The unit does not have a LCD or other display. Yamaha use/flash the power on
lamp to communicate diagnostic information. If the amp is in protection, then
at subsequent p-on, the lamp will either flash 3,4,5 or 6 times corresponding
to Thermal/OLV, DC protect, I, PS protect respectively, see sm pg 25.
The sm also explains how to read the protection history, the information is
presented in binary form where a full power flash = 1, no illumination = 0
and dim (33%) illumination is used as a data separator. The dim, dim
sequence indicates end of field, start of next field. You basically need
to count the number of full power flashes for each field, this then corresponds
to the value of that field.
The information is formatted according to the table on page 28, ie, history
number, type of protection, speaker relay state,,,
Working through the lamp sequence beneath this table,
start
dim=start data
bright=1
dim=separator
dim= end field, start next field
Interpretation: Field 1 (History Number) has the value 1.
bright=1
dim=separator
bright=2
dim=separator
bright=3
dim=separator
bright=4
dim=separator
dim= end field, start next field
Interpretation: Field 2 (type of protection) has the value 4(PS1).
off=0
dim=separator
dim= end field, start next field
Interpretation: Field 3 (Speaker relay state) has the value 0(off).
bright=1
dim=separator
bright=2
dim=separator
dim= end field, start next field
Interpretation: Field 4 (Data upper half word/8 bits) has the value 2.
bright=1
dim=separator
bright=2
dim=separator
:
bright=15
dim=separator
dim= end field, start next field
Interpretation: Field 5 (Data lower half word/8 bits) has the value 15.
combining Data 4 and 5 results in H'2F (=47), note 15=hexadecimal "F"
bright=1
dim=separator
off=end
Interpretation: Field 6 has the value 1.