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Error in Amplifier Circuit Input 60v

04/02/2017 9:51 AM

this is my circuit .... i run it with my 60v DC and then R13(330r) instanly got fire . any thing seem to be right but i do it the second times and get the same result. i dont know where is the problem.. pls help me.... thank you so much.

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#1

Re: error in Amplifier circuit input 60v

04/02/2017 10:14 AM

A schematic would be MUCH more helpful.

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#2

Re: error in Amplifier circuit input 60v

04/02/2017 10:23 AM

Have you done any calculations on how much power that resistor has to dissipate?

Or for that matter, have you do any calculations on anything regarding your circuit design at all?

60 volts across a 330 ohm resistor would allow ~182 milliamps of current to flow. 182 mA @60V is 10.9 watts.

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#4
In reply to #2

Re: error in Amplifier circuit input 60v

04/02/2017 11:22 AM

i make this after my lecture s circuit..... all of my accessories are just like him....my friend make the same circuit and it run easily

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#3

Re: error in Amplifier circuit input 60v

04/02/2017 11:09 AM

I think I see a way for you to fix this. It looks like this circuit board was designed by a company named Tang Day Keo. If you contact them they should be able to tell you where your copy of their circuit is in error. It might be as simple a typographic error [3r30 instead of 330r] for the value of one of the components.

Contact them today, I'm sure they want to hear from you.

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#5

Re: Error in Amplifier Circuit Input 60v

04/02/2017 12:29 PM

My guess is that you have a solder bridge somewhere. Examine the board carefully, with a magnifying class if necessary. Also look for cold (crystallized) solder joints. Check to see if you have an electrolytic capacitor in backwards. Check to see if there is a diode installed backwards. Make sure the transistors are installed correctly.

I hope this helps.

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#6
In reply to #5

Re: Error in Amplifier Circuit Input 60v

04/02/2017 12:52 PM
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#7

Re: Error in Amplifier Circuit Input 60v

04/02/2017 10:21 PM

please post the schematic diagram, or a link to it.

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#8

Re: Error in Amplifier Circuit Input 60v

04/03/2017 1:24 AM

It is very likely that you are applying the 60V on the 330R resistor, which means a bit more of 10W. Your resistor must be rated for less than 1W, so it burns instantly.

If this is supposed to work, compare the input impedance of your circuit with the one that works, and go component by component until you find the error.

Apart form a solder joint, it could also be a soft start not implemented properly. The hardware could be the same, but if your software is different, I would not be suprised to see the circuit behave differently.

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#9

Re: Error in Amplifier Circuit Input 60v

04/03/2017 12:53 PM

60V is an awful lot of volts for an amplifier circuit running without heat sinks. Should it be 6V?

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#10
In reply to #9

Re: Error in Amplifier Circuit Input 60v

04/03/2017 2:04 PM

A Class-D would probably be OK. But it's hard to tell without more information.

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#11
In reply to #10

Re: Error in Amplifier Circuit Input 60v

04/03/2017 5:57 PM

True, but I would find it very hard to convince myself that that was a class D circuit.

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#12

Re: Error in Amplifier Circuit Input 60v

04/03/2017 7:20 PM

This is a Class AB linear audio amp, with differential input pair, a class A pre-driver, and complementary output as Darlington made from individual BJT. There's NO current limit or short circuit protection. I expect if R13 is burning up then either the output capacitor is shorted (installed as wrong polarity) or a solder bridge or hairline short circuit of the PCB, from output to ground. The lack of any SOA protection for the output transistors makes this design rather crude and prone to self-destruction if you oveload or short circuit the output. Q6 might also be failed into short circuit, as a result of repeated attempts to replace R13, without finding/solving the root-cause.

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#13
In reply to #12

Re: Error in Amplifier Circuit Input 60v

04/03/2017 9:24 PM

Really? How is it that you know this? You, t_b_l, were the one who asked for a schematic. Did one magically appear to you?

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#14
In reply to #13

Re: Error in Amplifier Circuit Input 60v

04/03/2017 9:41 PM

I followed the PCB traces. :-)

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#16
In reply to #14

Re: Error in Amplifier Circuit Input 60v

04/04/2017 10:27 AM

Certainly more motivated than me.

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#15
In reply to #12

Re: Error in Amplifier Circuit Input 60v

04/04/2017 9:53 AM

I put the couple transistors q6 and q7 to the wrong posistion in real circuit . I put q6 to the q7 position and q7 to q6 s position.... did that make my r13 get burn..

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#17
In reply to #15

Re: Error in Amplifier Circuit Input 60v

04/04/2017 10:30 AM

Yes, it would explain everything. You swapped a PNP for an NPN, and vice versa. Instead of the base collection junction being reversed biased, it would have acted like a forward conducting diode. Base emitter junction would be reversed, but it does not block above 6-12V. A little know property of the base-emitter in reverse is that it behaves much like a zener diode. The other 3.9 ohm resistor at R13 also would have heated up, but because your output capacitor also has to charge up the load, I would expect R13 burns up first.

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#18
In reply to #17

Re: Error in Amplifier Circuit Input 60v

04/04/2017 10:33 AM

By the way, if this drives a loudspeaker, a value of 330 ohms is much too high. I would expect it to be 3.9 ohms, or even 0.39 ohms; otherwise you don't get much power out.

What is this amplifier used for? What is the load that you connect to it???

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#19
In reply to #17

Re: Error in Amplifier Circuit Input 60v

04/04/2017 11:28 AM

So to solve that i just need to swap those trans to the right position or i have to make a new circuit.

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#20
In reply to #19

Re: Error in Amplifier Circuit Input 60v

04/04/2017 12:03 PM

You should always test the other related components rather than assume the are OK.

You could easily have blown other transistors and/or diodes.

You did not answer if you are sure R13 is 330 ohms?

Your output transistor emitters will each have a low value resistor between them and the load. I can't see clearly where R13 is, you don't give the schematic, and you don't answer what the load will be...

Because of all that, I don't guarantee my answer is a full and complete solution in your case.

Anytime you de-solder parts, test them out of circuit before re-installing them or install a new virgin part. When parts are removed, it's a good opportunity to "in-circuit" test other parts connecting around to it.

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