Excellent, thank you for that!
I have already found one of the main transistors tests bad so i think i may have found the issue.
Cheers
Mark
I could do with a little help here if anybody has any suggestions. The amp powers on and immediately goes into fault mode. I ran through the basic checks in the manual and eliminated the possibility of shorted output transistors, i even went as far as removing the four heatsinks and testing all 16 output devices (MJ15024 & MJ150125) as well as all the other devices attached to the four heatsinks and everything seemed healthy with the exception of one MJ15024 which had a beta of 5 vs all the others in the amp which were in the 50-60 range so i replaced that one unit.
The first stage of the power supply is working with 320v+ across the filter cap bank feeding into the switching part of the supply, and the second power supply for generating 5v for the standby circuit is working correctly too. From what I can tell everything in the power supply seems to be working fine, it’s just the main HV switching supply is being shut down by the protection circuit.
There is a small section in service manual about the DC protection circuit saying that pin 9 of its IC will be at 5V if ok, or pulled down to 0v if there is DC on the outputs. I am seeing 5v on that pin and when I power up the amp it immediately goes into fault mode, and that pin slowly drops to 0v after 5-10seconds. So it is detecting DC, but I don’t think that is the main issue as the amp shutdowns the power supply and goes into protect mode long before that part of the circuit drop from 5volts.
The second part of the protection circuit deals with bridge imbalance detection, which feeds a voltage into the protection IC if there is an issue, and I am seeing .4v there immediately after power on so I am almost certain that is what is tripping the protection circuit.
This is where I am stuck, what do I look at next to figure out where the issue lies? As above i can’t find any shorts on the output transistors from pin to pin, or shorts to the heatsink, or any odd resistance readings from each of their pins to ground. This is also a four channel amplifier and I can’t even figure out a way to determine which of the four channels has the issue.
I couldn’t find a schematic for this specific model (Crown XS4300), but I have found a service book and schematic for the XS1200 (2 channel version), and schematic for the Pulse 4X300 which according to the Crown forum is the same amp. The Pulse seems to have a little more circuitry than mine, but both are relevant.
Help!
The first stage of the power supply is working with 320v+ across the filter cap bank feeding into the switching part of the supply, and the second power supply for generating 5v for the standby circuit is working correctly too. From what I can tell everything in the power supply seems to be working fine, it’s just the main HV switching supply is being shut down by the protection circuit.
There is a small section in service manual about the DC protection circuit saying that pin 9 of its IC will be at 5V if ok, or pulled down to 0v if there is DC on the outputs. I am seeing 5v on that pin and when I power up the amp it immediately goes into fault mode, and that pin slowly drops to 0v after 5-10seconds. So it is detecting DC, but I don’t think that is the main issue as the amp shutdowns the power supply and goes into protect mode long before that part of the circuit drop from 5volts.
The second part of the protection circuit deals with bridge imbalance detection, which feeds a voltage into the protection IC if there is an issue, and I am seeing .4v there immediately after power on so I am almost certain that is what is tripping the protection circuit.
This is where I am stuck, what do I look at next to figure out where the issue lies? As above i can’t find any shorts on the output transistors from pin to pin, or shorts to the heatsink, or any odd resistance readings from each of their pins to ground. This is also a four channel amplifier and I can’t even figure out a way to determine which of the four channels has the issue.
I couldn’t find a schematic for this specific model (Crown XS4300), but I have found a service book and schematic for the XS1200 (2 channel version), and schematic for the Pulse 4X300 which according to the Crown forum is the same amp. The Pulse seems to have a little more circuitry than mine, but both are relevant.
Help!
I could do with a little help here if anybody has any suggestions. The amp powers on and immediately goes into fault mode. I ran through the basic checks in the manual and eliminated the possibility of shorted output transistors, i even went as far as removing the four heatsinks and testing all 16 output devices (MJ15024 & MJ150125) as well as all the other devices attached to the four heatsinks and everything seemed healthy with the exception of one MJ15024 which had a beta of 5 vs all the others in the amp which were in the 50-60 range so i replaced that one unit.
The first stage of the power supply is working with 320v+ across the filter cap bank feeding into the switching part of the supply, and the second power supply for generating 5v for the standby circuit is working correctly too. From what I can tell everything in the power supply seems to be working fine, it’s just the main HV switching supply is being shut down by the protection circuit.
There is a small section in service manual about the DC protection circuit saying that pin 9 of its IC will be at 5V if ok, or pulled down to 0v if there is DC on the outputs. I am seeing 5v on that pin and when I power up the amp it immediately goes into fault mode, and that pin slowly drops to 0v after 5-10seconds. So it is detecting DC, but I don’t think that is the main issue as the amp shutdowns the power supply and goes into protect mode long before that part of the circuit drop from 5volts.
The second part of the protection circuit deals with bridge imbalance detection, which feeds a voltage into the protection IC if there is an issue, and I am seeing .4v there immediately after power on so I am almost certain that is what is tripping the protection circuit.
This is where I am stuck, what do I look at next to figure out where the issue lies? As above i can’t find any shorts on the output transistors from pin to pin, or shorts to the heatsink, or any odd resistance readings from each of their pins to ground. This is also a four channel amplifier and I can’t even figure out a way to determine which of the four channels has the issue.
I couldn’t find a schematic for this specific model (Crown XS4300), but I have found a service book and schematic for the XS1200 (2 channel version), and schematic for the Pulse 4X300 which according to the Crown forum is the same amp. The Pulse seems to have a little more circuitry than mine, but both are relevant.
Help!
thank you ขอบคุณครับผม