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Harman Kardon 730 Twin Issue

G

gloitz

New Member
Hello, I recently bought a 730 twin, and it has this issue where when connected to speakers, it makes a sort of popping sound and then hum. No audio from either channel. I took it to a tech, and they said something about the bias being changed, and not being able to fix it, and ultimately they returned it to me without fixing the problem. I decided to take a look inside, just out of curiosity and it looks like these might be modern parts and not original to the receiver? I don't know too much about the inner workings of stereo equipment, but I would really like to be able to get this one working. Any ideas or suggestions would be greatly appreciated.IMG_9904.jpgIMG_9904.jpg
 
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That trimmer and cap are not original. As for the tech who wouldn't work on it...hmmm. He must be booked out for a quite a while to turn down a job like this. These are pretty easy to work on. The amp board unplugs so you can work on it right on the bench. Where are you located? If you are in the US, I'll bet there's an AKer close by willing to lend you a hand.
 
I'm in California. The guy I took it to didn't really seem like he was putting any effort into it. I called him after about a month and inquired about the status of it, and he said that he couldn't find the schematic for it. It took me all of about 30 seconds to google it and find it, downloadable and everything for free. Another month went by and i inquired again, and he just said it had something to do with the biasing, I didn't really understand everything he told me. Would replacing those two parts just involved de soldering them off the board, and putting appropriate ones on?
 
The only thing that might not be appropriate with either the cap or the trim pot would be if they were the wrong spec. There's nothing wrong with their quality. (They're equal to or better than what was in there originally.)

Has the problem existed since you bought the unit or did it work correctly then fail?
 
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