If possible give the full name of the equipment and the approx year , include a brief description as well.
We may be able to locate a circuit diagram and take it from there.
Nowadays there are lots of circuit boards made with unmarked components to prevent you repairing the gear so forcing you to buy new. Though sometimes they are inked out instead of being abraided off ,so have a magnifying glass examination look in some good strong light on both sides of the PT
Quite often though on the metal heat sink bit you may find some imprinted numbers /code marks, so carefully check it out both sides .. also give any numbers found on the board ..several macro pictures from different angles and from both sides would / could be helpful.