Troubleshooting occasional popping from solid state amp?

Trouble, shooting and occasional popping are becoming an all too frequency occurrence in today’s society. 

I picked up a ‘90’s era old HARMON KARDON integrated amp and tuner locally on the Uber-cheap Craigslist- type ad with a view to refresh them and pass on to a senior citizen transitioning into a retirement home.

initially they were working fine for me for a couple of weeks, but then the amp suddenly developed the intermittent occasional popping and subtle cracklings noise. I popped the cover , but other than the usual dust from an old unit , I could not see any obvious issue to the untrained eye.

i ignored them initially while I assessed next steps forward, until there was suddenly a louder sequence. Now my antenna was raised to the point that I took it in to a local professional tech for a necessary look-over.

Good thing I did to avoid a potential FUHBAR in the making.
The tech popped open the box and identified a power supply failing section that was causing an intermittent electrical arcing ...ergo, a hazardous fire hazard in the making. I didn’t see it when I first popped open the cover before taking it in . He said it was an age-related failure typical of old units.
A $150 comparatively cheap cost-of-insurance fix IMO. Be careful out there.

Hi,
 First disconnect everything and try to identify if this popping is coming only from the amp. Cold joints are not always easy to trace and you have to dismantle the unit to check thoroughly but normally they keep the unit working or not. 
A 20 year old product needs some attention if you want to keep it.
Pops like that are sudden short bursts in the circuit. Better checked.

Open up amp on bench. Connect to small test speaker. Power up. Use insulator like thin dry wooden rod to push on board and connections until faulty joint is found. Use freezer spray too. Look for leaky electrolytic capacitors. Consider replacing them.