Got_Horns Posted February 14, 2023 Share Posted February 14, 2023 Just picked one up as a package deal. Left channel doesn't work. Probably needs a good going over. I have some deoxit, screwdrivers, soldering iron and the interwebs....what would be a good resource on how to fix this thing? Thanks 🙏 Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 17, 2023 Share Posted February 17, 2023 On 2/14/2023 at 2:10 AM, Got_Horns said: what would be a good resource on how to fix this thing? Significant experience. 1 Quote Link to comment Share on other sites More sharing options...
OO1 Posted February 17, 2023 Share Posted February 17, 2023 On 2/14/2023 at 2:10 AM, Got_Horns said: .what would be a good resource on how to fix this thing? Thanks 🙏 the Service Manual as the 1st step 2nd would be the troubleshooting 1 Quote Link to comment Share on other sites More sharing options...
Got_Horns Posted February 18, 2023 Author Share Posted February 18, 2023 22 hours ago, John Warren said: Significant experience. This is what I'm working on. I'm ignorant but not scared. The good thing about this HK? it was practically free. So if I muk it up, I don't care. If I get it working? it should be a nice sounding unit. Quote Link to comment Share on other sites More sharing options...
henry4841 Posted February 18, 2023 Share Posted February 18, 2023 3 hours ago, Got_Horns said: This is what I'm working on. I'm ignorant but not scared. The good thing about this HK? it was practically free. So if I muk it up, I don't care. If I get it working? it should be a nice sounding unit. Do you have a basic knowledge of electronics? Even very knowledgeable electronic gurus are not the best diagnostic experts. Many technicians are parts changers, much like mechanics that work on your car, instead of a good electronic repair technician. Most of the time one can expect output transistors along with driver transistors to have failed with one dead channel. Of course there are many other causes as well. Many youtube videos on how to test them in circuit or better yet with a transistor tester out of circuit. Quick but not definitive test is to check each pin with an ohmmeter to ground. Would show a shorted lead to ground. BJT transistors are basically two diodes in one package. Below is good place to start. https://www.hifiengine.com/manual_library/harman-kardon/avr135.shtml Looking at the schematic I would not touch it and I restore and repair old audio equipment as a hobby. The reason is most newer receivers use chips instead of discrete transistors like most made in the 70's. Virtually unobtainable aftermarket. Hard enough to get discrete parts for repair these days. Sorry for rambling but I was checking out the schematic while typing. Quote Link to comment Share on other sites More sharing options...
Got_Horns Posted February 18, 2023 Author Share Posted February 18, 2023 25 minutes ago, henry4841 said: Do you have a basic knowledge of electronics? Even very knowledgeable electronic gurus are not the best diagnostic experts. Many technicians are parts changers, much like mechanics that work on your car, instead of a good electronic repair technician. Most of the time one can expect output transistors along with driver transistors to have failed with one dead channel. Of course there are many other causes as well. Many youtube videos on how to test them in circuit or better yet with a transistor tester out of circuit. Quick but not definitive test is to check each pin with an ohmmeter to ground. Would show a shorted lead to ground. BJT transistors are basically two diodes in one package. Below is good place to start. https://www.hifiengine.com/manual_library/harman-kardon/avr135.shtml Looking at the schematic I would not touch it and I restore and repair old audio equipment as a hobby. The reason is most newer receivers use chips instead of discrete transistors like most made in the 70's. Virtually unobtainable aftermarket. Hard enough to get discrete parts for repair these days. Sorry for rambling but I was checking out this schematic while typing. So it's trash? Dang, it was a reason I did the deal. I thought it was an older vintage. Dark blurry picture... Quote Link to comment Share on other sites More sharing options...
henry4841 Posted February 18, 2023 Share Posted February 18, 2023 46 minutes ago, Got_Horns said: So it's trash? Dang, it was a reason I did the deal. I thought it was an older vintage. Dark blurry picture... Pretty much when it cost more to fix than worth. Not many repair techs left in this throw away world . Television techs are pretty much the thing of the past. When I worked at a copy machine co. the techs do not repair boards but rather replace the entire board with a refurb or new one. Parts changers. Sorry to be a bearer of bad news but a quick look at schematic tells the story. 1 Quote Link to comment Share on other sites More sharing options...
billybob Posted February 18, 2023 Share Posted February 18, 2023 On 2/14/2023 at 2:10 AM, Got_Horns said: Just picked one up as a package deal. Left channel doesn't work. Probably needs a good going over. I have some deoxit, screwdrivers, soldering iron and the interwebs....what would be a good resource on how to fix this thing? Thanks 🙏 At least do the factory reset. With a simple receiver would check the balance first. There is troubleshooting online but after the basics, would consider it not cost effective to fix. Can buy other H/K for inexpensive. Careful with the high voltage. 1 Quote Link to comment Share on other sites More sharing options...
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