flq,
Did you know your moniker is the same as a terrorist group that was active in Quebec, Canada in the 1970's? I'm showing my age.
I was interested in your point above. Can you be more specific about how to test the Gate to source/drain. Exactly where do I place the probes? How do I know the leakage? TIA, Fred
Did you know your moniker is the same as a terrorist group that was active in Quebec, Canada in the 1970's? I'm showing my age.
I was interested in your point above. Can you be more specific about how to test the Gate to source/drain. Exactly where do I place the probes? How do I know the leakage? TIA, Fred
Gate to Source and Gate to Drain are diode like. With no power they shoudl show conduction in one direction, but open in the other. Use your DMM in resistance mode (or diode mode if you have it), and check for resistance between the pins. You should see infinite resistance in one direction, and some conduction in the other.
cfbuck, Nope, did not know about that group... I like to build things, obviously, and most of what ever leaves the house was created in the garage. Not everything... But, after a while, I figured I should at least sign it or put my name on it or something... flg means, found in Lee's garage 😀 😀 😀
Age??? I was a teenager in the 70's 😀
Yes , well I've fixed a few amps in my time, junk mostly but, this noise thing I think it was described as a slightly lower freq and varying, or something. Hush? That sounds like more than the typical low level Hisss to me... At first I would check caps but, the author said, since it was new??? Maybe not a cap??? Well, partially blown up transistors allow some leakage that generally sounds like the description to me. It would normally be serious crakling or somthing though and you would not conitue using it.
However, If we were talking about an IRF610 or somthing, I would put my handy multimeter on Ohms and go + on the drain and - on the source and the reading will be very high. My handheld probably would indicate an open, ???megaohms... If it is seriously smoked You would see it with that test... If your + and - are reversed you may be seeing the foward current of a diode with some FETs... However, I would go on to put the + on the Gate and the - on the source and again, open... Then just move the - to the source and again, you would expect an open... A better meter, with higher input impeadance may actually measure something but, you should not see any values much below a megohm. A big FET may be lower, and you may see the gate capacitance for a short time but it will instantly go to a very high number... Another good test is to compare a few, on the assumption that they are not all blown up... I have seen what I thought was the same phenomina but only at higher voltages than a meter set to ohms. In that case a scope will see garbagy looking spikeing stuff.
However,(just one more), I do not disagree with one other member who suggested the bias may be abnormally low. I've run my BOSOZ type cicuits anywhere from 50 to 95mA so I'm not sure how bad it gets when your only running a few mA's. I also like to use a lttle more Voltage than N.P.'s cicuits. Yes, I use a good size heat sink for that😀 😀 😀
Like I need to say more??? After Brians post... It sounds like he is describing a BJT(regular ol BiPolar transistor). Most of the stuff I play with has 20Volts worth of oxide between the gate and anything else. Meaning 0.0 dc current will pass. As I suggested tjhough, the IRF610 is one of those pasrts with a built in diode which can be seen with + on the source and - on the drain...
Age??? I was a teenager in the 70's 😀
Yes , well I've fixed a few amps in my time, junk mostly but, this noise thing I think it was described as a slightly lower freq and varying, or something. Hush? That sounds like more than the typical low level Hisss to me... At first I would check caps but, the author said, since it was new??? Maybe not a cap??? Well, partially blown up transistors allow some leakage that generally sounds like the description to me. It would normally be serious crakling or somthing though and you would not conitue using it.
However, If we were talking about an IRF610 or somthing, I would put my handy multimeter on Ohms and go + on the drain and - on the source and the reading will be very high. My handheld probably would indicate an open, ???megaohms... If it is seriously smoked You would see it with that test... If your + and - are reversed you may be seeing the foward current of a diode with some FETs... However, I would go on to put the + on the Gate and the - on the source and again, open... Then just move the - to the source and again, you would expect an open... A better meter, with higher input impeadance may actually measure something but, you should not see any values much below a megohm. A big FET may be lower, and you may see the gate capacitance for a short time but it will instantly go to a very high number... Another good test is to compare a few, on the assumption that they are not all blown up... I have seen what I thought was the same phenomina but only at higher voltages than a meter set to ohms. In that case a scope will see garbagy looking spikeing stuff.
However,(just one more), I do not disagree with one other member who suggested the bias may be abnormally low. I've run my BOSOZ type cicuits anywhere from 50 to 95mA so I'm not sure how bad it gets when your only running a few mA's. I also like to use a lttle more Voltage than N.P.'s cicuits. Yes, I use a good size heat sink for that😀 😀 😀
Like I need to say more??? After Brians post... It sounds like he is describing a BJT(regular ol BiPolar transistor). Most of the stuff I play with has 20Volts worth of oxide between the gate and anything else. Meaning 0.0 dc current will pass. As I suggested tjhough, the IRF610 is one of those pasrts with a built in diode which can be seen with + on the source and - on the drain...
[B]Everything was fine until one day...[/B]
Desperate X-BOSOZ builder needs help.
Everything in my new X-BOSOZ/JT volume control preamp was working perfectly until yesterday when I made a minor change to the chassis& circuit grounding. Afterwards one channel gave up and I suspect the other channel will follow soon.
The symptoms are similar to the ones described by hayenc in thread #929. On both channels, the output resistors R2/7 get extremely hot with a voltage drop of around 60V (!), while the other pair (R2/6) stays cool. Power supply is OK with +82V and -20 V, and I measured around 2 V drop across R3. the zeners test OK
Any ideas what could be wrong? Did I blow the FETs and how can they be tested in situ?
Thanks for any comments
Alex
Desperate X-BOSOZ builder needs help.
Everything in my new X-BOSOZ/JT volume control preamp was working perfectly until yesterday when I made a minor change to the chassis& circuit grounding. Afterwards one channel gave up and I suspect the other channel will follow soon.
The symptoms are similar to the ones described by hayenc in thread #929. On both channels, the output resistors R2/7 get extremely hot with a voltage drop of around 60V (!), while the other pair (R2/6) stays cool. Power supply is OK with +82V and -20 V, and I measured around 2 V drop across R3. the zeners test OK
Any ideas what could be wrong? Did I blow the FETs and how can they be tested in situ?
Thanks for any comments
Alex
Re: [B]Everything was fine until one day...[/B]
With an interest, I looked at the schematic in post#1.
I wonder why the schematic uses two voltage references (LM4040-10) instead of one which could be common for both the left and right sides. If they have two different reference voltages unfortunately, it could result in the different bias current sharing between the left and the right side.
I also wondering why the gate resistors (220ohms) are omitted from Q2 and Q3.
Regards
1001meier said:
With an interest, I looked at the schematic in post#1.
I wonder why the schematic uses two voltage references (LM4040-10) instead of one which could be common for both the left and right sides. If they have two different reference voltages unfortunately, it could result in the different bias current sharing between the left and the right side.
I also wondering why the gate resistors (220ohms) are omitted from Q2 and Q3.
Regards
Re: Re: [B]Everything was fine until one day...[/B]
http://www.diyaudio.com/forums/showthread.php?postid=909220#post909220
jh6you said:
http://www.diyaudio.com/forums/showthread.php?postid=909220#post909220
Here is the actual schematic, the schmematic in post 1 is just cut. 🙂
Gate resistors and such were added.
http://www.diyaudio.com/forums/showthread.php?postid=908271#post908271
Gate resistors and such were added.
http://www.diyaudio.com/forums/showthread.php?postid=908271#post908271
Re: Re: Re: [B]Everything was fine until one day...[/B]
He he . . . you are another fast car . . .
choky said:
He he . . . you are another fast car . . .
I'm gonna give up. I took a break from by bosoz since I was having trouble to build The Krell. Glad I did, it's a nice addition.
One channel of the bosoz is gonna start causing hair loss. Let me start by saying it's not the psu...works fine on the other channel.
I am in the situation where when I measure between the inputs (fet sides) of the output caps on either side of the board I have voltage...varying voltage between 2.5v and about 12v. It starts not too bad but slowly climbs till it rests at a too high number. The good board starts good and stays good. VGS on all corresponding fets are virtually identical.(i.e Q2 and Q3 match each other, Q4 and Q5 match each other) All zeners are rock solid, as are the references. Obviously the voltage dropped across the paralleled power resistors (1.5k ones) does not match with the other side, and varies as well and consistent with other variations. (when I say 'side' I mean side of the same board. I'm not comparing to the other working channel. I have tried replacing all fets 3 times now as well as the 1.5k resistors twice.
This board looks like **** now!
There is an imbalance somewhere and I can't find it, any suggestions....?
Thanks
One channel of the bosoz is gonna start causing hair loss. Let me start by saying it's not the psu...works fine on the other channel.
I am in the situation where when I measure between the inputs (fet sides) of the output caps on either side of the board I have voltage...varying voltage between 2.5v and about 12v. It starts not too bad but slowly climbs till it rests at a too high number. The good board starts good and stays good. VGS on all corresponding fets are virtually identical.(i.e Q2 and Q3 match each other, Q4 and Q5 match each other) All zeners are rock solid, as are the references. Obviously the voltage dropped across the paralleled power resistors (1.5k ones) does not match with the other side, and varies as well and consistent with other variations. (when I say 'side' I mean side of the same board. I'm not comparing to the other working channel. I have tried replacing all fets 3 times now as well as the 1.5k resistors twice.
This board looks like **** now!
There is an imbalance somewhere and I can't find it, any suggestions....?
Thanks
Member
Joined 2002
mpmarino said:
Can you show us any pictures ?
Just a note i don't use my X-bosoz much any more.. I now use a simple buffer with some high end black gate caps.. The Bosoz has lots of hush sound..
I checked r values a few times.. didn't check for oscillations. I am probably gonna take another break soon (unless there is a breakthrough quick) on this one so I can start a pair of speaks I wanna build .
In the meantime, who's got a ns10 they wanna sell me for next to nothing🙂
A good phono section has just become paramount for me😀
solved by the atten on the output?
Pictures...are you kidding! It looks exactly like the good channel only WAY uglier. Not the Choky ugly either.
In the meantime, who's got a ns10 they wanna sell me for next to nothing🙂
A good phono section has just become paramount for me😀
solved by the atten on the output?
Pictures...are you kidding! It looks exactly like the good channel only WAY uglier. Not the Choky ugly either.
just desolder everything from PCB ,double check PCB for continuity and shorts,then check each element before soldering again......
you think that repair electronics is easy job ?
I know few other routes,but this one is certainly less confusing than any other,even if it's longest
you think that repair electronics is easy job ?
I know few other routes,but this one is certainly less confusing than any other,even if it's longest
Oh No!
I've already had basically every component out for measurement, although I have not emptied the board as you suggest... a good suggestion at this point. I'm afraid the board will be too damaged if I keep pullin' stuff out, it's getting there.
My play time is limited and I have probably 5 or 6 hours into the board. Too much by my standards and availabilty.
Very hard job🙂
edit: I get the feeling you think it may be a board or solder prob. your probably right. I don't think it's a component, maybe a ghost in the board
mpmarino said:
Oh No!
I've already had basically every component out for measurement, although I have not emptied the board as you suggest...
Mark send me some email. I may have some relief for you... 🙂
mpmarino said:
My play time is limited and I have probably 5 or 6 hours into the board. Too much by my standards and availabilty.
Very hard job🙂
edit: I get the feeling you think it may be a board or solder prob. your probably right. I don't think it's a component, maybe a ghost in the board
hehe
tellmeaboudidt........😉
I'm Chokyfying pair of KK's X Bosoz PCBs in something useful......
say-last iteration of this thread's gadget (somewhere up the thread)...
today I finally make last preparation of heatsinks etc,this days it will be powered........
but working with nice looking,but otherwise crappy PCBs is really another xperience ,not just PITA like in your case ......
Member
Joined 2002
OK so i'm now running the pre-amp non-balanced all rca both in & out. with the pot on the output.. 😀😀😀 Works good now.. Now to remove that little bit of hum that i have..
OK Jase! Now convert those miniA's of yours to balanced input (the boards are already set up to accept balanced) and you'll hear the pre step up to another level.
For the hum, I had to get brutal with the grounding scheme making the connections to the star ground all as low impedance as possible. The good news is that as soon as you switch the pre to balanced out, the hum will go away too.
Cheers,
Terry
For the hum, I had to get brutal with the grounding scheme making the connections to the star ground all as low impedance as possible. The good news is that as soon as you switch the pre to balanced out, the hum will go away too.
Cheers,
Terry
Member
Joined 2002
They are in balanced and RCA mode. If i use the pre amp like this..
Cd player > passive volume pot > Rca in > balanced out > mini A's then i get the hush sound..
It's been recommended to used the balanced pot on the output of the pre-amp in balanced mode. BUT i don't have a balanced pot so i cant. 🙁
Like these 🙂
Cd player > passive volume pot > Rca in > balanced out > mini A's then i get the hush sound..
It's been recommended to used the balanced pot on the output of the pre-amp in balanced mode. BUT i don't have a balanced pot so i cant. 🙁
Like these 🙂
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.
