I suspect the problem is in part the fact that the PA-135 was wound for a 117 vac primary. Wih a line voltage of 120 vac plus the secondary high voltages will be approximately 11 volts higher.
Looking back at my original test notes on the MK IV amplifier...The secondary voltages I measured were about 13 to 15 volts higher on the high voltage secondary's under no load. This was measured on an original Dynaco MK IV amplifier.I tested several samples which confirmed these measurements to be accurate. Appears the
published specs conflict with the actual voltage measurements.I still use these MKIV amps and have not had any major issues other than the power transformer gets quite hot.
We redesigned our Dynakit Replacement PA-135 power transformer to operate at 120 vac while retaining the the original published secondary voltages within 1-2%.
I would suggest adding a CL-90 Thermistor on the AC (120) vac primary side which should reduce your voltage by about 3 volts. This will bring the voltage down closer
to the original 117 vac spec. Another option would be to use a variac which will allow you to dial in the voltage exactly.
A third option would be to contact Sal Brisindi...He is a member of this forum. Sal has a neat plug-in soft start with a voltage reducing transformer. Send me an email
and I will provide you will Sal's contact information.