Lexicon 300 freezes at startup, stuck on "Front Panel Code Version 2.01"!

[Bjorn Andersson]

A customer brought me this Lexicon 300 with this startup problem.
Have checked all the voltages according to the service manual for the Lexicon 300.

+5V (+4,96V), +12V (+12,38V), -12V (-11,95V), +15V (+14,78V), -15V (-14,90V),
+5VA (+4,93V), -5VA (-4,98V), all voltages measured inside parentheses.

Battery checks out at +3,12V

Tried the RED reset button on the host board, no luck...

Have cleaned and grounded all pin on the U21 RAM chip but the 300 freezes on the
"Front Panel Code Version 2.01" in the display.
Sometimes this clear the problem according to a freeze problem in the 300.

Cleaned all the pins on the EPROM´S and reseated, but no luck.



Do we have any Lexicon experts out there who can point me in the right direction? ;-)
Any help or tips what to look for would be highly appreciated!

 

[radardoug]

Could be a faulty code eprom? Can you scope the address lines of the processor, and see if it is still running, and what address it is at?