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Old 30th March 2014, 09:13 PM   #1
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Default Harman-Kardon hk6200 repair

Hi all, I'm Javier from Argentina. I've been following many threads and I think you are a great group of people helping each other.
I need your advice. I have an hk6200 that started failing lately. While listening the muting protection disconnect the output. The it comes again for a while and stops again. It takes ages to turn on. So I thought a bad capacitor in the pritection circuit. I changed every one and the transistor that I guess senses if there is dc in the output ones. It came alive for a few minites and started failing again. There is no dc in the output transistors but there still a difference between the voltage in the base and the emitter so the collector sends voltage to the muting protector. Any ideas? I could post a pic of the circuit if that's allowed, at leas the protection part. Any help will be welcomed. Love that amp sound.
Thank you all!!!!
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Old 30th March 2014, 11:28 PM   #2
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Hi again my friends, I think I solved the problem. I worked hard checking all solders but apparently forget one in the protection circuit that senses one channel dc offset. My beloved hk6200 is now alive again. One thing to note that almos all components were free, I had to solder the whole board again. Thanks anyway.
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Old 31st March 2014, 02:28 AM   #3
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Congradulations! Your desire to repair kept you working with excellent outcome....Those type of problems can make a man crazy.....
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Old 1st April 2014, 01:03 AM   #4
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Default Bad News

Today the amp refused to turn on. I'll change a couple of transistors that I believe are not working properly. Could it be that the heat from the solder had changed temporarily their properties making them work while hot and now that they are cold they are not working again? Just guessing. Any ideas???
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Old 1st April 2014, 01:55 AM   #5
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You must resolder the connectors of the data bus from the main Blast since there are some flaws are generated by cold welding. So happened with mine. good luck
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Old 1st April 2014, 04:35 AM   #6
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If you are young, you can locate dry solder by naked eyes. If not, use eye loup/magnifier. Remember, the direction of light makes lot of difference for this purpose.

Gajanan Phadte
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Old 1st April 2014, 05:48 PM   #7
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Thank you guys!! I think I'll resolder everything trying to be more exhaustive. I'll keep you posted.
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Old 1st April 2014, 06:11 PM   #8
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Thank you guys!! I'll resolder everything from scratch. I'll keep u posted.
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Old 1st April 2014, 06:41 PM   #9
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They make solder flux pens for resoldering & touch up. They work good for this application.
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Old 5th April 2014, 11:49 PM   #10
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Hello everybody, after dealing with the amp a little mpre time I rework the whole board. However that was not the problem. I thought about one of the two transistors that senses the dc offset in each channel. I discovered that at the output resistance the voltage was zero, however ther was a difference that trigered the third transistor and the protection was activated. I removed both and found one transistor open. It was an A970. The new A970 had the pins in different order so I had to figure out the correct position. I exchanged B with C and soldered the new one. Voila. My little gem is on again. Let's cross our fingers. The replacement had a lower beta so I'll try to find a better option. Thank you all for the counseling. One last word. I made flux with rosin and isopropyl alcohol. See you next time.
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