Harman Kardon HK6600 - hum and pops in the speakers on powering

Hello guys,

I think that this is my first post here on diyAudio, so first I would like to say hello to all ladies and gentleman here

Just received my amp, and it is really in mint state... not a single scratch even under close inspection and upon opening the cover I have seen the well known "millennium spider net" inside... long time not used amp

But it suffers from strange issue I haven't seen until now... after powering on, there is some period of up to 15 seconds seconds when it is quiet (O know that HK use muting circuit), but when amp starts, the loud single pop (bang) came from the speakers (like champagne opening) and it is loud even the volume is at 0 and then some sort of irregular noise, more like hum can be hear for some time; approximately 15-30 seconds. After that everything is OK and it plays very nice. If I turn it off and on immediately I don't hear this. If I turn of for some short time it happens again. The speakers switch when switching from A to B and A+B or back produce the same champagne opening sound at every position change, but tape monitor switch can produce some noise as well. So it could be the switch issue, but why then this occurs just after turning on the amp and after some short period it stops... or maybe I don't hear this while playing the music 😕😕

Anybody have had similar issue or experience with HK?

Any help is welcome

Thanks,
Nikola
 
Sounds like a high resistance soldered joint when left on heat completes the circuit .


If it was a mechanical switch issue ( high resistance contacts ) then moving the switches on and off ( while unplugged ) should rub off the deposits or use switch cleaner ( carefully!! ) .


A high resistance disconnection in a soldered component can take a while to trace but for the non technical person use an insulated prod to --LIGHTLY -- push the circuit board up and down to see if that makes it better or worse.