Hello
I have one Hifonics Zeus amplifier which has a defect.
Somebody else tried to repair it before me.
After this I found the following:
• transistors from the power supply have been changed with IRFZ 44 N (I don’t know if this is the exact required one)
• gate resistor (from the above transistor) I found as 220ohms and I replace it with a 82ohms (I don’t know if this is the exact required one)
• the driver transistor for the power supply transistor have been replaced with a BC 639 (I don’t know if this is the exact required one); in parallel with this emitter resistor (of this transistor) which has the value of 56ohms has been added a 75ohms resistor
• one of the rectifier diode was replaced with two diodes of lower current in parallel in case TO220 (the original one was in case TO 243)
• I have found one of the audio output stage transistor (TIP35C) defect; I have replaced all the five transistors which were connected in parallel
The amplifier has the following symptoms:
• without audio signal the idle current it is about 0,85A, and every thing looks OK
• with audio signal and a absorbed current of around 40A, the transformer from the power supply gets very warm (abnormal)
Questions:
1. Is it possible that the reason of this defect has something to do with the “vario power circuit”? (I am thinking this way because of the fact that even for that 40A current; the voltage from collector of the audio output stage transistor is only 19V).
2. Which are the switching conditions of the vario power? Is it the input audio level a reference for the switching criteria
3. Which are the threshold values for switching of the three voltages (19V, 36V, 56V)?
Thank for your attention.
Looking forward for your answer.
I have one Hifonics Zeus amplifier which has a defect.
Somebody else tried to repair it before me.
After this I found the following:
• transistors from the power supply have been changed with IRFZ 44 N (I don’t know if this is the exact required one)
• gate resistor (from the above transistor) I found as 220ohms and I replace it with a 82ohms (I don’t know if this is the exact required one)
• the driver transistor for the power supply transistor have been replaced with a BC 639 (I don’t know if this is the exact required one); in parallel with this emitter resistor (of this transistor) which has the value of 56ohms has been added a 75ohms resistor
• one of the rectifier diode was replaced with two diodes of lower current in parallel in case TO220 (the original one was in case TO 243)
• I have found one of the audio output stage transistor (TIP35C) defect; I have replaced all the five transistors which were connected in parallel
The amplifier has the following symptoms:
• without audio signal the idle current it is about 0,85A, and every thing looks OK
• with audio signal and a absorbed current of around 40A, the transformer from the power supply gets very warm (abnormal)
Questions:
1. Is it possible that the reason of this defect has something to do with the “vario power circuit”? (I am thinking this way because of the fact that even for that 40A current; the voltage from collector of the audio output stage transistor is only 19V).
2. Which are the switching conditions of the vario power? Is it the input audio level a reference for the switching criteria
3. Which are the threshold values for switching of the three voltages (19V, 36V, 56V)?
Thank for your attention.
Looking forward for your answer.
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