Hi all, my first post is a plea for help.
I put together a single channel of a stereo setup yesterday but seem to have vary strange behavior. I have a steady 26 v input to the board but the R7 and R8 voltages are off the mark. R7 only shows about 2.7 V and R8 about 4.3 V. The voltages across the Q7 and 8 are also very low. Also intermittently the R8 voltage returns to nominal for no conceivable reason.
I've touched up all the soldering and can't see any loose connections and begining to suspect I fried Q3 or Z1.
Any advise is much appreciated.
Thanks
I put together a single channel of a stereo setup yesterday but seem to have vary strange behavior. I have a steady 26 v input to the board but the R7 and R8 voltages are off the mark. R7 only shows about 2.7 V and R8 about 4.3 V. The voltages across the Q7 and 8 are also very low. Also intermittently the R8 voltage returns to nominal for no conceivable reason.
I've touched up all the soldering and can't see any loose connections and begining to suspect I fried Q3 or Z1.
Any advise is much appreciated.
Thanks
Dope, Me not so bright.
Fixing the grounding seem to fix some of the the voltages. I connected earth ground to CL60 to power supply negative and signal ground. The voltage across R7 and 8 are 5 and 8.3 V. The voltages across Q5 and 6 are 4.3 V and voltage across Q7 and 8 are 4.5 V. The voltages across the R16, 17, 18, and 19 is 0.5 V with the power supply doping to 23 V under load.
But the problem is the voltage across the ground and output is 5.4 So I'm still not close to the end.
Any suggestions ?
Thanks
Fixing the grounding seem to fix some of the the voltages. I connected earth ground to CL60 to power supply negative and signal ground. The voltage across R7 and 8 are 5 and 8.3 V. The voltages across Q5 and 6 are 4.3 V and voltage across Q7 and 8 are 4.5 V. The voltages across the R16, 17, 18, and 19 is 0.5 V with the power supply doping to 23 V under load.
But the problem is the voltage across the ground and output is 5.4 So I'm still not close to the end.
Any suggestions ?
Thanks
High Bob, et.al.
I am now looking at which solder to buy because some of my components have low temperature(200Celcius- I have to check this because it is very low) & time limit(2seconds) threshold before heat damage. Dose it matter if the solder has lead in it because all of the ones without lead have a common melting point of 221Celcius, however, I have found one with melting points of 179Celcius but has a bit temperature of 299Celcius. http://www.farnell.com/datasheets/312832.pdf
I know nothing about what I should be looking for in solder, melting point ? silver ?
gold ? Cobalt? Copper? lead? tin? type of resin core? Can you suggest something ?
Thank You all for your comments, it helps keeping me motivated.
Ian Scaiff(scatterbrain001)
I am now looking at which solder to buy because some of my components have low temperature(200Celcius- I have to check this because it is very low) & time limit(2seconds) threshold before heat damage. Dose it matter if the solder has lead in it because all of the ones without lead have a common melting point of 221Celcius, however, I have found one with melting points of 179Celcius but has a bit temperature of 299Celcius. http://www.farnell.com/datasheets/312832.pdf
I know nothing about what I should be looking for in solder, melting point ? silver ?
gold ? Cobalt? Copper? lead? tin? type of resin core? Can you suggest something ?
Thank You all for your comments, it helps keeping me motivated.
Ian Scaiff(scatterbrain001)
Ian,
I use good old 60/40 rosin core solder. Not environmentally friendly but easy to work with. I bought a couple pounds of .032 diameter Alpha Metals solder a while back when the lead free thing started.
I've heard many people like the Cardas Quad Eutectic solder Cardas Audio. Apparently all metals in it solidify at a common temperature making it harder to get a "cold" joint. I haven't tried it though.
I use good old 60/40 rosin core solder. Not environmentally friendly but easy to work with. I bought a couple pounds of .032 diameter Alpha Metals solder a while back when the lead free thing started.
I've heard many people like the Cardas Quad Eutectic solder Cardas Audio. Apparently all metals in it solidify at a common temperature making it harder to get a "cold" joint. I haven't tried it though.
Goober, you adjust R8 to adjust input pair current.
However, now that I look at the schematic, I see that you the left side of the differential is drawing higher than expected current. Before adjusting anything:
Is the offset from output to ground positive or negative? With 5V on R7 I would expect negative.
Are you using a 2SJ109 or a pair of 2SJ74s? If 2SJ74s, did you match them? Are they thermally tied together? Are they protected from breezes when you measure?
What was the Vgs on Q7 and Q8 when you matched them?
Balance or unbalanced input? If unbalanced, is the negative input grounded?
However, now that I look at the schematic, I see that you the left side of the differential is drawing higher than expected current. Before adjusting anything:
Is the offset from output to ground positive or negative? With 5V on R7 I would expect negative.
Are you using a 2SJ109 or a pair of 2SJ74s? If 2SJ74s, did you match them? Are they thermally tied together? Are they protected from breezes when you measure?
What was the Vgs on Q7 and Q8 when you matched them?
Balance or unbalanced input? If unbalanced, is the negative input grounded?
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Hi Bob
I remeasured the off set from output to ground and it is positive. I'm using two 2sj74-bl I sourced from a guy on the forum and he said he match both pairs to about 10.7. Each is sitting
on it's own and there is no heat coming out of them. The gate to source voltage is +4.3V. I got the IRFP240PbF from TechDiy as match 4s and are supposed to be match to +/-0.01.
Thanks for the time.
I remeasured the off set from output to ground and it is positive. I'm using two 2sj74-bl I sourced from a guy on the forum and he said he match both pairs to about 10.7. Each is sitting
on it's own and there is no heat coming out of them. The gate to source voltage is +4.3V. I got the IRFP240PbF from TechDiy as match 4s and are supposed to be match to +/-0.01.
Thanks for the time.
You won't notice much heat out of the input pair, but ideally they are thermally connected to minimize differential thermal effects. Even a small breeze can impact the offset.
Double check resistor values. You can't accurately measure in circuit, so you'll have to read the color codes or lift one end to measure.
If you don't find any bad values, the fun begins. The output stage seems to be generally working properly since you have a pretty well matched 1A in each device. You'll need to verify the input pair matching. That means pulling the Jfets and setting up a matching jig. Ideally, you'll duplicate the CCS and put a 1K resistor on the drain of each device with a 221K resistor from each gate to ground. Use your main power supply. With Peter's boards, I think you can use the x center section as a jig, you'll need to connect Drain resistors to the negative supply since these are on the output boards. Measure the voltage across the Drain load resistors
You can also ground both inputs, and temporarily jumper C1. Lift one end of R25 to turn off the output stage. Assuming R7 and R8 are really both 1K, the voltage on R7 should be exactly half of the voltage on R8 if the devices match. (I think NP meant to show 8.6V on R8)
Let us know what you find.
Double check resistor values. You can't accurately measure in circuit, so you'll have to read the color codes or lift one end to measure.
If you don't find any bad values, the fun begins. The output stage seems to be generally working properly since you have a pretty well matched 1A in each device. You'll need to verify the input pair matching. That means pulling the Jfets and setting up a matching jig. Ideally, you'll duplicate the CCS and put a 1K resistor on the drain of each device with a 221K resistor from each gate to ground. Use your main power supply. With Peter's boards, I think you can use the x center section as a jig, you'll need to connect Drain resistors to the negative supply since these are on the output boards. Measure the voltage across the Drain load resistors
You can also ground both inputs, and temporarily jumper C1. Lift one end of R25 to turn off the output stage. Assuming R7 and R8 are really both 1K, the voltage on R7 should be exactly half of the voltage on R8 if the devices match. (I think NP meant to show 8.6V on R8)
Let us know what you find.
Aleph J-X Input Impedance
High Bob, et. al.
I have looked this over, thank you for this because I would of made a error and only applied the passive xover (PLLC) components to the positive input. I am not shure if I am correct, but I have for the ballanced input, the positive & negative Input Impedance for the Aleph J-X as the same R1+R2 ? Can the Aleph J-X be set up for a non-ballanced input ?
Thank You for your input, I have ordered the 2000+ Soldering Station, with the Fan because I will be useing Sn+Pb+Ag+Cu 179degree Celcius melting point based solder,due to the sensitive State Of The Art components I have purchased, I dont know if this Fan will help though with the solder fumes.
Thank You
Ian Scaiff(scatterbrain001)
I am sorting my currently recieved components now, seporating my Military Equipment Components from my Medical Equipment Components, I believe the medical standard components to be my first choice, and then the Military Components to be my second choice, or then the best sized for the psb(s).
High Bob, et. al.
I have looked this over, thank you for this because I would of made a error and only applied the passive xover (PLLC) components to the positive input. I am not shure if I am correct, but I have for the ballanced input, the positive & negative Input Impedance for the Aleph J-X as the same R1+R2 ? Can the Aleph J-X be set up for a non-ballanced input ?
Thank You for your input, I have ordered the 2000+ Soldering Station, with the Fan because I will be useing Sn+Pb+Ag+Cu 179degree Celcius melting point based solder,due to the sensitive State Of The Art components I have purchased, I dont know if this Fan will help though with the solder fumes.
Thank You
Ian Scaiff(scatterbrain001)
I am sorting my currently recieved components now, seporating my Military Equipment Components from my Medical Equipment Components, I believe the medical standard components to be my first choice, and then the Military Components to be my second choice, or then the best sized for the psb(s).
Choky showed us that the input impedance is R1 (unbalanced by grounding the negative input) http://www.diyaudio.com/forums/pass-labs/145387-aleph-j-x-amp-project-48.html#post2301934
Balanced input impedance is 2xR1, since the negative input impedance is also R1. For balanced input, make two filters based on input impedance = R1.
Balanced input impedance is 2xR1, since the negative input impedance is also R1. For balanced input, make two filters based on input impedance = R1.
Hi Bob
I followed the second method by disconnecting R25, jumpering C1, and shorting the input to ground. The voltages across R8 is 8.5 V but R7 0.2 nowhere close to half. Both R7 and 8 have 1 K printed on them.
I also measured the voltages on the 2SJ74 s, the one connected to R4 has the same 0.2 V between drain and source and gate and source. The other 2SJ74 is at 0 V.
Thank you
I followed the second method by disconnecting R25, jumpering C1, and shorting the input to ground. The voltages across R8 is 8.5 V but R7 0.2 nowhere close to half. Both R7 and 8 have 1 K printed on them.
I also measured the voltages on the 2SJ74 s, the one connected to R4 has the same 0.2 V between drain and source and gate and source. The other 2SJ74 is at 0 V.
Thank you