Hey guys. So got this amp in with blown outputs.(640Ns)
Before I just threw new ones in I scoped the pads. On one side of the amp the wave was perfect square wave. The other side was like a sine wave.
So I did a few more checks and noticed 1 of the buffer chips had died (2T)
Replaced that. As well as checked components on the driver board which all apprear to be ok. As I've come to notice amps that run buffer chips usually they let go and the driver board survives. ?
Anyway. I fitted up all brand new fets all 8. (4 each side)
I was putting the (sine wave) down to there is a high and a low side and I think I remember one of them U can never get a proper reading from. So made sence that I was only getting a square wave on one side..
Anyway fitted new fets. Have audio but very weak and sounds not very good. Also the louder U go the fets on both sides (more so the side with the sine wave) gets very hot. So I shut it down for further probing. And I can see the 2X buffer that has the usual hole in the top that U come to find when they have taken a hit. (But reads ok?) So about to swap that out but just looking for suggestions. I do not have any scope photos but can get them if requested.
All 10ohm gate resistors have been replaced. I'm having trouble uploading photos so I'll try again soon
Edit. Have checked all the new mosfets on a transistor tester and the 'VT' are the same or within 0.1v of each other
Before I just threw new ones in I scoped the pads. On one side of the amp the wave was perfect square wave. The other side was like a sine wave.
So I did a few more checks and noticed 1 of the buffer chips had died (2T)
Replaced that. As well as checked components on the driver board which all apprear to be ok. As I've come to notice amps that run buffer chips usually they let go and the driver board survives. ?
Anyway. I fitted up all brand new fets all 8. (4 each side)
I was putting the (sine wave) down to there is a high and a low side and I think I remember one of them U can never get a proper reading from. So made sence that I was only getting a square wave on one side..
Anyway fitted new fets. Have audio but very weak and sounds not very good. Also the louder U go the fets on both sides (more so the side with the sine wave) gets very hot. So I shut it down for further probing. And I can see the 2X buffer that has the usual hole in the top that U come to find when they have taken a hit. (But reads ok?) So about to swap that out but just looking for suggestions. I do not have any scope photos but can get them if requested.
All 10ohm gate resistors have been replaced. I'm having trouble uploading photos so I'll try again soon
Edit. Have checked all the new mosfets on a transistor tester and the 'VT' are the same or within 0.1v of each other
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I find it easier to troubleshoot these amps with the outputs in the circuit and the rectifiers out of the circuit. That will give you a better idea of the condition of the drive circuit.
The driver boards are isolated from the outputs by the optocouplers which protects the driver boards in these amps.
The driver boards are isolated from the outputs by the optocouplers which protects the driver boards in these amps.
Ok I can do that. Just so I can learn. This would just disable the rail voltage correct? But I will still get the nessassary voltages to the drive board to track stuff?
Perry could U please send me a photo of an "octocopler' just so I can find it on this board sorry if I miss spelt that. Also could this be faulty and the cause of the MOSFETs heating up and bad sound?
Indicated by the green arrows in the photo and on the last page of the attached PDF file.The part number is 6N137.
http://www.bcae1.com/temp/SLA1500.pdf
http://www.bcae1.com/temp/SLA1500.pdf
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Ok yes I have a short of 5.3 ohms on pin 3 and 5. But that to me would indicate a short elseware as it's a bit high for a shorted chip.
None the less I'm going to pull it and check. Part numbers have been rubbed off but have a parts amp here I can get stuff off I'll let u know how it goes 🤞
None the less I'm going to pull it and check. Part numbers have been rubbed off but have a parts amp here I can get stuff off I'll let u know how it goes 🤞
Pulled the chip and there is still a short of 6ohms across pins 3 and 5. Chip it's self does not have a short
Would be very very handy if I could upload pictures because there is a 2X buffer chip that looks suspect.
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Preview post to see how the post will look.
Click Submit Reply to send it to the forum.
Yes it just loads about half the page and just stops. Left it for 10 mins and it still won't upload a single picture. There must be a problem with the website
I just can't quiet read if it's a 2T or a 2X as the burned bit it right where the letter is. I'm 99% sure it's a 2X but can't be sure
The files are too large. When you click the 'manage attachments' button, maximize the page and scroll down to see the file size limits.
Do you have a computer?
Do you have a computer?
