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Kenwood KR-6160 bias and DC balance conundrum

tonefoto

tonefoto

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I have a question for anybody familiar with the Kenwood KR-6160 cap coupled receiver. Its got a great sound, ton of low end oomph. My question is and still remains; What do the 2 trimmers on the driver board do? The common belief is the bias adjustment. My KR-6160 when adjusted for 9.3 MV bias will resullt in a huge imbalance in the output coupling cap voltage, (65VDC and 36VDC). Conversely, if I use the trimmers to adjust the DC balance on the output caps, the bias will shoot up to 65mV or more on one channel. So, does anybody have a solution how to adjust the KR-6160 bias AND balance the voltage on the output caps like I do on most cap-coupled amps?

thank you for your sage advice.
 
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tonefoto said:
I have a question for anybody familiar with the Kenwood KR-6160 cap coupled receiver. Its got a great sound, ton of low end oomph. My question is and still remains; What do the 2 trimmers on the driver board do? The common belief is the bias adjustment. My KR-6160 when adjusted for 9.3 MV bias will resullt in a huge imbalance in the output coupling cap voltage, (65VDC and 36VDC). Conversely, if I use the trimmers to adjust the DC balance on the output caps, the bias will shoot up to 65mV or more on one channel. So, does anybody have a solution how to adjust the KR-6160 bias AND balance the voltage on the output caps like I do on most cap-coupled amps?

thank you for your sage advice.
Click to expand...
Have you adjusted bias correctly? Here's a link that shows how it's done:
https://audiokarma.org/forums/index...rent-bias-in-kenwood-kr-6160-receiver.811996/
 
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It's cap coupled. DC balance isn't adjustable on a cap coupled amp. The caps remove the DC component before it goes to the speakers (as long as they're not leaky). So the trimmers adjust bias. And some quasi-complementary amps also have trimmers to adjust the mid-point voltage. I don't know if the 6160 is quasi-complementary but my 5150 is. If your output transistors are all NPN's, it is quasi-complementary and if you have two extra trimmers on the amp board, they're for adjusting the mid-point. Often the service manual for such an amp will tell you to adjust those trimmers for symmetrical clipping using a scope, which is probably the better way to adjust it since it will account for slight differences between your output transistors.
 
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You have some work to do. With everything working correctly, you would set the voltage on the + side of the caps to approx 50% of the rail voltage and then the bias across the emitter resistors. I have a 4140 and a 6160 but it’s been a couple years since I did the restoration. There should be no interplay between the center voltage and the bias. My first guess would be power related, under load the regulator is losing its stability. If it hasn’t been recapped, the coupling caps need to go and the power regulator section.

But… there may only be a bias setting. Get that set first. This thread outlines the how to https://audiokarma.org/forums/index...rent-bias-in-kenwood-kr-6160-receiver.811996/
 
jefferylhenr said:
You have some work to do. With everything working correctly, you would set the voltage on the + side of the caps to approx 50% of the rail voltage and then the bias across the emitter resistors. I have a 4140 and a 6160 but it’s been a couple years since I did the restoration. There should be no interplay between the center voltage and the bias. My first guess would be power related, under load the regulator is losing its stability. If it hasn’t been recapped, the coupling caps need to go and the power regulator section.

But… there may only be a bias setting. Get that set first. This thread outlines the how to https://audiokarma.org/forums/index...rent-bias-in-kenwood-kr-6160-receiver.811996/
Click to expand...
I l appreciate the great responses so far, thank you all. So I will recap the power supply first and then the amp section. Sounds like I would adjust DC balance forsymetricalclipping then go back and adjust bias to a reasonable levelaround 10mV or less. If I'm getting this right.
 
tonefoto said:
I l appreciate the great responses so far, thank you all. So I will recap the power supply first and then the amp section. Sounds like I would adjust DC balance forsymetricalclipping then go back and adjust bias to a reasonable levelaround 10mV or less. If I'm getting this right.
Click to expand...
So far I've replaced the coupling caps and main filter cap, using 4700uf 100V and 2 3300uf 100V Epcos. After adjusting bias to 9.4mV center balance on the coupling caps ia at 38 VDC on both. Will get to the voltage regulator board next
 
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