Kicker kx350.2 biasing issue - diyAudio
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Old 20th October 2012, 02:21 AM   #1
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Default Kicker kx350.2 biasing issue

Hello again. Sittin here with an old kicker amp. Left channel is getting a very high voltage bias. I'm just curious if anyone is knowledgable on auto biasing circuitry in these older amps. Is there a better I.c to upgrade? I'm gettin 30 volts across Base. Causes amp to go haywire. Any thoughts?
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Old 20th October 2012, 06:19 PM   #2
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The KX series of amps are class B so there is no bias current.

Which IC are you referring to?

What do you mean by 30v across base?
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Old 20th October 2012, 08:21 PM   #3
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Default High voltage on base of transistoes

Quote:
Originally Posted by Perry Babin View Post
The KX series of amps are class B so there is no bias current.

Which IC are you referring to?

What do you mean by 30v across base?
Long night, anyway the tip 35 /36 is receiving 30 volts on the base where the right channel that works is not.
Leg 1 base. 30 volts or so is where we're at.
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Old 20th October 2012, 10:01 PM   #4
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So you have 30v across the speaker terminals for that channel?
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Old 21st October 2012, 03:56 AM   #5
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No there's no voltage on speaker terminals, but as soon as you put the transistors back in circuit it goes haywire with current draw. No issues with transistors. Those are good. Just imagine meter ground on RCA shield, positive on all 3 legs 30 volts or so.
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Old 21st October 2012, 08:59 AM   #6
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You can't use the DC voltage on the base without having the outputs in place. It breaks the feedback loop and makes the drive circuit swing fully to one rail or the other. What precisely does the amp do when the outputs are in the circuit?

Does is do the same thing when using a current limiter in the B+ line?

I'm assuming that you've checked the driver transistors and they're not leaking or shorted.
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Old 21st October 2012, 09:38 AM   #7
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As soon as output is in circuit, it draws full current. As if it was shorted. With no audio, or any input. Outputs are all fine, no shorts.
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Old 21st October 2012, 03:18 PM   #8
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If you short the collector/emitter legs of the transistor between the output transistors, does that allow the amp to power up?
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Old 21st October 2012, 03:52 PM   #9
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I had a ZX350.2 with a similar symptom. I found a broken solder joint on one of the jumpers in the bias circuit. It was not visibly broken, I could only tell by measuring.
(My first comment here, I just joined)
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Old 21st October 2012, 08:42 PM   #10
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I will try that Perry, I will post back with results shortly.
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