I recently acquired an early 80s HK PM660 int. amp.
It seems to be a low-hours unit and is very good cond, with almost no cracked solder joints.
The four 10,000 uF mains rect. caps are still in excellent cont, holding that value and with very low ESR.
A few other "TK" brand electro caps are down by 10 to 20uF from, say, 220uF, but the EST is still very good. I will replace them.

The main "issue", if even it is an issue, is that after the idle bias is set to 50mv both L/R channels (and DC offset is "zero'd" out), the amp will draw about 83W at the 120VAC mains (I use a KillaWatt for measuring ). This seem a bit high.
I don't hear distortion. Just clean sound. And the IDLE bias current and DC offset will slowly settle to proper values after about 20min warming. So nothing unusual about settling time.
But whole amp is running on the warm side, even though it is not class-A biased. You can take a look at the Serv Manl and maybe tell me how much idle power might be "normal." Maybe the SM idle current adj. is too high?? I can get the power draw to, say, 75W by reducing the bias current pots to 35mV per ch. Or is there another way to reduce pwr draw? I have not removed any trans. to re-apply thermal compound. So that might be an option. Or maybe adding bypass caps across more pwr regs.

I will do some comprehensive dummy load experiments soon using proper test tones (via sig gen) and o'scope. I will also run my FLIR on various heat generators, which are not just the 8 pwr trans. but also driver trans and To220 trans for voltage reg (and those heat sinks also run on the warm side).

Refs:
(note: as usual with amps and specs, IDLE pwr at 120vac is never given!!! Only max pwr draw if the amp is driving with full rated 80/ch : 328W)
SM:
https://www.audioservicemanuals.com...rdon-pm-660/11068589-harman-kardon-pm-660-amp

OM:
https://www.audioservicemanuals.com...0/11068591-harman-kardon-pm-660-owners-manual

 

The idle power will depend on the mains voltage and the transformer, and will increase enormously between 100V AC and 120V AC due to the shape of the BH curve of the transformer. So unless you have your mains voltage tightly regulated, the power taken by the transformer won't be a sensible parameter to specify.

 

The idle power will depend on the mains voltage and the transformer, and will increase enormously between 100V AC and 120V AC due to the shape of the BH curve of the transformer. So unless you have your mains voltage tightly regulated, the power taken by the transformer won't be a sensible parameter to specify.

Not sure what you're saying? I am measuring the power draw at the mains AC power plug. The power being drawn is the amp topology itself, not transformer which ALWAYS runs cool, as do the two bridge rect diode units.
IAC, I do use a Variac in experiments. The mains pwr draw does not differ much between 100 and 120. 120 is my local line voltage. And the HKPM660, which BTW is an 80w/ch amp, is designed for USA/Canada 120VAC.

 

First of all, if the amplifier uses over 80W of power, then its output transistors have to get really hot. Keep the amplifier on for an hour and touch the heatsinks with your hand. Are they very hot?
If they're not too hot, it's likely that the Killawatt meter is showing incorrectly .Connect some reactive load to the Killawatt meter and you’ll see if it shows the ACTIVE power correctly .A good load would be a high-power non-loaded transformer or a big capacitor

 

First of all, if the amplifier uses over 80W of power, then its output transistors have to get really hot. Keep the amplifier on for an hour and touch the heatsinks with your hand. Are they very hot?

Uh ... you are not addressing the issue. Look at the OP and title. HINT: "Idle".
Again ... someone ... anyone .... the SM has the topology ... so speculate how much IDLE pwr the PM660 might consume, in normal operation, powered on for say a few hours, like in an audio showroom, but not playing music.

Trevor's Bench YouTube Channel measures about 65W for a mostly functioning PM660 here: