so, after a LOT of headache from the first aleph3, i got the second chassis built, and its not working!
its the same design (an exact replica) of the one seen at my site
http://www.cowanrg.mesanetworks.net/projects/
and in this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=37345&highlight=aleph3
ive done some minor testing as of now. i was blowing fuses, and im still not sure why. i took the power supply apart, then put it back together, and that's fixed.
i accidentally had Q106 and Q107 wired backwards, that is now fixed.
right now, the power supply is good. im getting a nice +-26.66V from the caps. however, im getting almost no draw from the amp. i think i measured the + rail at 0.025A at idle. way too low. my other amp draws 1.88A (its an RMS meter, so that is right on).
the LED doesn't even come on, the fets dont get hot. i have yet to make any board measurements, but with the draw so low, i dont know if it would tell me anything... the only thing i can really tell about the board is that Q103 is getting hot. i left it on for a little bit, and it was quite warm, and everything else was cold.
any simple ideas? if not, ill just have to take it all apart
its the same design (an exact replica) of the one seen at my site
http://www.cowanrg.mesanetworks.net/projects/
and in this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=37345&highlight=aleph3
ive done some minor testing as of now. i was blowing fuses, and im still not sure why. i took the power supply apart, then put it back together, and that's fixed.
i accidentally had Q106 and Q107 wired backwards, that is now fixed.
right now, the power supply is good. im getting a nice +-26.66V from the caps. however, im getting almost no draw from the amp. i think i measured the + rail at 0.025A at idle. way too low. my other amp draws 1.88A (its an RMS meter, so that is right on).
the LED doesn't even come on, the fets dont get hot. i have yet to make any board measurements, but with the draw so low, i dont know if it would tell me anything... the only thing i can really tell about the board is that Q103 is getting hot. i left it on for a little bit, and it was quite warm, and everything else was cold.
any simple ideas? if not, ill just have to take it all apart
wow, i got some really neat readings...
first off, i followed Mike's advice and tested this amp against the working one.
to answer eLarson first, i am not getting any shorts on the fets. they seem ok i guess.
MikeW told me to measure voltage across Q101, Q102, and Q103. here is what i got on my first amp: 3.6, 3.5, and 3.5. a little low, but fine i guess. on the bad amp i get: 3.3, 52, 26.
(on the second transistor, reading on G was ~26v, and on S was -26v, so summed at 52v. on the third, it was 0v on G, and -26v on S).
so, there is definately something wrong there. do i replace Q102 and Q103? or is something else causing the error?
first off, i followed Mike's advice and tested this amp against the working one.
to answer eLarson first, i am not getting any shorts on the fets. they seem ok i guess.
MikeW told me to measure voltage across Q101, Q102, and Q103. here is what i got on my first amp: 3.6, 3.5, and 3.5. a little low, but fine i guess. on the bad amp i get: 3.3, 52, 26.
(on the second transistor, reading on G was ~26v, and on S was -26v, so summed at 52v. on the third, it was 0v on G, and -26v on S).
so, there is definately something wrong there. do i replace Q102 and Q103? or is something else causing the error?
wow.
i measured some resistors. across R108, R106, and Q105. all measurements were nothing! i got a 0v drop across them.
SO, power just isnt getting in. however, im measuring a 0.024A draw across the negative rail. so, power IS connected right, the caps are charging, so i would assume the power supply is ok. (i made measurements at each bridge, and each rail, all are fine).
oh, and i get ~26v or so at the component, so power is running through the board.
i measured some resistors. across R108, R106, and Q105. all measurements were nothing! i got a 0v drop across them.
SO, power just isnt getting in. however, im measuring a 0.024A draw across the negative rail. so, power IS connected right, the caps are charging, so i would assume the power supply is ok. (i made measurements at each bridge, and each rail, all are fine).
oh, and i get ~26v or so at the component, so power is running through the board.
Looks like you are getting rail voltage on your FETS.
Your 3watt resistors probably got burned. Thus probably taking
out their corisponding FETS.
Yank 1 of the fets and test it to see if it's still good.
If it's bad you gotta find out why that happened.
Maybe a bad solder.
Replace the FETS and R's and try again.
just my quick thoughts.
Your 3watt resistors probably got burned. Thus probably taking
out their corisponding FETS.
Yank 1 of the fets and test it to see if it's still good.
If it's bad you gotta find out why that happened.
Maybe a bad solder.
Replace the FETS and R's and try again.
just my quick thoughts.
OK....to test a mosfet
First use ohmmeter to see drain to source is not shorted
Second test... for N channel...connect drain and gate to pos terminal on 12v battery, and source to 10 to 100 ohm resistor to neg terminal. voltage from gate to source should read 3 to 5 volts.
For P channel, reverse polarity on resistor.
First use ohmmeter to see drain to source is not shorted
Second test... for N channel...connect drain and gate to pos terminal on 12v battery, and source to 10 to 100 ohm resistor to neg terminal. voltage from gate to source should read 3 to 5 volts.
For P channel, reverse polarity on resistor.
thank you everyone, especially MikeW. i have fixed the problem! it was a bad diff pair. i replaced them (thankfully i have this crap laying around), and all seems to work. i get the right voltage drops, etc...
still too soon to say its perfect, but we will see. i think both of them can have their bias increased, as they run pretty cool actually. they ran HOT when they were malfunctioning, but now they run pretty cool. just warm to the touch. ill see how hot they get after a couple hours, and then see if i can even remove R113.
still too soon to say its perfect, but we will see. i think both of them can have their bias increased, as they run pretty cool actually. they ran HOT when they were malfunctioning, but now they run pretty cool. just warm to the touch. ill see how hot they get after a couple hours, and then see if i can even remove R113.
Cowanrg,
To make things easier on yourself you really are going to have to
match your FETS when you build the Aleph 2's. It's improtant that
you have good matching of your sets of 6.
How close are your FETS on the Aleph 3? Just measure the Vgs
of each fet on the gain side and the constant current side. Good
close matching is mandatory.
Congrats, Now... on the the 2's 
m.
To make things easier on yourself you really are going to have to
match your FETS when you build the Aleph 2's. It's improtant that
you have good matching of your sets of 6.
How close are your FETS on the Aleph 3? Just measure the Vgs
of each fet on the gain side and the constant current side. Good
close matching is mandatory.
Congrats, Now... on the the 2's
m.
the fets are matched...
i bought like 10 sets of matched fets when i started the 2's. all the fets i used are matched, i have bags of matched fets
however, not time for congratulations yet... im still getting a crappy buzz/hum. im also getting some static-like crap coming through. i guess i need to figure that out. i thought i had it solved when i added the steel plates for isolation. ill try floating the ground or doing something with that, or using another outlet, etc...
if anyone has any ideas, i would appreciate it!
i bought like 10 sets of matched fets when i started the 2's. all the fets i used are matched, i have bags of matched fets
however, not time for congratulations yet... im still getting a crappy buzz/hum. im also getting some static-like crap coming through. i guess i need to figure that out. i thought i had it solved when i added the steel plates for isolation. ill try floating the ground or doing something with that, or using another outlet, etc...
if anyone has any ideas, i would appreciate it!
well, the solder joints seem ok.
i kinda reworked the grounds, but to no avail. i actually floated the earth ground, and it stops the humming at the inputs.
however, im still getting a buzz from the speakers. it happens when no source is connected, just having the amp on, and the speakers connected. i cant tell what frequency, but it comes through the tweeters (when connected to just the tweeters). and it doesnt go away with music, or change in volume.
i hooked up my meter, but i cant get any real reading off of it. i DID however see that at idle, im getting a 7mv offset (pretty decent), and 0.02VAC at idle, without an input. im not sure if this should be 0 or not, but there is definately a bit of power getting through.
i would normally not care about a slight buzz, but my speakers are usually completely silent, even up to 0 on the pre-amp. i never get a hum, buzz or anything, no matter how loud it is. and, you can hear it beyond 2 inches away. you can hear it a few feet away if its quiet enough in the room.
i read a lot concerning grounds, grounding techniques, and such. i seem to be doing everything ok. however, im curious whether or not its a ground issue? can a ground hum (60hz) come through a tweeter?
is there a simple filter that i could use to get rid of the buzz? i have ruled out dirty power as well. i have used it on many different circuits, and its the same on all.
please please help. im really getting discouraged about all this! it seems that as soon as i solve one problem, another one pops up!
i kinda reworked the grounds, but to no avail. i actually floated the earth ground, and it stops the humming at the inputs.
however, im still getting a buzz from the speakers. it happens when no source is connected, just having the amp on, and the speakers connected. i cant tell what frequency, but it comes through the tweeters (when connected to just the tweeters). and it doesnt go away with music, or change in volume.
i hooked up my meter, but i cant get any real reading off of it. i DID however see that at idle, im getting a 7mv offset (pretty decent), and 0.02VAC at idle, without an input. im not sure if this should be 0 or not, but there is definately a bit of power getting through.
i would normally not care about a slight buzz, but my speakers are usually completely silent, even up to 0 on the pre-amp. i never get a hum, buzz or anything, no matter how loud it is. and, you can hear it beyond 2 inches away. you can hear it a few feet away if its quiet enough in the room.
i read a lot concerning grounds, grounding techniques, and such. i seem to be doing everything ok. however, im curious whether or not its a ground issue? can a ground hum (60hz) come through a tweeter?
is there a simple filter that i could use to get rid of the buzz? i have ruled out dirty power as well. i have used it on many different circuits, and its the same on all.
please please help. im really getting discouraged about all this! it seems that as soon as i solve one problem, another one pops up!
wow, you hear something new every day!
i am using kristijan's boards, and they have a 1nf cap on Q104, but nothing on Q105... (you can see it here: http://web.vip.hr/pcb-design.vip/aleph-3.html)
i can try that when i get home. i hope that works. im almost to the point that im gonna give one of my faceplates to whoever can figure it out.
i am using kristijan's boards, and they have a 1nf cap on Q104, but nothing on Q105... (you can see it here: http://web.vip.hr/pcb-design.vip/aleph-3.html)
i can try that when i get home. i hope that works. im almost to the point that im gonna give one of my faceplates to whoever can figure it out.
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