Boss ME50 multi effects pedal

[N_Cook]

All LED flash on &off then latches up with the seven segment display
showing the decimal point only. Removed the single board from chassis
No stuck sw, no bad solder joints seen, no bad ESR caps. One time only,
pressing on area of pins 1 to 20 of 144 pin Boss chip the board started
responding to switch pushes, not repeatable since. Any special incantation
known ?

 

[N_Cook]

It will read data from the EEPROM always, so can read version number and
factory reset. Sometimes it will function, responding to switch pushes, from
switch on. At least a full service manual with all data lines etc is on e-S.
All datalines between DRAM and uC have continuity, in area where there sems
to be pressure sensitiviyt. Now to power up and check some DCs