I'm beginning to do more research and think I've found my answer:
" If you have read other reviews about the GX505 then you would know that this amp gets extremely hot to the point it hurts to touch it."
"The only issue that I noticed with it was that it did run really hot - I won't go so far as to say you could actually cook food on it, but it was uncomfortably warm to the touch after about a half hour or so of low volume listening."
"I would be cautious of buying a used GX505 because of the overheating problem"
"Technics designed most receivers (including the SA-GX series) with a fan that is programmed to run only when the volume reaches around 50-60% of the maximum output. Despite the fact that the units all have beefy static cooler fins dissipating heat from the power hungry amplifiers transistors, if you are listening the unit at lower volumes, you won't see the fan active meaning that the unit will get very, very hot. After about 1 hour running at 20-25% volume, the unit can easily get so hot that you can't touch its top surface - especially on the top left corner near the VFD display. A common issue with these units is that the VFD display can become dim due to solder joint cracks due to the heating/cooling cycle. Thus, if you want to use the unit for prolonged time (over 30-40min at a time), avoid the risk of solder cracks, components fatigue, etc - you need to modify the standard stock fan.