Hi
My unregulated voltage coming out of the Zen Power Supply (measured across the capacitor) is turning out to be close to 57 V!!! I am using the same Piltron transformer recomended in the Pass Zen V4 article on the pass website. I am measureing this WITHOUT connecting the amp PCB. This is a no load measurement. The question is, is this value too high. I recently blew R0 and R1 on one channel, Is this high voltage causing this?
thanks
vsr
My unregulated voltage coming out of the Zen Power Supply (measured across the capacitor) is turning out to be close to 57 V!!! I am using the same Piltron transformer recomended in the Pass Zen V4 article on the pass website. I am measureing this WITHOUT connecting the amp PCB. This is a no load measurement. The question is, is this value too high. I recently blew R0 and R1 on one channel, Is this high voltage causing this?
thanks
vsr
For Q5 you use IRFP240 right? If Q5 is IRFP044 i can imageine with a little more than 57V it would die.
OK, in case the regulator is wotking it should be no difference for R0 and R1 if power supply delivers 50V or 57V unreg. into Q5 because past regulator there would be ca. 42V in both cases. But with 57V Q5 would be a little more warm... no problem with enough heatsink.
Also this 57V may go down when the transformer is under load, test it.
In case you unsoldiered Q2 and/or Q1 and/or R0/R1 please test the regulator. is there ca. 46V between zehners and R17?
is there ca.42V past Q5? Did you soldier D1 right way, all zehners ok? else there may be more than 42V.
Please measure and post else it will be difficult to locate errors.
OK, in case the regulator is wotking it should be no difference for R0 and R1 if power supply delivers 50V or 57V unreg. into Q5 because past regulator there would be ca. 42V in both cases. But with 57V Q5 would be a little more warm... no problem with enough heatsink.
Also this 57V may go down when the transformer is under load, test it.
In case you unsoldiered Q2 and/or Q1 and/or R0/R1 please test the regulator. is there ca. 46V between zehners and R17?
is there ca.42V past Q5? Did you soldier D1 right way, all zehners ok? else there may be more than 42V.
Please measure and post else it will be difficult to locate errors.
B+ on v4
58 volts sounds a little high, but with Q1 in shut off the voltage will come down once the boards are connected.. I think that with the amp idling at 2 amps you will see about 50 volts on the raw power supply.
I am running a 38v winding instead of series connected 18 volt and get 57 volts with Q1 shut off, and 53v with it running at 1.25 amps.
Check all the connections to the big transistors. the smoking of the resistors across the current source sounds like a lot of current is being pulled across the source.
George
58 volts sounds a little high, but with Q1 in shut off the voltage will come down once the boards are connected.. I think that with the amp idling at 2 amps you will see about 50 volts on the raw power supply.
I am running a 38v winding instead of series connected 18 volt and get 57 volts with Q1 shut off, and 53v with it running at 1.25 amps.
Check all the connections to the big transistors. the smoking of the resistors across the current source sounds like a lot of current is being pulled across the source.
George
Zen V4
Thanks all for your prompt replies. I will post the values soon. I had one question regarding the measurement of values when using a 150W bulb in series with the primary of the transformer. There is a schematic given with the expected values. It gives the unregulated voltage as 23V. Does anyone know whether this is with the R4 adjusted or turned all the way anit-clockwise?
Heres what I have so far -
1. Turned up the circuit with a 150W bulb in series with the primary. The measured voltage across R0 it is constant at about 0.38V. The unregulated voltage measured at the power supply CAP was about 37V.
2. I started adjusting R4 by turning it clockwise. The Voltage across R0 did not change. The voltage across the CAP started coming down all the way to 28V. At this point the voltage across the Q1 drain was about 16 V.
Everything seems ok at this point, no smoke, no smell.
3. I tried turning the R4 further clockwise and started to see the voltage across Q1 rise but also a lot of heat and the solder on the drain of Q1 actually started melting!!!
4. I adjusted the R4 back to what it was to get a Q1 voltage of about 16V. It seems fine here. there is a fair amount of heat from Q1. A quick measurement on the drain of Q1 tells me that the heat is close to 90+C. The heatsink itself is pretty cool. I know that the heatsinks I have were used in an Aleph 2 so 100W should be easy for it.
I used a discman for an input at this point and ran the output to a speaker. The sound seemed nice but I didnt run it long enough in this configuration.
I checked all the zeners, they all worked out.
Questions -
5. Is the 23 V unregulated shown in other web postings measured after adjustment of R4?
6. Is 90+ C very high on the transistor drain?
Next, if these are correct should I go ahead turn up the amp without the bulb? the only scary part so far is the Q1 temperature?
thanks
vsr
Thanks all for your prompt replies. I will post the values soon. I had one question regarding the measurement of values when using a 150W bulb in series with the primary of the transformer. There is a schematic given with the expected values. It gives the unregulated voltage as 23V. Does anyone know whether this is with the R4 adjusted or turned all the way anit-clockwise?
Heres what I have so far -
1. Turned up the circuit with a 150W bulb in series with the primary. The measured voltage across R0 it is constant at about 0.38V. The unregulated voltage measured at the power supply CAP was about 37V.
2. I started adjusting R4 by turning it clockwise. The Voltage across R0 did not change. The voltage across the CAP started coming down all the way to 28V. At this point the voltage across the Q1 drain was about 16 V.
Everything seems ok at this point, no smoke, no smell.
3. I tried turning the R4 further clockwise and started to see the voltage across Q1 rise but also a lot of heat and the solder on the drain of Q1 actually started melting!!!
4. I adjusted the R4 back to what it was to get a Q1 voltage of about 16V. It seems fine here. there is a fair amount of heat from Q1. A quick measurement on the drain of Q1 tells me that the heat is close to 90+C. The heatsink itself is pretty cool. I know that the heatsinks I have were used in an Aleph 2 so 100W should be easy for it.
I used a discman for an input at this point and ran the output to a speaker. The sound seemed nice but I didnt run it long enough in this configuration.
I checked all the zeners, they all worked out.
Questions -
5. Is the 23 V unregulated shown in other web postings measured after adjustment of R4?
6. Is 90+ C very high on the transistor drain?
Next, if these are correct should I go ahead turn up the amp without the bulb? the only scary part so far is the Q1 temperature?
thanks
vsr
melting solder and 90°C sound not so good. Did you use thermal grease (or at least any grease) between FET and heatsink, does the FET sit tight on heasink? try to move it for test.
0.38V (should be 0,5 - 0,66V, maybe use another Q3 )across R0 = 4.47R means about 0,8A
0,8A * 16V or more means about 13W. This should not be much, not enough for 90°c if there is a heatsink mountet correctly.
Also 0,8A should not melt a solder point, if soldered correctly. please check.
Do you have a DMM with option for frequency measurement or a oscilloscope?
could you check for oscillation?
Please make sure every connection is made big enough, low resistance, good soldered etc.
At least, could you post a high resolution picture of both sides of PCB?
For adjustment: As far as i understand it there is an area were you close the Fet, not enough voltage at gate. No currrent, no load for PS. Then you reach 4V or so at gate, Q1 opens and nominal current (1,3A or 2 A or whatever results from R0 and VBE) goes trough Q1, Q2, R0. In this area were Q1 is open current is not affected by adjustemt. But the voltage at drain of Q1. You adjust for 1/2 voltage to reach maximum voltage swing, but amp will work (with less watt until clip) with more or less than1/2V (0.5*42V).
So at the moment i think absolut adjustment of R4 is not important, important is to get the amp working with less temperature at the Fet and no solder melting. For this check heatsink connection (mechanical, termal) and oscillation.
0.38V (should be 0,5 - 0,66V, maybe use another Q3 )across R0 = 4.47R means about 0,8A
0,8A * 16V or more means about 13W. This should not be much, not enough for 90°c if there is a heatsink mountet correctly.
Also 0,8A should not melt a solder point, if soldered correctly. please check.
Do you have a DMM with option for frequency measurement or a oscilloscope?
could you check for oscillation?
Please make sure every connection is made big enough, low resistance, good soldered etc.
At least, could you post a high resolution picture of both sides of PCB?
For adjustment: As far as i understand it there is an area were you close the Fet, not enough voltage at gate. No currrent, no load for PS. Then you reach 4V or so at gate, Q1 opens and nominal current (1,3A or 2 A or whatever results from R0 and VBE) goes trough Q1, Q2, R0. In this area were Q1 is open current is not affected by adjustemt. But the voltage at drain of Q1. You adjust for 1/2 voltage to reach maximum voltage swing, but amp will work (with less watt until clip) with more or less than1/2V (0.5*42V).
So at the moment i think absolut adjustment of R4 is not important, important is to get the amp working with less temperature at the Fet and no solder melting. For this check heatsink connection (mechanical, termal) and oscillation.
Hi Till
I dont think the FET mounting is the problem since I did check to see if I could wiggle it or move it and it is tight. I am using sil pads, so I did not use any thermal grease.
The soldering looks good (has the shine and is a tight connection). I posted a few days back that I blew one channel - that did have bad soldering on there, but for this channel I got another soldering iron and made sure that all connections were tight.
Unfortunately I dont have any way to check for oscillations. If I were to check for oscillation, where would I be checking it?
I dont have a digital camera but will post pitcures as soon as I can get hold of one.
Meanwhile I will try a different heatsink mounting and see if that makes a difference. I am measuring the voltage on Q1 between drain and ground.
thanks again
vsr
I dont think the FET mounting is the problem since I did check to see if I could wiggle it or move it and it is tight. I am using sil pads, so I did not use any thermal grease.
The soldering looks good (has the shine and is a tight connection). I posted a few days back that I blew one channel - that did have bad soldering on there, but for this channel I got another soldering iron and made sure that all connections were tight.
Unfortunately I dont have any way to check for oscillations. If I were to check for oscillation, where would I be checking it?
I dont have a digital camera but will post pitcures as soon as I can get hold of one.
Meanwhile I will try a different heatsink mounting and see if that makes a difference. I am measuring the voltage on Q1 between drain and ground.
thanks again
vsr
ok, just check for oscillation between drain and ground or at speaker output.
Try to borrow somewere at DMM wich can measure frequency.
I don´t think we will find something related to the heatsink in case mounting is ok and heatsink big enough, what you confirmed both.
Is it possible the turn on the amp for longer time with the series lightbulb and adjustment of R4 for a voltage at drain between 5V and 16V, or does it get too hot?
Is your Multimeter able to measure AC and DC voltage? what voltage is there at speaker output (behind the output capacitor) in the both modes?
Try to borrow somewere at DMM wich can measure frequency.
I don´t think we will find something related to the heatsink in case mounting is ok and heatsink big enough, what you confirmed both.
Is it possible the turn on the amp for longer time with the series lightbulb and adjustment of R4 for a voltage at drain between 5V and 16V, or does it get too hot?
Is your Multimeter able to measure AC and DC voltage? what voltage is there at speaker output (behind the output capacitor) in the both modes?
I ran the amp for about 10 minutes at about 16V on Q1 drain. The temperature of drain pin is high but there is no melting of solder or any visual problem. I played about 3 songs and it seems to have ran clean although definitely at lower volume.
When you ask if it is possible to turn the amp on for a longer time at around 16V, how long - 30 mintes? 1 hour? I can try that.
The DMM I have can do both AC and DC voltages. I will take both measurements and port what it works out to.
vsr
When you ask if it is possible to turn the amp on for a longer time at around 16V, how long - 30 mintes? 1 hour? I can try that.
The DMM I have can do both AC and DC voltages. I will take both measurements and port what it works out to.
vsr
ten minutes is good information, this means temperature doesnt run away instantly. lower volume mea´ns it was not too loud, or it got less loud over ten minutes? was there a change in this ten minutes or not?
The question with the DMM is, can it really measure AC, or would it interpret DC in AC mode as voltage too. My DMM for example shows at 10 V DC in AC mode 0V. This means in case there is oscillation at output we would have a hint when it shows voltage in AC mode at speaker connector without signal at input.
What says the temperature of R0 in these ten minutes?
Did you use better wires and connections between power supply and PCB at this ten minutes test that that time it smoked?
In my case everything worked ok, with good connections, with thin crococabels in test setup it oscillated and blew resistors.
Do you use a thermistor in series to transformer primary? I need to use one, else sometimes fuse of power mains trips.
The question with the DMM is, can it really measure AC, or would it interpret DC in AC mode as voltage too. My DMM for example shows at 10 V DC in AC mode 0V. This means in case there is oscillation at output we would have a hint when it shows voltage in AC mode at speaker connector without signal at input.
What says the temperature of R0 in these ten minutes?
Did you use better wires and connections between power supply and PCB at this ten minutes test that that time it smoked?
In my case everything worked ok, with good connections, with thin crococabels in test setup it oscillated and blew resistors.
Do you use a thermistor in series to transformer primary? I need to use one, else sometimes fuse of power mains trips.
The temperature does not seem to run away instantly. I ran it for 10 minutes, no change in volume during those 10 minutes, the sound seemed perfect. I ran it at almost full input volume (headphone output through a discman) and the overall level of sound coming out from the speaker was lower than it would have been with 30 W (I know this since i have a 35W amp at home). You said I was probably operating at about 10W, thats probably true.
The DMM I believe will show zero in AC since I get almost 0 v (or an oscillating reading very close to 0 - more like 0.03 v or so. I will check AC voltage at speaker though, what would a typical value be in the range of?
The DMM I use is capable of measuring temperature (it has a probe on there)....thats what I used to measure the temperature.
The last time I blew a channel I was using bad soldering (loose in some cases) and croc-wires. I changed all that on this channel, used a better soldering iron, all cables are tight - no loose solder, all 16AWG wire throughout. All rectifer circuits are wired using crimp lugs and are tight.
For the mounting of Q1, I can replace with mica and grease just for that transistor and see if there is a difference.
I use a thermistor in series, just as in the manual.
thanks again for all your help...I will post the measurements shortly.
The DMM I believe will show zero in AC since I get almost 0 v (or an oscillating reading very close to 0 - more like 0.03 v or so. I will check AC voltage at speaker though, what would a typical value be in the range of?
The DMM I use is capable of measuring temperature (it has a probe on there)....thats what I used to measure the temperature.
The last time I blew a channel I was using bad soldering (loose in some cases) and croc-wires. I changed all that on this channel, used a better soldering iron, all cables are tight - no loose solder, all 16AWG wire throughout. All rectifer circuits are wired using crimp lugs and are tight.
For the mounting of Q1, I can replace with mica and grease just for that transistor and see if there is a difference.
I use a thermistor in series, just as in the manual.
thanks again for all your help...I will post the measurements shortly.
Measurements
I was using silpads to mount Q1 which was getting as hot as 90 C.
I changed that Q1 mounting to mica and thermal grease, with 10 minutes of running Q1 gets to as hot as 68C (initially 68 and then comes down a bit to 60C) a remarkable difference from 90C. Solder looks good...no melting now
Input unreglated voltage is about 28V (that seems to be the lowest that I can get it to by adjusting R4) - other threads say it has to be 23V?
Voltage across drain is only 16V
Voltage across R0 is now 0.52 V.
Ac and DC voltages across input to speaker is -
AC - varying 0.4V is the peak that I could see
DC - 0 volts.
Temperature of R0 after 15 minutes is approx - 30 C (the heatsink is a little cooler)
One observation is that if I vary R4 from this point (which is about half a turn from full anti-clockwise) either clockwise or anticlockwise the unregualted voltage input changes in the same direction - it goes up to 32V and keeps rising. The Voltage across R0 drops to 0.42V or less (depending on how much I change R4).
So Temperature looks much better on Q1. However the heatsink temperature after running for nearly half an hour is only around 30C !
I still have the bulb in series with the primary. Should I remove it and see what happens?
thanks
vsr
I was using silpads to mount Q1 which was getting as hot as 90 C.
I changed that Q1 mounting to mica and thermal grease, with 10 minutes of running Q1 gets to as hot as 68C (initially 68 and then comes down a bit to 60C) a remarkable difference from 90C. Solder looks good...no melting now
Input unreglated voltage is about 28V (that seems to be the lowest that I can get it to by adjusting R4) - other threads say it has to be 23V?
Voltage across drain is only 16V
Voltage across R0 is now 0.52 V.
Ac and DC voltages across input to speaker is -
AC - varying 0.4V is the peak that I could see
DC - 0 volts.
Temperature of R0 after 15 minutes is approx - 30 C (the heatsink is a little cooler)
One observation is that if I vary R4 from this point (which is about half a turn from full anti-clockwise) either clockwise or anticlockwise the unregualted voltage input changes in the same direction - it goes up to 32V and keeps rising. The Voltage across R0 drops to 0.42V or less (depending on how much I change R4).
So Temperature looks much better on Q1. However the heatsink temperature after running for nearly half an hour is only around 30C !
I still have the bulb in series with the primary. Should I remove it and see what happens?
thanks
vsr
Hi Till
There was a signal at the input when I measured, I was playing some music through the discman at that point.
I tried with input shorted and the AC voltage across speakers is almost 0 (no variation).
OK, just turned it up without the bulb, so far everything looks ok, no burning smell or excess heating. Measured the temperature of the Q1 drain pin - around 70 and holding (measured over about 10 minutes).
Is this temperature ok? The heatsink temperature is still bothering me, its hardly warm (over 3-4 degress above room temperature) I am using a heatsink used on an Aleph2...but still didnt expect this kind of cooling! Is this reasonable?
Now to the measured values. I adjusted R4 till Q1 drain is about 27V (unregulated voltage was around 52V) The voltage across R0 is only 0.45V. I cannot get this to go any higher unless I bring down the Q1 drain to about 15V.
Now with the above values in place, I played some music and the highs of the music seemed to be distorting, so I reduced Q1 drain down to 19V. At this point R0 is still the same and I seem to be getting non-distorted sound (just based on hearing...no measurements here).
So what can I do to increase the output, right now I seem to be running at lower than the maximum possible output. What is more important to adjust the voltage across the drain of Q1 (such that it is about half of unreg. V + 2 volts) or the voltage across R0 or just base it totally on how it sounds?
i havent measured the R4 value yet, I might do that and post it later (but right now its about 270 degrees turned clockwise all the way from starting point - essentially hasnt completed a turn yet).
I havent ordered the parts for the other blown channel as yet since I was waiting to see if I should order parts for both channels or just one
thanks for all your help Till...hope I can return the favour to some newbie in the near future.
vsr
There was a signal at the input when I measured, I was playing some music through the discman at that point.
I tried with input shorted and the AC voltage across speakers is almost 0 (no variation).
OK, just turned it up without the bulb, so far everything looks ok, no burning smell or excess heating. Measured the temperature of the Q1 drain pin - around 70 and holding (measured over about 10 minutes).
Is this temperature ok? The heatsink temperature is still bothering me, its hardly warm (over 3-4 degress above room temperature) I am using a heatsink used on an Aleph2...but still didnt expect this kind of cooling! Is this reasonable?
Now to the measured values. I adjusted R4 till Q1 drain is about 27V (unregulated voltage was around 52V) The voltage across R0 is only 0.45V. I cannot get this to go any higher unless I bring down the Q1 drain to about 15V.
Now with the above values in place, I played some music and the highs of the music seemed to be distorting, so I reduced Q1 drain down to 19V. At this point R0 is still the same and I seem to be getting non-distorted sound (just based on hearing...no measurements here).
So what can I do to increase the output, right now I seem to be running at lower than the maximum possible output. What is more important to adjust the voltage across the drain of Q1 (such that it is about half of unreg. V + 2 volts) or the voltage across R0 or just base it totally on how it sounds?
i havent measured the R4 value yet, I might do that and post it later (but right now its about 270 degrees turned clockwise all the way from starting point - essentially hasnt completed a turn yet).
I havent ordered the parts for the other blown channel as yet since I was waiting to see if I should order parts for both channels or just one
thanks for all your help Till...hope I can return the favour to some newbie in the near future.
vsr
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