HK 730, hiss on left channel

[omrix]

Hello!
My Harman Kardon 730, had been fully recapped about a year ago. Last week I've noticed that there is faint hiss on the left channel. The hiss is quite stable with slight popping and random cracklings. It is not influenced by the volume knob, balance knob or any other knob on the panel. It is just there, on any input of the selector... If I turn the volume enough, the music will override the hiss. Disconnected the speakers and plugged headphones, but still...

Where on the signal path would you suggest me to start looking at...? And what should I look for...?

Thanks,
Omri...

 

[Soundork]

I too would be interested in responses to this.

If I were to guess, a solid state device in the power amp section is starting to malfunction.

 

[A23gt]

Do you lose the his with headphones? If so, I would think amp section. Could the balance or tone controls cause the hiss? Would be cheaper than tearing into the power amp section.

 

[Leestereo]

If the problem persists with the pre-main jumpers removed, the problem is in the power amplifier, very likely the input differential pair (Q402, Q404) is failing. The original 2SC1400s can be replaced with a pair of hFE-matched KSC1845 transistors.

 

[ivandezande]

That thing is chock full of noisy 2SC1312's I believe that need to go. As Lee said, get a bunch of 1845's and go to town.

 

[dlucy]

That thing is chock full of noisy 2SC1312's I believe that need to go. As Lee said, get a bunch of 1845's and go to town.

Yep, 2SC1312 is a known noisy bad boy. http://www.audiokarma.org/forums/in...ilure-prone-whatever-and-replacements.731653/