Need Help! My Class A Amp Is Running Very Hot

the cabinet over or around the vents  it is burning hot , I even feel the heat on the sides of the cabinet,

Can you measure with a thermometer?

IF it is an used unit, make sure it is a 115v model ( not a 100v Japan model ) if you are in US otherwise a transformer is needed!

How hot is too hot, how hot is burning hot?

Measure with a thermometer !

+1 @ramtubes and erik,

Plug in the L-590 to a KILLAWATT to verify if the bias as specs

Power consumption 330W
260W (under no signal)

If OP's (khmyjy) amp is L-590AX and not the AXII, there's a possibility his amp is a 100v japan model.

The L-590AX is spec’d as consuming 220 watts at idle (310 watts max). The L-590AXII is spec’d as consuming 260 watts at idle (330 watts max).

I just did another reading from the Killawatt
Standby =1.1W
Idling power on with no input =318W
With input and music playing =326W
60Hz Volt 122

I did some google search and found the following:
L-590A / L-590AII power consumption is 280 watts at idle,
L-590AX power consumption is 220 watts at idle,
L-590AXII power consumption is 260 watts at idle.

If OP’s amp is a L-590A or L-590AII, power consumption is 280 watts at idle at 115 Volt, according to calculation based on ohm’s law, the power consumption at idle at 122 Volt it should be 316 watts. So it is well within spec.

If it is a L-590AX, the power consumption at idle at 122 Volt it should be 248 watts. IMO, it should go for a check-up.

If that is a L-590AXII, the power consumption at idle at 122 Volt it should be 293 watts. Maybe it is best to ask the manufacturer if 318 watts is still within spec.

just want to be sure it’s ok since it is a preowned unit

Obviously, most amps will survive life with higher input voltages but it's not necessarily good for them, best to ask the manufacturer run at 122 Volt continuously for the L590AII is OK!