Problem with my Harman Kardon 930 receiver

sushimaster · 4th April 2010, 10:27 PM

Everytime I turn on/off my vintage Harman Kardon 930 receiver, my woofers on my speakers "pushes out and then gets sucked back in." Almost violently.

I have tried different speakers with the same results.

Does anyone know what likely could be the problem?

- Sushimaster

SoNic_real_one · 10:56 PM

Some of the capacitors in the final power stage dried out. You should replace all of them. Start with C603, 604 (623, 624 on the other channel).
Also the ones in the power supply might be of lowered capacity - replace them too.

sushimaster · 5th April 2010, 03:42 AM

Thank you very much. All the capacitors are still original, so that makes perfect sense!

- Sushimaster

latala · 5th April 2010, 12:06 PM

I have 20 or so different models of HK receivers Among them a few 930,s I am sorry to tell you this has always been a problem with this range
I have always switched off the loudspeakers using the spk switches to avoid switch on /off thumps
There are no time delay relays to do this for you The amplifier is always going to thump as it is inherent in the design remember it nearly 40 years old having said that its still a good sounding piece of kit
regards Trev

thetube0a3 · 5th April 2010, 12:19 PM

I assume yours is doing what one of the HK 4ch receivers I had did. It would push the woofers all the way out and hold them there for a bit. And then pull them all the way in for a bit, literally seconds for each.

I don't remember the 930 I had doing this. Nor can I accept its normal as there seemed to be A LOT of power there. It wasnt the typical power on thump.

I never fixed the HK I had that did it so I have to assume sonic_real_one is right.

The tone controls also seemed to move the woofers in\out if you spun the knobs back and forth.

latala · 5th April 2010, 01:47 PM

Change all the caps you want it will stilll switch on with a large thump its to do with the vas stage having a resistor and bootstrap There is no way to keep this topology and not then use a relay timer if you want to avoid the thump I used to selll these when they were brand new ! I always instructed my customers to use the spk switches
The amount the spk cone moves is effected by the cabinet loading infinite baffles were not so badly affected as say a bass reflex due to the spring effect of the trapped air
regards Trev

thetube0a3 · 5th April 2010, 03:29 PM

Hmm.
latala may be right.

Altho due to age i'd personally still replace all of the alum electrolytics. All should be cheap except for the filter cans. Those you may want to check and just leave if working good.

If this is normal which unfortunately it may very well be, you may want to simply turn the speakers off via the speaker switch before turning the 930 on and off. When you turn the receiver on simply wait 5-6 seconds before turning the speakers on. This is exactly what a timed protection circuit typically does.

I'd also check to see what kind of DC you have on the speaker terminals after the receiver has been on for a few minutes just to be safe.

4th April 2010, 10:27 PM	#1
sushimaster diyAudio Member Join Date: Apr 2010	Problem with my Harman Kardon 930 receiver Everytime I turn on/off my vintage Harman Kardon 930 receiver, my woofers on my speakers "pushes out and then gets sucked back in." Almost violently. I have tried different speakers with the same results. Does anyone know what likely could be the problem? - Sushimaster

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5th April 2010, 03:42 AM	#3
sushimaster diyAudio Member Join Date: Apr 2010	Thank you very much. All the capacitors are still original, so that makes perfect sense! - Sushimaster

5th April 2010, 12:06 PM	#4
latala diyAudio Member Join Date: Feb 2006 Location: staffordshire	I have 20 or so different models of HK receivers Among them a few 930,s I am sorry to tell you this has always been a problem with this range I have always switched off the loudspeakers using the spk switches to avoid switch on /off thumps There are no time delay relays to do this for you The amplifier is always going to thump as it is inherent in the design remember it nearly 40 years old having said that its still a good sounding piece of kit regards Trev

5th April 2010, 12:19 PM	#5
thetube0a3 diyAudio Member Join Date: May 2008	I assume yours is doing what one of the HK 4ch receivers I had did. It would push the woofers all the way out and hold them there for a bit. And then pull them all the way in for a bit, literally seconds for each. I don't remember the 930 I had doing this. Nor can I accept its normal as there seemed to be A LOT of power there. It wasnt the typical power on thump. I never fixed the HK I had that did it so I have to assume sonic_real_one is right. The tone controls also seemed to move the woofers in\out if you spun the knobs back and forth.

5th April 2010, 01:47 PM	#6
latala diyAudio Member Join Date: Feb 2006 Location: staffordshire	Change all the caps you want it will stilll switch on with a large thump its to do with the vas stage having a resistor and bootstrap There is no way to keep this topology and not then use a relay timer if you want to avoid the thump I used to selll these when they were brand new ! I always instructed my customers to use the spk switches The amount the spk cone moves is effected by the cabinet loading infinite baffles were not so badly affected as say a bass reflex due to the spring effect of the trapped air regards Trev

5th April 2010, 03:29 PM	#7
thetube0a3 diyAudio Member Join Date: May 2008	Hmm. latala may be right. Altho due to age i'd personally still replace all of the alum electrolytics. All should be cheap except for the filter cans. Those you may want to check and just leave if working good. If this is normal which unfortunately it may very well be, you may want to simply turn the speakers off via the speaker switch before turning the 930 on and off. When you turn the receiver on simply wait 5-6 seconds before turning the speakers on. This is exactly what a timed protection circuit typically does. I'd also check to see what kind of DC you have on the speaker terminals after the receiver has been on for a few minutes just to be safe.

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