DRAM.
Has anyone run into a similar issue and if so could provide any points on where to look?
Any help would be most appreciated.
Thanks, Dan
OK so after a lot of trouble shooting the issue is a bad EPROM. The checksum is not passing.
Unfortunately I dont have an image to burn a new one. I am trying to get one from Lexicon/Harmon but it is not looking good.
I also can not find either a programmed EPROM or firmware image one on the web anywhere.
Anyone have an image for the ver 1.1 firmware or a EPROM that I could acquire?
Any help would be much appreciated.
