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Harman Kardon 930 Short out - need help!

Yes, it runs smooth apart from the initial pop powering off or on.

I replaced the oil caps with orange drop 0.1uF 600V caps. There is a pic of the bottom side of my 930 up chain in this thread. I will check if my unit has a power switch snubber cap (spark killer) or not. If not, I'll add one. I know I have a couple of them in my stock somewhere. That's funny.....I had a 630 too as well some time ago and don't recall this issue.

Anyway . Good info Mr. Nick. Much appreciated.

Tony
 
TonyFinn said:
Yes, it runs smooth apart from the initial pop powering off or on.

I replaced the oil caps with orange drop 0.1uF 600V caps. There is a pic of the bottom side of my 930 up chain in this thread. I will check if my unit has a power switch snubber cap (spark killer) or not. If not, I'll add one. I know I have a couple of them in my stock somewhere. That's funny.....I had a 630 too as well some time ago and don't recall this issue.

Anyway . Good info Mr. Nick. Much appreciated.

Tony
Click to expand...
Hey Mr. Finn, Did you ever fix that 930? I have similar mysteries like your on mine
 
I just assumed that was the normal operation of the HK 930, so just turning off the speakers during power on or off was the protocol I used for months after, and with no issues. No DBT in the path.
I have since sold the unit, but wish I hadn't. Really nice sounding receiver. Keep in mind that I had totally recapped the unit with new electrolytic capacitors and many new modern equivalent transistors to the best of my recollection, so your issue may be different than mine despite similar conditions. I hope this helps you.
 
TonyFinn said:
I just assumed that was the normal operation of the HK 930, so just turning off the speakers during power on or off was the protocol I used for months after, and with no issues. No DBT in the path.
I have since sold the unit, but wish I hadn't. Really nice sounding receiver. Keep in mind that I had totally recapped the unit with new electrolytic capacitors and many new modern equivalent transistors to the best of my recollection, so your issue may be different than mine despite similar conditions. I hope this helps you.
Click to expand...
Thanks, This unit hasn't been recapped, but it blows the Left channel fuse so I have to dim-bulb it. unless the preamp is not connected.... just starting-out in the world of troubleshooting, although I have a bunch of test equipment, but not enough experience. I notice the manual is screwed-up as to left vs right. I am starting to figure-out how to check voltages like bias. The right channel works so I have been comparing in situ readings between channels for resistance and between transistors, and the pwr transistors seemed to check-out ok out of circuit.
I think the thump on power down is a function of caps draining, as many old amps did not have any protection built-in (like relays)
 
As you are finding out, there is a learning curve. Keep at it though, and a lot of these type threads help. If you properly checked the output transistors, and you know for sure, those are okay, i would suggest taking a look at the driver transistors ( i think there are 4 of them), and any transistor on the main amp board. I usually check board transistors in circuit, as a short can be easily identified. If you're not already familiar, there is a way to check NPN and PNP transistors using your multimeter. I recall learning from a youtube video. If your left channel is suspect because it blows the fuse, you would clearly start there. There are many AKer's on here, at least a level above me. Good luck.
 
Thank you. yes these forums are really good. I check the rails and found higher than 39 volts and the main caps are above the 6800mf rating, so I'm going to start with a recap, then check-out the voltages and transistors on that driver board.
 
@blhagstrom Do you still have some 930C parts? I'm looking for the little board that is connected to the TR905-TR906 Someone rebuilt the one I'm working on and ditched all that and just put 1 EGC186A looks pretty hacked, and I too have to power-on dim bulb nuclear option. There's no way people should have to power the unit on, wait & then engage the speaker switches. I'm trying to find-out how to fix that. (See my other posts)
 
blhagstrom said:
Don’t remember ever having a 930.
Click to expand...
Oh, I read earlier in this post, but I must have made a mistake:
"I am now hooked into the WA state recycle program and my connection cleaned out a repair shop that moved.

I am buried in junkers now and many are low life junkers.
The 930 was surprising but half stripped and the tuner was whack.
She's parts now."
Well, if you come across one or have any knowledge to impart, I'm very much appreciated.
 
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