Hello Aleph builder club!
I have trouble bringing my just finished aleph 5 to live.
When connected to power I can meassure almost no bias current. Additionally I have full positive rail voltage at the output!
Thank god I didn´t connect a speaker.
Something must have gone completely wrong here!
Could zeners with too lower power rating be the reason? I used the smallest types (500 mW I guess) and empoly KRISTIJAN´s A5 boards. All Fets were tested before soldering.
Any help /opinion is greatly appreciated. Thanks in advance!
😕
Franz
I have trouble bringing my just finished aleph 5 to live.
When connected to power I can meassure almost no bias current. Additionally I have full positive rail voltage at the output!
Thank god I didn´t connect a speaker.
Something must have gone completely wrong here!
Could zeners with too lower power rating be the reason? I used the smallest types (500 mW I guess) and empoly KRISTIJAN´s A5 boards. All Fets were tested before soldering.
Any help /opinion is greatly appreciated. Thanks in advance!
😕
Franz
Hi Franz
I would start measuring the voltages as listed in the original schematic: 4-5V across R11, 9V across the Z5, 4-5V across Q5.
Maybe you can give us some more details.
/Hugo - Knows how it feels when things don't work
I would start measuring the voltages as listed in the original schematic: 4-5V across R11, 9V across the Z5, 4-5V across Q5.
Maybe you can give us some more details.
/Hugo - Knows how it feels when things don't work
My first post.
My experience told me that if I encountered problems such as yours, what I need was just a refreshing moment. I would get out or continue on the next day, and would find out that it was just a simple silly mistake.
Based on the experience, I expected you to have answered your own question. But may be the situation is diferent! Then you may need to give exact data for others to assist you solve the problem. You said you measured + rail on the output? Did you mean a "shortage" between Drain and Source of the signal MOSFET? Or else?
My experience told me that if I encountered problems such as yours, what I need was just a refreshing moment. I would get out or continue on the next day, and would find out that it was just a simple silly mistake.
Based on the experience, I expected you to have answered your own question. But may be the situation is diferent! Then you may need to give exact data for others to assist you solve the problem. You said you measured + rail on the output? Did you mean a "shortage" between Drain and Source of the signal MOSFET? Or else?
Sit back and relax, then go to work 😉
First of all check the orientations of Q1 to Q5. Take a look on PSU to A5 PCB wire connection, then check the voltage ratings on all transistors.
Aleph 5 works fine - there must be your error why doesn't work 😎
After this test send us more information.
best regards,
LEON
First of all check the orientations of Q1 to Q5. Take a look on PSU to A5 PCB wire connection, then check the voltage ratings on all transistors.
Aleph 5 works fine - there must be your error why doesn't work 😎
After this test send us more information.
best regards,
LEON
Hello Mr.Stolz,
The power rating of the zener diode could be even 500 mW, and this is
not the reason that your amplifier did not worked from the beginning.
It is 99 % probably an human error during construction,
and not part defect.
Also, there can be a numerous reasons why it comes to the point that
amplifier refuses to work.
When soldering any mosfet tranzistor, you should do that with the soldering iron
grounded, just in any case to avoid static electricity that can damage the
mosfets.
Also, do not heat the transistors and diodes more than required.
You should check for the correct diode orientation, and check the all
resistors and diodes with the Multimeter.
In some cases some colors can look like very similar and it is very
difficult to tell which one it is, especially on the metal-film types.
Check that the all transistors are electricaly isolated from their
heatsinks.
Also, if you have any higher voltage at the output (like very high offset),
you should desolder all the transistors and then check each one separately
for their proper operation.
Before another power up, check the power supply for the right voltages.
Before any first power up try to check everything several times,
no matter how long it would take and how that is boring, at the end it can
save you a lot's of your time and nervs.
Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip
The power rating of the zener diode could be even 500 mW, and this is
not the reason that your amplifier did not worked from the beginning.
It is 99 % probably an human error during construction,
and not part defect.
Also, there can be a numerous reasons why it comes to the point that
amplifier refuses to work.
When soldering any mosfet tranzistor, you should do that with the soldering iron
grounded, just in any case to avoid static electricity that can damage the
mosfets.
Also, do not heat the transistors and diodes more than required.
You should check for the correct diode orientation, and check the all
resistors and diodes with the Multimeter.
In some cases some colors can look like very similar and it is very
difficult to tell which one it is, especially on the metal-film types.
Check that the all transistors are electricaly isolated from their
heatsinks.
Also, if you have any higher voltage at the output (like very high offset),
you should desolder all the transistors and then check each one separately
for their proper operation.
Before another power up, check the power supply for the right voltages.
Before any first power up try to check everything several times,
no matter how long it would take and how that is boring, at the end it can
save you a lot's of your time and nervs.
Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip
my fault
I had once the same thing
Reason: reverse positioned zenerdiode in the diff. current source.
Leads to no current in diff pair -> no current in output devices
-> maximum positive voltage on output!
Turn this zener!
Uli
Franz said:
I had once the same thing
Reason: reverse positioned zenerdiode in the diff. current source.
Leads to no current in diff pair -> no current in output devices
-> maximum positive voltage on output!
Turn this zener!
Uli
failiure still unknown
Hello all
thanks for your help so far but I still have no clue.
I checked diode polarity several times, everythink o.k. and according to PCB printing. All zeners have near identical voltage in conducting direction when meassured with DMM.
Could have been such a nice easy solution if only one had been reversed.
I also checked for shorts on the solder side of the board and found nothing.
I measured DC at output again and it is +32,5 V with 36 V at the rails.
I have no voltage across the 392 R resistor (should be 4-5 V says Nelson)
My only guess left is that input devices Q 1-3 are bad, although I tetsed them all while selection.
So solder them all out ? Any more ideas?
Thanks again and have a nice weekend
Franz😕 😕
Hello all
thanks for your help so far but I still have no clue.
I checked diode polarity several times, everythink o.k. and according to PCB printing. All zeners have near identical voltage in conducting direction when meassured with DMM.
Could have been such a nice easy solution if only one had been reversed.
I also checked for shorts on the solder side of the board and found nothing.
I measured DC at output again and it is +32,5 V with 36 V at the rails.
I have no voltage across the 392 R resistor (should be 4-5 V says Nelson)
My only guess left is that input devices Q 1-3 are bad, although I tetsed them all while selection.
So solder them all out ? Any more ideas?
Thanks again and have a nice weekend
Franz😕 😕
diff pair
Hi Franz,
no voltage across 392R means no current thru the according
half of the diff pair.
Look at the current source which drives the sources (about +4V)
of the diff pair. In this CCS the resistor (221R) from source to +V should have about 5 - 5.3 V -> ~20mA. with 9.1V between gate and +V. If not then theres something wrong with the CCS!
Control the voltages at the gates of the diff pair.
Interchange the diff pair and look what happens.
1) +V on output -> CCS bad.
2) - V on output -> Diff Pair bad.
Uli
Hi Franz,
no voltage across 392R means no current thru the according
half of the diff pair.
Look at the current source which drives the sources (about +4V)
of the diff pair. In this CCS the resistor (221R) from source to +V should have about 5 - 5.3 V -> ~20mA. with 9.1V between gate and +V. If not then theres something wrong with the CCS!
Control the voltages at the gates of the diff pair.
Interchange the diff pair and look what happens.
1) +V on output -> CCS bad.
2) - V on output -> Diff Pair bad.
Uli
In your situation, this is what I'm gonna do:
1. In the IRF9610 current source, check the voltage across zener. It should be 9V (the rest, 36V-9V, will be handled by the 1W resistor)
2. Pull out the differential pairs (IRF9610)
3. Check the current flowing through the Drain of IRF9610 current source. I think it is about 30mA (or 15mA to each half of diff pairs in a working circuit)
4. Check each of the pulled IRF9610 (using multimeter). Are they broken?
1. In the IRF9610 current source, check the voltage across zener. It should be 9V (the rest, 36V-9V, will be handled by the 1W resistor)
2. Pull out the differential pairs (IRF9610)
3. Check the current flowing through the Drain of IRF9610 current source. I think it is about 30mA (or 15mA to each half of diff pairs in a working circuit)
4. Check each of the pulled IRF9610 (using multimeter). Are they broken?
Hello all my helpers!
yesterday I pulled Q3 (current source) and its VGS was quite normal. Is there any other indicator to see that Fets are o.k. or not?
I measured VGS of Q1 and Q2 on board (!) and they seemed to be o.k. as well.
Voltage across Z5 at current source is only about 7 V and not 9 V as it should be. That´s strange !!
Any more ideas?
Thanx
Franz😕 🙁
yesterday I pulled Q3 (current source) and its VGS was quite normal. Is there any other indicator to see that Fets are o.k. or not?
I measured VGS of Q1 and Q2 on board (!) and they seemed to be o.k. as well.
Voltage across Z5 at current source is only about 7 V and not 9 V as it should be. That´s strange !!
Any more ideas?
Thanx
Franz😕 🙁
bug found!
Hi there!
That was a hard one!!
One trace on the pc board was almost interrupted. A very tiny hair-like piece was left over that caused a heavy voltage drop so that only 3 V arrived at the current source zener diode Z5.
It was hardly visible underneath the laquer.
This kind of failure should really not occur with readymade "pro"-boards by PCB design!! Watch your QC Kristijan!!
Almost everything seeems to work fine now , I only have a litte high DC offset which climbs to about 70 mV.
Also its strange that I get about 2,5 V offset after turning off power. Is that normal?
What could be the reason?
Again, thanks for all your input folks.
Franz
Hi there!
That was a hard one!!
One trace on the pc board was almost interrupted. A very tiny hair-like piece was left over that caused a heavy voltage drop so that only 3 V arrived at the current source zener diode Z5.
It was hardly visible underneath the laquer.
This kind of failure should really not occur with readymade "pro"-boards by PCB design!! Watch your QC Kristijan!!
Almost everything seeems to work fine now , I only have a litte high DC offset which climbs to about 70 mV.
Also its strange that I get about 2,5 V offset after turning off power. Is that normal?
What could be the reason?
Again, thanks for all your input folks.
Franz
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