KR-9600 Restoration Info
- Thread starter hopjohn
- Start date
Welcome to AK Gabe! You should introduce yourself on the proper AK forum, which is at http://audiokarma.org/forums/index.php?forums/introductions.145/
Sorry to post here I’m just new to this site but so far I love it and appreciate all the input from you guys. I have recently completed restoration on my 9600, I did all the mods and upgrades mentioned in this forum.
I did power supply B mod
Tuner mod, power supply A, also went and added an aluminum cased resistor to r-18 because I noticed it was getting hot and it had damaged the original c12 , I actually just used the aluminum case of a spare resistor I had bought for power supply B
Triac
Power amp
Led
Replace main filter caps with the obsolete Panasonics mentioned here that I found on eBay
And did a full recap on this massive amp. Nichicon gold, Nichicon muse, Elna silmic II,Wilma filmc, Ana some power series capacitors.
I don’t know if I’m forgetting to mention other things I did. Anyways my father purchased this amp back in 79-80 from a Canadian friend and I remember him enjoying this beauty until I graduated from high school in 2002. Last year I ask my dad about his old kenwood and he told me it had stopped working 10 years ago. So I went to his place picked up went through it and noticed power supply b was extremely burned and guessed that was the fault. So I went online and found videos on YouTube that lead me to this forum and sure enough I replaced those burned out resistors and this beast came back to life. It sounded pretty good so I guessed it was all good but after a few days I noticed a thump sound coming out the speakers and then shortly after the fm signal would freeze and kill the sound. So I tried troubleshooting it. But couldn’t find anythin but while doing that I discovered my 9600 power amps were a little odd a little different, came to find out this 9600 have those addon (ic savers) boards on the power amp section Thought that was interesting and decided to take on this massive project and give it a try. Being this my first attempt to work on anything like this I was nervous,scared, and skeptical because I didn’t knew if these mods were going to work on this odd 9600 with the add on board. But feeling confident after fixing the original issue on the power supply b board and bringing this thing back to life after 10 years and thanks to all the information on this site I started restoration on dec 23 2018 and I was done by Jan 1 of 2019. I felt like a million bucks after successfully accomplishing this undertaking project.
Just have a few questions for you guys. Before the restoration. I noticed the left channel power indicator and the right channel power indicator didn’t exactly match well never did the left channel always reads lower, so I went and check for dc offset and I had 178mv on the left and like -1.? On the right. After restoration. At first fire up they were extremely close at .02 left channel and .05 on the righ so I felt proud and full of joy after accomplishing this. Now after couple of weeks after restoration and after about 10 minutes of listening to music I check for dc off set and it reads 14mv on the left and 15mv on the right. And the power meter still slightly lower on the right while listening to music. They about valence out when I turn the balance know slightly to the right. So this brings a little bit of concern so I just want to know if this is in a way normal or if I should replacing other components is this something I should worry about. Or just ignore it. I tried replacing the to3 transistors on the add on boards but could not find any good substitutes for the originals. Do I just replaced the mica insulator and applied new thermal paste. Also I noticed a moderate thump sound after shutting off power and I hear this right when the protection relay disengage, this was way worst before restoration. Any input and comments would be greatly appreciated
I have tons of videos and pictures of this projects. Thanks to all of you guys.
I did power supply B mod
Tuner mod, power supply A, also went and added an aluminum cased resistor to r-18 because I noticed it was getting hot and it had damaged the original c12 , I actually just used the aluminum case of a spare resistor I had bought for power supply B
Triac
Power amp
Led
Replace main filter caps with the obsolete Panasonics mentioned here that I found on eBay
And did a full recap on this massive amp. Nichicon gold, Nichicon muse, Elna silmic II,Wilma filmc, Ana some power series capacitors.
I don’t know if I’m forgetting to mention other things I did. Anyways my father purchased this amp back in 79-80 from a Canadian friend and I remember him enjoying this beauty until I graduated from high school in 2002. Last year I ask my dad about his old kenwood and he told me it had stopped working 10 years ago. So I went to his place picked up went through it and noticed power supply b was extremely burned and guessed that was the fault. So I went online and found videos on YouTube that lead me to this forum and sure enough I replaced those burned out resistors and this beast came back to life. It sounded pretty good so I guessed it was all good but after a few days I noticed a thump sound coming out the speakers and then shortly after the fm signal would freeze and kill the sound. So I tried troubleshooting it. But couldn’t find anythin but while doing that I discovered my 9600 power amps were a little odd a little different, came to find out this 9600 have those addon (ic savers) boards on the power amp section Thought that was interesting and decided to take on this massive project and give it a try. Being this my first attempt to work on anything like this I was nervous,scared, and skeptical because I didn’t knew if these mods were going to work on this odd 9600 with the add on board. But feeling confident after fixing the original issue on the power supply b board and bringing this thing back to life after 10 years and thanks to all the information on this site I started restoration on dec 23 2018 and I was done by Jan 1 of 2019. I felt like a million bucks after successfully accomplishing this undertaking project.
Just have a few questions for you guys. Before the restoration. I noticed the left channel power indicator and the right channel power indicator didn’t exactly match well never did the left channel always reads lower, so I went and check for dc offset and I had 178mv on the left and like -1.? On the right. After restoration. At first fire up they were extremely close at .02 left channel and .05 on the righ so I felt proud and full of joy after accomplishing this. Now after couple of weeks after restoration and after about 10 minutes of listening to music I check for dc off set and it reads 14mv on the left and 15mv on the right. And the power meter still slightly lower on the right while listening to music. They about valence out when I turn the balance know slightly to the right. So this brings a little bit of concern so I just want to know if this is in a way normal or if I should replacing other components is this something I should worry about. Or just ignore it. I tried replacing the to3 transistors on the add on boards but could not find any good substitutes for the originals. Do I just replaced the mica insulator and applied new thermal paste. Also I noticed a moderate thump sound after shutting off power and I hear this right when the protection relay disengage, this was way worst before restoration. Any input and comments would be greatly appreciated
I have tons of videos and pictures of this projects. Thanks to all of you guys.
Thanks
hopjohn
Silver Face
The power meters aren't useful for determining much of anything so I wouldn't worry over them. They certainly don't tell you anything about offset. About all they do tell you is that there is a slight imbalance in the meter calibration. So long as when the balance pot is centered the sound from the speakers seems level in both channels don't worry about it. If your dc offset measures as you say then it sounds like the amp is healthy. The thump is likely being caused due to switching over to LED. Some of the lights are responsible for draining the filter caps (I've forgotten which) at shutoff and LEDs won't do that as quickly as would incandescent lights resulting in some DC reaching the speakers on power down causing the thump.
Hopjohn beat me to it. It's the indicator lamps (am, fm, phono, aux etc.) that drain the caps. If you're getting a slight delay in the relays opening after powering off, that's what's causing it. A cure is to use incandescent lamps for those.
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Hey. Thanks so much for your input. I follow mostly your lead while doing this restoration. Your absolutely right. The thump sound came from the red stereo indicator led. It was not doing it before I found a red led so. I’m going to take a look at that. Before the red led from frys electronics I had a regular white led that I had painted red with a paint marker and it actually worked good. Just a lightly red tone. About the left and right channel.. I was so intrigued by this. I went and purchased an oscilloscope and again I’m not a pro I’m a straight roockie but reading online watching videos. I was able to hook it up to my 9600. I downloaded a tone generator app for my phone and used that to generate 1000hrtz tone and than out to the scope through 2 8ohm 200watt aluminum cased resistors from eBay. Well. The channels look pretty even going up in volume as long as I turn the valence pot slightly to the right. If it’s center. The right channel stays slightly under the left.
hopjohn
Silver Face
Yes, @gort69 has it right. In fact if you were to have a indicator bulb burnt out, on for example AUX, and turned the unit off with it set to AUX it would thump. If you then switch the amp over to an input where the indicator is working the thump goes away on power down. I'd follow gort's recommendation to replace the indicator bulbs with incandescent type.
I’ll change the leds to regular bulbs.
I’m thrilled with my 9600 after restoration. This one is going back to my father. He had tears coming down when he first heard the 96 after restoration. I just want it to be 100%. I just got done adding a cooling fan with separate power supply. And it keeps it ice cold
I’m thrilled with my 9600 after restoration. This one is going back to my father. He had tears coming down when he first heard the 96 after restoration. I just want it to be 100%. I just got done adding a cooling fan with separate power supply. And it keeps it ice cold
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hopjohn
Silver Face
Pretty sure that the actual input indicators are what's responsible for the draining of the caps, that's where the focus should be.
hopjohn
Silver Face
A lot is made of dropping resistors getting hot, and yes they do deteriorate the secondary supply board in these, but it is their job is to shed a lot of heat so that much is not unusual. Once they are dealt with as described by performing the high wattage replacements mod they shouldn't be cause for concern. I'm not sure an added fan would be necessary as the noise would be unwelcome to my ears, but whatever makes you happy.
Glad to hear about your Dad's joy, that's a touching moment. Thanks for sharing.
Glad to hear about your Dad's joy, that's a touching moment. Thanks for sharing.
Thanks sir I will up load a few pictures. I honestly believe. R-18 on power supply A board needs to be relocated because is so close to other components like c12. C12 onnmy amp was totally damaged. It had even shrieked the jacket and I could spin it 180 degrees left and right so I decided to relocated using the case from a spare resistor is had.
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Tell you the truth. I didn’t know what a diode was or what a transistor was maybe 6 months ago. I got my first kenwood from a neighbor (ka-9100). After that I begun watching videos and reading forums like this. After that I asked my father about his old 9600 I fixed it. Then I restored. From there I did a kenwood basic c2 restoration and upgrade. And as of now I’m doing another kenwood (ka3700). I had built custom cars and trucks from the ground up but electricity or electronics wasn’t really my thing. I’m a welder fabricator by trade. And a diy guy when I’m not working. I just have a sense of doing things 100% or don’t do em at all. I do consider my self very talented working with my hands and brain. Fast learner with the things I grow interest in. Here’s a little picture of my small ka3700 that I just finished at 12:30 am
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I'm impressed with the 9600 rebuild. I've built a few cars and think any kind of DIY/problem solving helps in many areas. Just knowing what tool to pull out of the tool box is a great first step.
Hopefully you are enjoying listening to these amps too. Kind of rewarding for sure.
Yes sir. Thanks for the message. I’m in the hunt for an unrestored 9600 because this one is going back to my father. This thing sound absolutely Amazing after restoration.
Hey. Thanks for the tip.
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