Ik had toch even een mailtje naar Hammond gestuurd over de warm aanlopende PT. Dit is wat ik terug kreeg.

Good afternoon Karst-Erik

Thank you for your email.

I have spoken to our technical team and they have advised the following.
The calculated temperature rise of this part at continuous full load is 45 C degrees above ambient ( room temp ) . The total temperature at 25 C room would be 70 C . The surface temperature would be close to 65 C which is hot to touch by hand. This is normal.

The material used to build this part is Class B ( 130 C ) so there is a significant safety margin at full load.

The losses are: Core = 8.12 watts , which are always present when turned on ( power to input ) . The copper losses are 18 watts which are dependent on the
loading , music level etc.

The core size was held similar to the 60 Hz model in order to fit same mounting location but use a high grade of lamination to keep core losses due to 50Hz
models lower .

I believe the unit is working as expected. Hope this helps explain .