My infrared thermometer measures the BHK heat sinks as high as 123 degrees.
Is that in the range of normalcy?
It would be advisable to put the temperature reading in context, is that at idle (unlikely) or after playing what type of music (acoustic, orchestral/Beethoven, Dvorak, Handel - best to say what was playing, Rock music) at what level(loud, soft but preferably measure Db level @1m) after how long and into what speakers with what impedance rating?. This would help answer your question.
As a start I would suggest measuring the temperature at idle, connected to the speakers. Then a 2nd measurement after playing one type of music for about an hour with above observations.
I haven’t used my IR thermometer on them, but my fingers (very uncalibrated) can agree those temps are on my cooling fins after a few hours, also.
This temperature strikes me as normal.
If you can, try to have at least 2.5" or more space above the amplifier to give better air circulation. I don’t remember what my temperatures were, but increasing the space above the amplifier brought them down a few degrees.
If it is in Fahrenheit then yes, it is perfectly normal. The fins are slightly hot to the touch.
Have no idea what the “normal” temperature is supposed to be. I do know there is a safety circuit that shuts the amplifier off if it overheats. It’s very effective. I had a large party at my house this summer to celebrate my oldest daughter’s engagement. Lots of folks, drinking and dancing. At the end of the night, the stereo was cranking. I was even running a battery powered fan over the amp (not very well placed) and it shut down in the middle of a song. Freaked me out at first: party stopped dead in its tracks. The power button was flashing rapidly. I stayed calm, shut down the amp and let it sit for a minute. Turned down the volume on the pre-amp and fired the amp back up: back in party mode. Just not quite as loud. No harm, no foul.
My BHK250 also runs quite warm, but not hot. By comparison, my dual McIntosh MC275 tube amps could heat a small room. For the Macs, and now the BHK250, I’ve been using two silent mini-fans that connect to a dual USB plug connected to a corded lamp switch. This arrangement allows me to operate the fans remotely. The fans are placed behind the BHK and flank the heat sinks. As a result, the sinks have merely a gentle warm feel. The fans, dual USB plug and remote lamp cord are all available on Amazon for a total investment of about $40. The caveat is to get “silent” fans, of which some are more so than others. My fans are not totally silent, but don’t intrude on the sonic performance. The amp cooling gives me peace of mind, though as mentioned, it doesn’t run hot without the fans.