Job Number

0010-02

Equipment type

Home synthesiser

Maker + Model #

Yamaha PSR ?400?

Made in

Japan

BAD

1

Keys C0, F#0, C1 do not produce sound when pressed

GOOD

1

Powers up

2

Good sound output

3

Rest of and panel controls work good

Repair summary

OPEN TRACK IN KEYBOARD MATRIX

Full repair description and observations

1

When the synth was opened, there was a set of diodes on a separate PCB strip over the keyboard section “keyboard matrix”

2

All the diodes had a steady 5V, except 3, which gave a fluctuating voltage and also did correspond with the respective faulty keys

3

The keyboard matrix was opened and after some inspection an open track was observed. The track, which was corroded, supplied 5V on the 3 faulty keys

4

The track was joined by a solid core wire and the keys now worked perfectly