Hello,
I have faulty Axton c408 amp and I need some help. One channel dead, on high current (car battery), PSU mosfets Q43;Q42 (FPQ50N06) burning. I figure out problem is not PSU. Without rear transistors Q211/Q213 and Q210/Q212 bad channel stops burning PSU Q43/Q42 mosfets. Now voltage +-35Volts ok. But channel still faulty anyway. So I did try figure out why this channel eat to much current. I did check all transistors seems they are ok no shorts. I have desolder Q216 and amp come in protect mode. Now I am getting none voltage on PSU at all. Okay I did solder back this Q216 and protect mode gone. But after 2-3 minutes testing faulty channel, protect mode comes again. Anyway there is no voltage on this channel because -+35v traces cut off. So now I believe something wrong with digital section wont turn on amp at all, protection mode. There is few chips NJM2068 (IC22A) and KA7500BD (IC21) they control this. Could some one explain how this section works? I have pdf these chips, I am confuse... Could some one spend few minutes and help me...
I have faulty Axton c408 amp and I need some help. One channel dead, on high current (car battery), PSU mosfets Q43;Q42 (FPQ50N06) burning. I figure out problem is not PSU. Without rear transistors Q211/Q213 and Q210/Q212 bad channel stops burning PSU Q43/Q42 mosfets. Now voltage +-35Volts ok. But channel still faulty anyway. So I did try figure out why this channel eat to much current. I did check all transistors seems they are ok no shorts. I have desolder Q216 and amp come in protect mode. Now I am getting none voltage on PSU at all. Okay I did solder back this Q216 and protect mode gone. But after 2-3 minutes testing faulty channel, protect mode comes again. Anyway there is no voltage on this channel because -+35v traces cut off. So now I believe something wrong with digital section wont turn on amp at all, protection mode. There is few chips NJM2068 (IC22A) and KA7500BD (IC21) they control this. Could some one explain how this section works? I have pdf these chips, I am confuse... Could some one spend few minutes and help me...
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Removing Q1 will defeat much of the protection circuit.
It appears that you're stating that the positive rail has excessive current flow but not the negative rail. Is that correct?
It appears that you're stating that the positive rail has excessive current flow but not the negative rail. Is that correct?
YES. I did try disconnect positive +35v trace (desolder q210 / q212) and than no burning Q43/ Q42 fets, but anyway channel wont work without proper voltage. q210 / q212 are ok no shorts tested. Perry if u need more details voltage on pins I can post to u!
Thank`s
Thank`s
thanks. I will try remove q1, that protection mode kills me... Lets burn parts 🙂
Yes positive rail has high current, my lab psu can`t handle over 5A none inputs mode. Negative ok. Check block diagram, if u need voltage on pins, I will tell u!
Yes positive rail has high current, my lab psu can`t handle over 5A none inputs mode. Negative ok. Check block diagram, if u need voltage on pins, I will tell u!
It's extremely unusual for high current to be passing through the positive rail and not through the negative rail. None of the high current devices on the output stage connect to ground (the only other path generally available for high current to pass).
What resistance do you read across the two speaker terminals for the defective channel?
What resistance do you read across the two speaker terminals for the defective channel?
Thanks Perry for your help! resistance about 1700 ohms. I will try external transformer +-35v, and I will see where is a problem, because protect mode cut off voltage...
with q1 out protection off. Thanks Perry! Now I found few faulty transistors Q207 C3198 and Q209 B631K. Today I will replace them, if everything ok I solder back Q1 and check protection!
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