Hey guys, sorry to come at you, yet again with a problem and hope to get this solved. My XXV Sampson was poorly packed and was damaged during shipping. After removing the bottom plate and inspecting the internals I found no damage, the damage was done to the end plate(where rca inputs are located) and mounting feet on the other end. I proceeded to power it up, immediately heard a squealing sound and after 4-5 secs a loud pop. I was watching my dmm and didn't notice where the pop came from but found that pin 5 of the irs21844s(U7), and the tops of a TL072(U4) and LM211(U3) blew off.
I removed the output driver board and replaced the bad parts including the other opamps.
I wanted to test if the amp was going to power up but the only indication was 1 of the 3 output relays switched, no lights or anything, oh, the cooling fan worked also. I seperated the supply and output boards, replaced the supply drivers with BD139/BD140 transistors. The amp still won't power up. I get 11.97V on pins 9 & 10 of the 7500bd on the power supply board and scope produces a descent wave
but gets worse the closer to the gate resistor. This is 4.7V at the supply drivers
and .04V at the gate resistor, which are testing at 47 ohm
I have removed the power supply board and checked for damage and bad traces, currently waiting for a new output driver board from Crescendo Audio.
power supply board
I'm still new to this, most of the troubleshooting done so far has been done with the assistance of a buddy who's more knowledgable and could fix it if I were to ship it to him but I don't want it to get damaged any more than it has been and he has a ton of other amps to repair. I could use a little more guidance on where to go with this thing. Any help is greatly appreciated.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I removed the output driver board and replaced the bad parts including the other opamps.
I wanted to test if the amp was going to power up but the only indication was 1 of the 3 output relays switched, no lights or anything, oh, the cooling fan worked also. I seperated the supply and output boards, replaced the supply drivers with BD139/BD140 transistors. The amp still won't power up. I get 11.97V on pins 9 & 10 of the 7500bd on the power supply board and scope produces a descent wave
An externally hosted image should be here but it was not working when we last tested it.
but gets worse the closer to the gate resistor. This is 4.7V at the supply drivers
An externally hosted image should be here but it was not working when we last tested it.
and .04V at the gate resistor, which are testing at 47 ohm
An externally hosted image should be here but it was not working when we last tested it.
I have removed the power supply board and checked for damage and bad traces, currently waiting for a new output driver board from Crescendo Audio.
power supply board
An externally hosted image should be here but it was not working when we last tested it.
I'm still new to this, most of the troubleshooting done so far has been done with the assistance of a buddy who's more knowledgable and could fix it if I were to ship it to him but I don't want it to get damaged any more than it has been and he has a ton of other amps to repair. I could use a little more guidance on where to go with this thing. Any help is greatly appreciated.
If the photo of U3 and U4 are from your amp, the tops weren't blown off. The manufacturer defaced them so the numbers couldn't be read.
For the scope images to be useful, you need to use DC coupling. If you have the trace referenced to anything other than the center reference line, you need to note that when posting the image.
If you had 12v on pins 9 and 11, you would also have approximately that on the gates of the power supply FETs. That should cause excessive current draw unless the FETs are blown.
What was the cost of the driver board from the manufacturer?
For the scope images to be useful, you need to use DC coupling. If you have the trace referenced to anything other than the center reference line, you need to note that when posting the image.
If you had 12v on pins 9 and 11, you would also have approximately that on the gates of the power supply FETs. That should cause excessive current draw unless the FETs are blown.
What was the cost of the driver board from the manufacturer?
Still working on this problem of an amp, it's at the repair man at the moment but would help him alot if we could get a board schematic for the amplifier. We need to verify the supply drivers and which locations they go and direction, also the supply and output fets. If anyone could help, if anyone knows which fets are used on the supply and output, which 2 transistors are used for drivers and which location they go in, or better a schematic i would greatly appreciate it.
the drivers were replaced with the same part, placed in the same locations and the same direction and he lost voltage at the driver, but he changed the direction of 1 group and voltage was good past the drivers up to the gate resistors. any help thanks!!
the drivers were replaced with the same part, placed in the same locations and the same direction and he lost voltage at the driver, but he changed the direction of 1 group and voltage was good past the drivers up to the gate resistors. any help thanks!!
I can't remember been awhile since I worked on one of these amps .. But there is either 4 or 8 drives for the power supply fets ..
The collector (middle leg) of the pnp driver transistors should be directly connected to ground .. As far as the direction they face it should be printed on the circuit board in silk screen ..
If I remember correctly the amp uses IRFP064N as the power supply fets ..
The outputs are IRFP460LC also of the outputs failed the IR21844S driver ic's need to be replaced on the audio driver board ..
The collector (middle leg) of the pnp driver transistors should be directly connected to ground .. As far as the direction they face it should be printed on the circuit board in silk screen ..
If I remember correctly the amp uses IRFP064N as the power supply fets ..
The outputs are IRFP460LC also of the outputs failed the IR21844S driver ic's need to be replaced on the audio driver board ..
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