Hi its me again...
The story thus far. One channel works great, which emboldened me to build the second.
The second one not so good. The history of the not so good channel is this:
1. With the chassis open, and everything in place I tested it on an old pair of speakers and a beautiful melodious sound eminated.
2. Put the two halves of the chassis together and a serious hum appeared.
3. After much poking and disassembling i discovered that the JFET was grounding through a washer (damn those fets are small) onto the chassis. When the two halves were not joined the voltage didn't go anywhere, upen closing the voltage was draining out through the speaker terminal, by way of the star ground... I think
4. Great i thought, just to make sure i pulled the FET off and with it hanging in space i tried the amp again, and it all seemed fine, reatatched the FET and all looked good.
5..... or so it seemed. After an hour "POP" and no sound.
So know i am sure something has blown. I am new to this and this is about as much as i have managed to determine.
1. At the DC i measure a potential difference of 52V which is higher then the 46V that i was getting before and the 46V on the still working channel.
2. Where i used to measure the voltage at R18 and R7 and set it at 23V (half of 46V) I get almost nothing, 2 or 3 volts.
3. At the speaker terminals there appears to be a very minor extremely unstable something in the millivolts and a minor pop st the speaker on power off.
I have order more JFET's because i assume the JFET has gone and possible the MOSFET's.
How can i trouble shoot this, maybe a resitor went or something else? No burn marks on board so no serious short.
Ant and all help would be greatly appreciated
Thanks
The story thus far. One channel works great, which emboldened me to build the second.
The second one not so good. The history of the not so good channel is this:
1. With the chassis open, and everything in place I tested it on an old pair of speakers and a beautiful melodious sound eminated.
2. Put the two halves of the chassis together and a serious hum appeared.
3. After much poking and disassembling i discovered that the JFET was grounding through a washer (damn those fets are small) onto the chassis. When the two halves were not joined the voltage didn't go anywhere, upen closing the voltage was draining out through the speaker terminal, by way of the star ground... I think
4. Great i thought, just to make sure i pulled the FET off and with it hanging in space i tried the amp again, and it all seemed fine, reatatched the FET and all looked good.
5..... or so it seemed. After an hour "POP" and no sound.
So know i am sure something has blown. I am new to this and this is about as much as i have managed to determine.
1. At the DC i measure a potential difference of 52V which is higher then the 46V that i was getting before and the 46V on the still working channel.
2. Where i used to measure the voltage at R18 and R7 and set it at 23V (half of 46V) I get almost nothing, 2 or 3 volts.
3. At the speaker terminals there appears to be a very minor extremely unstable something in the millivolts and a minor pop st the speaker on power off.
I have order more JFET's because i assume the JFET has gone and possible the MOSFET's.
How can i trouble shoot this, maybe a resitor went or something else? No burn marks on board so no serious short.
Ant and all help would be greatly appreciated
Thanks
?
I'm using clips bought from Mouser in combination with AluOX insulators and thermal grease.
They are not avaible in the right format for the JFET but I used the smallest size they sell at mouser and it seems to be working. I've acutally tested my Zv9 for the first time today, everything seems to work - only final assembly left.
The picture below may give you the idea even though the JFET is not visible...
They are not avaible in the right format for the JFET but I used the smallest size they sell at mouser and it seems to be working. I've acutally tested my Zv9 for the first time today, everything seems to work - only final assembly left.
The picture below may give you the idea even though the JFET is not visible...
Attachments
Hi,
I'm casing up my ZV9 based on Veteran/Peter Daniel's boards. When everything is wired up with star ground to mains earth through thermistors the fuse blows while powering up through a variac. I've removed the lead from the star ground to mains earth and power up with no problem but I measure the full rail voltage potential between the star ground and mains earth. Every thing seems right and the fets are insulated with mica and silicone paste. I've studied many examples of the star grounding scheme posted here and I can find nothing obviously wrong. Thanks for any guidance.
Rick
I'm casing up my ZV9 based on Veteran/Peter Daniel's boards. When everything is wired up with star ground to mains earth through thermistors the fuse blows while powering up through a variac. I've removed the lead from the star ground to mains earth and power up with no problem but I measure the full rail voltage potential between the star ground and mains earth. Every thing seems right and the fets are insulated with mica and silicone paste. I've studied many examples of the star grounding scheme posted here and I can find nothing obviously wrong. Thanks for any guidance.
Rick
Here's a wiring diagram posted earlier using Peter and Veterans board.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=93348&pagenumber=3
SMathews
http://www.diyaudio.com/forums/showthread.php?s=&threadid=93348&pagenumber=3
SMathews
help please
I am posting to this thread to see if anyone can help me with my Zv9. I got it all together and only one channel is working. The one that is not working is still getting warm and there is a slight hum from the speaker. The output is reading ~0.02v constant. I trimmed Q2 to be half of Q3 ~22v. Both PS are putting out 49v. There was/is no burning smell or smoke.
Also I have attached the signal gnd to the chassis via a thermistor as has been discussed in other threads. With this attached I was getting different resistance readings from all over the board to chassis. I was not sure if this was good or correct. I removed the attachment and that was the point.
Any help would be fantastic but go easy I am new.
Kris
I am posting to this thread to see if anyone can help me with my Zv9. I got it all together and only one channel is working. The one that is not working is still getting warm and there is a slight hum from the speaker. The output is reading ~0.02v constant. I trimmed Q2 to be half of Q3 ~22v. Both PS are putting out 49v. There was/is no burning smell or smoke.
Also I have attached the signal gnd to the chassis via a thermistor as has been discussed in other threads. With this attached I was getting different resistance readings from all over the board to chassis. I was not sure if this was good or correct. I removed the attachment and that was the point.
Any help would be fantastic but go easy I am new.
Kris
I think I have checked the board for any shorts and found nothing. Anyone have a wiki on troubleshooting an amp like this? I think I may just measure the voltages all over the board and look for differences. Is that the way to do it?
In what order do you usually check stuff to narrow down the issue? I am getting nothing on the input and very little on the output. I suspect it is the input though because there is some hum coming through the speakers. And in my random testings when I put the probe on a small cap it caused a louder hum from the speaker. This happened both sides so I suspect its normal.
In what order do you usually check stuff to narrow down the issue? I am getting nothing on the input and very little on the output. I suspect it is the input though because there is some hum coming through the speakers. And in my random testings when I put the probe on a small cap it caused a louder hum from the speaker. This happened both sides so I suspect its normal.
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