Trying to repair a Harmon Kardon 590i

[El-Barbaro]

Hey everyone, lately I've been having issues with one speaker overheating and I'm worried it might be an issue with my receiver. I have a budget set up of a Fluance turn table which is connected to a Harmon Kardon 590i and c100 Energy speakers.

The issue started yesterday when my left speaker started putting out with funky smell and was hot to the touch. So I opened up my receiver but I couldn't make heads or tails of it. So I switched the speaker connections and then my right speaker started giving me the same issue. I'm trying to fix this myself instead of buying a new receiver or amp, but I don't really know where to start. I know it's not my speakers and all I can really come up with is my Harmon putting out a "bad signal" can anyone give me some advice on what I can do?

 

[mbz]

Measure dc voltage at speaker posts of problematic channel, should be less than 50mV dc.
Volume set to minimum, no source "playing". Try with speakers disconnected (cap coupled?)
Download the services manual and service bulletines from hifiengine, need to register to
prove that your not a robot, it's safe/no spam...

 

[Binkman]

Welcome to AK! DIY asylum.
service manual and service bulletins listed may apply.
--------------------------

my left speaker started putting out with funky smell and was hot to the touch.

NOT good... most likely damaged so don't play it.

 

[El-Barbaro]

Welcome to AK! DIY asylum.
service manual and service bulletins listed may apply.
--------------------------

NOT good... most likely damaged so don't play it.

Don't play the speaker or the receiver? I think the speakers are fine, i switched which inputs they were connected to and then the right one started heating up. But I'm trying to figure out a starting point on fixing it, like I can't really understand why it's throwing out too much power to the point where it's over heating my speakers.

 

[El-Barbaro]

Measure dc voltage at speaker posts of problematic channel, should be less than 50mV dc.
Volume set to minimum, no source "playing". Try with speakers disconnected (cap coupled?)
Download the services manual and service bulletines from hifiengine, need to register to
prove that your not a robot, it's safe/no spam...

Ok, I'll get a voltmeter this weekend and figure it out.. so two things then; if it's higher than 50 what does that mean,

Also, what is cap coupled....?

 

[Binkman]

I can't really understand why it's throwing out too much power to the point where it's over heating my speakers.

Too much DC current.. speakers are AC. We measure DC offset to determine excessive DC current in mv... (millivolts) on the DMM (digital multi-meter.. measures, ohms, dc, ac and some meters have diode check..

 

[mbz]

if it's higher than 50 what does that mean

ideally, DC off set should be 0mv, but 0-10mV is excellent, under 20mV also good, 50mV tolerable and 100mV
is starting to get high. From your symptoms the off set would need to be volts not mV.

what is cap coupled....?

Others can provide a better explaination but in a nutshell it's a particular amp design that has
a moderately large (2200-4700uf) cap at the output of each power amp stage. Speakers or a load
needs to be connected to load the cap so it blocks the large (20-40Vdc?) dc voltage at the power
amp. Testing such amps with no load connected can give alarmingly high results.

Would be best to puchase some high wattage 8-10ohm load resistors rather than smoking speakers
Higher the watts the better, at least 10W but 50W better if not too expensive.

 

[MyLastWord]

Probably not related to the OP issue but just want to chime my recent experience with HK590i. Mine was with the control/display issue, i.e. no indicator what-so-ever. Took me a long time to trace back to a single fusible resistor went bad.
Replaced with a 1% metallic resistor and everything was good. I read somewhere state that fusible resistor drifted/opened/shorted over the time easily. May be some fusible resistors around Power supply/Power Amp to check.

 

[CouchPotato]

Hello, not trying to hijack the thread but I have the same issue with the same HK 590I receiver. I followed the dummy load suggestion from @mbz and have a right channel reading of 29.1v and a left channel reading of .464v. After a minute or two the 8ohm 120watt dummy load got pretty hot on the right channel. The receiver fried one of my Nova 6 speakers resistors and melted the crossover plastic under it. Would I be better off opening a new thread ? I sure need help on what direction to go from here.
Thank you

 

[CouchPotato]

I'll create a new thread and post pics of the issue.
Thanks,