dear uncle charlie
is there any technique that we can use to find the problem in our constructed dx turbo?
I ask this because i know that there are many people who want to assemble this amplifier but they(including me) dont have that much knowledge in troubleshooting.
i read all pages in this thread but it seems that its still hard to find the trouble. what i mean is for example we found that in series protective resistance(10 ohms) we have measured more than 10 volts, so we will suggest him to check for transistor lead interchange, caps polarity, resistor value, loose contact etc etc., in general we are telling him to check everything. Can you teach us how to troubleshoot section by section? For example, to check if the problem is in input stage(section) we will cut(disconnect) a paticular line and check or measure a prticular point, if we measured like this then the problem is that, else, the problem is this. if we can measure something like this then the input stage is working so we will forget it and lets proceed to other section.
I ask this uncle charlie so that me and other people will learn something from experienced and full of knowledge people like you.
Whatever we learn from you i know we can use it or apply it to other amplifier circuit that we may encounter for repair.
i assemble this amplifier but it didnt work. As i power on the circuit and measure the rail voltages the positive rail is 48vdc ( my supply is 50vdc 0 -50vdc ), but my negative rail becomes +5vdc (reference to ground). Im so confuse because from -50vdc it will become +5vdc.
i use the pcb layout of alexmm(the one that tested), i check it with the diagram in gregs site. i cant find any wrong in the layout, all resistor value is correct, the caps are correct and the polarity is in correct posistion. only my small value caps are not following with the schematic because of non availability in the shop, so the 39N i replace with 50N, 220N i replace with 200N etc etc., I think this will not lead to any problem right?
I suspect before that its because of the pin configuration of 2n5401 because from philips the pin 1 is collector but in farechild or motorolla or microelectronics the pin 1 is emitter. But even if i rotate the transistors(interchange left and right pin) still the problem is same, neagtive rail become +5 volts.
i have assembled dxamplifer 2 circuits(if you remember me) and they works but in this (turbo) i didnt succeed. I know there is nothing wrong with the design(because its you who design it), The problem is in my work, but i cant find my mistakes, thats why i ask you to give us stage by stage checking techinique.
Im planning to run this amp in 70 to 80 volts( i have 50 volts ac transformer).
Thanks again uncle carlos for giving us amplifier design that comparable to any leading expensive amp. AND ITS FREE!!
Regards to you and your family
is there any technique that we can use to find the problem in our constructed dx turbo?
I ask this because i know that there are many people who want to assemble this amplifier but they(including me) dont have that much knowledge in troubleshooting.
i read all pages in this thread but it seems that its still hard to find the trouble. what i mean is for example we found that in series protective resistance(10 ohms) we have measured more than 10 volts, so we will suggest him to check for transistor lead interchange, caps polarity, resistor value, loose contact etc etc., in general we are telling him to check everything. Can you teach us how to troubleshoot section by section? For example, to check if the problem is in input stage(section) we will cut(disconnect) a paticular line and check or measure a prticular point, if we measured like this then the problem is that, else, the problem is this. if we can measure something like this then the input stage is working so we will forget it and lets proceed to other section.
I ask this uncle charlie so that me and other people will learn something from experienced and full of knowledge people like you.
Whatever we learn from you i know we can use it or apply it to other amplifier circuit that we may encounter for repair.
i assemble this amplifier but it didnt work. As i power on the circuit and measure the rail voltages the positive rail is 48vdc ( my supply is 50vdc 0 -50vdc ), but my negative rail becomes +5vdc (reference to ground). Im so confuse because from -50vdc it will become +5vdc.
i use the pcb layout of alexmm(the one that tested), i check it with the diagram in gregs site. i cant find any wrong in the layout, all resistor value is correct, the caps are correct and the polarity is in correct posistion. only my small value caps are not following with the schematic because of non availability in the shop, so the 39N i replace with 50N, 220N i replace with 200N etc etc., I think this will not lead to any problem right?
I suspect before that its because of the pin configuration of 2n5401 because from philips the pin 1 is collector but in farechild or motorolla or microelectronics the pin 1 is emitter. But even if i rotate the transistors(interchange left and right pin) still the problem is same, neagtive rail become +5 volts.
i have assembled dxamplifer 2 circuits(if you remember me) and they works but in this (turbo) i didnt succeed. I know there is nothing wrong with the design(because its you who design it), The problem is in my work, but i cant find my mistakes, thats why i ask you to give us stage by stage checking techinique.
Im planning to run this amp in 70 to 80 volts( i have 50 volts ac transformer).
Thanks again uncle carlos for giving us amplifier design that comparable to any leading expensive amp. AND ITS FREE!!
Regards to you and your family
Fix, or repair diy amplifiers is not very easy, because we have many possibilities
Of mistake dear Masterinvi.
First is to check the board, because when we prepare the board, or when we etch at home, them you may have failures, copper lines missed, and during soldering you may have shorts.
So, prepare a schematic copy, a printed schematic and a colour pencil or pen and go watching the board througth strong ligth, put a ligth bulb bellow the board and go inspecting traces and go painting each one of them in your schematic, till you have painted all schematic, trace lines covering or parallel and very near the schematic connection lines... doing this you will find missed lines, shorted lines and interrupted (broken) lines.
Solder once again each solder point, melt the solder and add a little bit of new solder, if you face bubbles in the solder point, there's a bad solder, a problem you may have fixed soldering these points once again.
Then, having all connections removed, as input cable, output cable, positive rail wire, negative rail wire and ground (VBE multiplier too) them measure resistance to search for semiconductors, or transistors shorted, line shorted that you could not discover with visual inspection...measure resistance, high scale, 2 Mega or 20 Mega, you may be patient to wait the meter reading, it will charge electrolitic condensers and will having strange numbers floating, depending the polarity, resistance may reduce to zero and them increase again till will be stable reading several kilo ohms, more than 30K, usually you have more than 500K when everything is all rigth.
Do that from positive to ground, and them invert your multimeter probe tips and measure once again.... register the numbers in a piece of paper, make your notes about the resistances you have found.
Do that now from negative to ground and them invert your multimeter probe tips once again, take notes from the values you have,
Now check from positive to negative and invert your multimeter probe points.
All reading should be high resistances... ohms reading, less than 2K, means shorts.
Having shorts...good!, now clean you board with a brush, cut your brush hairs to make the brush tigth, reduce the brush hair length to make it strong to remove solder flux, use Alcohol, 92 degrees (to medicine use) or use Kerozene, the aviation fuel, remove all flux, clean your board, let it dry or force it dry using hair dryer or sun ligth..measure once again..... short continues?
Then check each transistor, observe first if colector is connected to the colector resistance, check the base is is connected to the base resistance or with other component, and check emitter, do that using light bellow the board, watch the component side, and copper tracks will appear as because board will be transparent to the ligth, and copper tracks will be dark because ligth does not cross metal tracks.. them remove the one you have inspected, write with permanent pen the leads position to put it back once again, write (B) for base, (C) for colector and (E) for emitter...
It is needed to remove, sometimes you find transistor shorted, resistance will be zero, but board use to fool us, so, better will be to remove one by one, you will see that this will save time in the place to spend time as you may think, to be thinking and analising takes too much time, better is to remove them all and meaure them outside, the board has resistances, diodes, other components that may fool you, you may be reading the next transistor and the one under measurement may be open, not conducting. you may think it is fine, but you were measuring other connected to the first one..so, remove them from the board always do that job, seems stupid, you gonna se that it is not, save time!
to be continued....
Of mistake dear Masterinvi.
First is to check the board, because when we prepare the board, or when we etch at home, them you may have failures, copper lines missed, and during soldering you may have shorts.
So, prepare a schematic copy, a printed schematic and a colour pencil or pen and go watching the board througth strong ligth, put a ligth bulb bellow the board and go inspecting traces and go painting each one of them in your schematic, till you have painted all schematic, trace lines covering or parallel and very near the schematic connection lines... doing this you will find missed lines, shorted lines and interrupted (broken) lines.
Solder once again each solder point, melt the solder and add a little bit of new solder, if you face bubbles in the solder point, there's a bad solder, a problem you may have fixed soldering these points once again.
Then, having all connections removed, as input cable, output cable, positive rail wire, negative rail wire and ground (VBE multiplier too) them measure resistance to search for semiconductors, or transistors shorted, line shorted that you could not discover with visual inspection...measure resistance, high scale, 2 Mega or 20 Mega, you may be patient to wait the meter reading, it will charge electrolitic condensers and will having strange numbers floating, depending the polarity, resistance may reduce to zero and them increase again till will be stable reading several kilo ohms, more than 30K, usually you have more than 500K when everything is all rigth.
Do that from positive to ground, and them invert your multimeter probe tips and measure once again.... register the numbers in a piece of paper, make your notes about the resistances you have found.
Do that now from negative to ground and them invert your multimeter probe tips once again, take notes from the values you have,
Now check from positive to negative and invert your multimeter probe points.
All reading should be high resistances... ohms reading, less than 2K, means shorts.
Having shorts...good!, now clean you board with a brush, cut your brush hairs to make the brush tigth, reduce the brush hair length to make it strong to remove solder flux, use Alcohol, 92 degrees (to medicine use) or use Kerozene, the aviation fuel, remove all flux, clean your board, let it dry or force it dry using hair dryer or sun ligth..measure once again..... short continues?
Then check each transistor, observe first if colector is connected to the colector resistance, check the base is is connected to the base resistance or with other component, and check emitter, do that using light bellow the board, watch the component side, and copper tracks will appear as because board will be transparent to the ligth, and copper tracks will be dark because ligth does not cross metal tracks.. them remove the one you have inspected, write with permanent pen the leads position to put it back once again, write (B) for base, (C) for colector and (E) for emitter...
It is needed to remove, sometimes you find transistor shorted, resistance will be zero, but board use to fool us, so, better will be to remove one by one, you will see that this will save time in the place to spend time as you may think, to be thinking and analising takes too much time, better is to remove them all and meaure them outside, the board has resistances, diodes, other components that may fool you, you may be reading the next transistor and the one under measurement may be open, not conducting. you may think it is fine, but you were measuring other connected to the first one..so, remove them from the board always do that job, seems stupid, you gonna se that it is not, save time!
to be continued....
let's continue....
then go removing transistors, one by one, do not remove all them, go one by one, and you will find the shorted one... them replace that one and continue, you may have other, or others.
Doing that you must check if you are using the correct transistor, and you may check in the internet the transistor leads, the base lead, the colector lead and emitter lead, you should download data sheet and watch this carefull, also check three times if you are using a NPN in a place you need a NPN and if you are using a PNP in a place you need PNP....so , transistor will be checked...also you will find fake ones, there are NPN fakes that measure alike PNP.... yes...happened this week with a friend of me!.
Check all transistors.... short remains?... then check if output transistor case is insulated related the heatsink, the output transistor's colectors cannot show resistance to the heatsink, heatsink is usually grounded, a wire must go from a heatsink screw (soldered) to the transformer secondary coil center tap pin, the traditional grounding system.... your colector can be shorted with the heatsink, you have already checked all transistors disconnected (out from the board) so, you know they are fine.
Now electrolitic condensers, remove them and check them, also check if you have installed them in the correct polarity and check the value you have used.
Now check resistances, each one of them, go painting into the schematic each one you lift one side to measure..let one side soldered and measure, this way you will not have the circuit fooling you... take this chance to check values with your multimeter, check value comparing with the schematic value.
Doing that, is almost impossible to remain a failure...but it is hard work, do not engage your brain, it is hard, mechanicall, automatic work, to desolder, to remove parts, to take notes, to measure, and to return to the board, one by one.
This is what i can do to help you..do not waste your time trying to analise why negative rail is having so big power consumption, go measuring and you will find your mistake..measure everything, all capacitors, all condensers, all resistances, all diodes and all transistors..check trimpot, vbe multipler, supply voltages, supply rectifiers and so on.
Be happy, good luck!
regards,
Carlos
then go removing transistors, one by one, do not remove all them, go one by one, and you will find the shorted one... them replace that one and continue, you may have other, or others.
Doing that you must check if you are using the correct transistor, and you may check in the internet the transistor leads, the base lead, the colector lead and emitter lead, you should download data sheet and watch this carefull, also check three times if you are using a NPN in a place you need a NPN and if you are using a PNP in a place you need PNP....so , transistor will be checked...also you will find fake ones, there are NPN fakes that measure alike PNP.... yes...happened this week with a friend of me!.
Check all transistors.... short remains?... then check if output transistor case is insulated related the heatsink, the output transistor's colectors cannot show resistance to the heatsink, heatsink is usually grounded, a wire must go from a heatsink screw (soldered) to the transformer secondary coil center tap pin, the traditional grounding system.... your colector can be shorted with the heatsink, you have already checked all transistors disconnected (out from the board) so, you know they are fine.
Now electrolitic condensers, remove them and check them, also check if you have installed them in the correct polarity and check the value you have used.
Now check resistances, each one of them, go painting into the schematic each one you lift one side to measure..let one side soldered and measure, this way you will not have the circuit fooling you... take this chance to check values with your multimeter, check value comparing with the schematic value.
Doing that, is almost impossible to remain a failure...but it is hard work, do not engage your brain, it is hard, mechanicall, automatic work, to desolder, to remove parts, to take notes, to measure, and to return to the board, one by one.
This is what i can do to help you..do not waste your time trying to analise why negative rail is having so big power consumption, go measuring and you will find your mistake..measure everything, all capacitors, all condensers, all resistances, all diodes and all transistors..check trimpot, vbe multipler, supply voltages, supply rectifiers and so on.
Be happy, good luck!
regards,
Carlos
how are you uncle carlos
i check again the circuit and i found that its my protective resistance as the culprit of droping the voltage in negative rail. it change value from 10 ohms to 150k. i use only 1 watt resistor so that it will easily become hot when some abnormal in the circuit happens.
i power up the circuit without its output transistors because my objective is only to find the cause of dropping the negative rail.
i measure about 400 mv in positive rail and 350mv in negative rail. i measure about 600mv in every transistors(Base to emitter), 2.4v from point A to Point B in bootstrap. But the NPN driver transistor is warm while the PNP is cold(no change in temperature).
No more time in installing the output transistors(time to go home). i will try it tommorrow.
Before if i assemble an amplifier circuit my technique in checking if the circuit is ok is to measure the Collector to Base and Collector to Emitter of the output transistors, they must have a .6 volts defference. Then i will measure if there is dc voltage in output and last i will measure the ac in output while touching the input with my finger. if everything is ok thats the time i connect the speaker.
But now i learned a lot with your techinique(protective resistnce), its more safe for the output transistor. Thank you.
i check again the circuit and i found that its my protective resistance as the culprit of droping the voltage in negative rail. it change value from 10 ohms to 150k. i use only 1 watt resistor so that it will easily become hot when some abnormal in the circuit happens.
i power up the circuit without its output transistors because my objective is only to find the cause of dropping the negative rail.
i measure about 400 mv in positive rail and 350mv in negative rail. i measure about 600mv in every transistors(Base to emitter), 2.4v from point A to Point B in bootstrap. But the NPN driver transistor is warm while the PNP is cold(no change in temperature).
No more time in installing the output transistors(time to go home). i will try it tommorrow.
Before if i assemble an amplifier circuit my technique in checking if the circuit is ok is to measure the Collector to Base and Collector to Emitter of the output transistors, they must have a .6 volts defference. Then i will measure if there is dc voltage in output and last i will measure the ac in output while touching the input with my finger. if everything is ok thats the time i connect the speaker.
But now i learned a lot with your techinique(protective resistnce), its more safe for the output transistor. Thank you.
You are welcome, use your technique and use mine too
Just be happy having both!
regards,
Carlos
Just be happy having both!
regards,
Carlos
uncle carlos i install the output transistors today, my dc offset is adjusted to 1mv, no ac voltage measured at output. my analog multi meter(setted at ac voltage 10 volts) will move as i touch my finger at input. voltage from point A to point B in four diodes is 2.3 volts. I connected the speaker and the audio source but the audio is so low, the output transistors will become hot until you cant touch it, i must off the power for surely they will be damaged very soon.
i have four pairs in output transistors with emmiter resistor of .33 ohms each( thats what i have in my shop). my driver transistors are A1941 and C5198( i think they are not complimentary), the transistors that needs separate heatsink is TIP41.
My input transistors are A992 and C9014( they are not complimentary)
my input transistor(A992) base to emmiter voltage is 500mv , is this ok?
all voltages seems to be normal but audio is low, seems like only 30 watts.
what could be the problem?
Regards and thank you for your patience in answering the people like me who are not that experienced.
i have four pairs in output transistors with emmiter resistor of .33 ohms each( thats what i have in my shop). my driver transistors are A1941 and C5198( i think they are not complimentary), the transistors that needs separate heatsink is TIP41.
My input transistors are A992 and C9014( they are not complimentary)
my input transistor(A992) base to emmiter voltage is 500mv , is this ok?
all voltages seems to be normal but audio is low, seems like only 30 watts.
what could be the problem?
Regards and thank you for your patience in answering the people like me who are not that experienced.
12V across the Zener changes the currents that flow.
You need to recalculate the resistors to get the currents back to design values.
You need to recalculate the resistors to get the currents back to design values.
Better to keep the original value, i am using different values, but this changes the
long tail resistance values to allow you to have small of set, and also you will have different current to the zener.
Do not change this stuff, because will create troubles.
regards,
Carlos
long tail resistance values to allow you to have small of set, and also you will have different current to the zener.
Do not change this stuff, because will create troubles.
regards,
Carlos
Unstability found during the clipping, square wave full power
this may turn the clipping sonics worse, a dirty tones may appear, so, better to install (If you find the same in your scope) 470pf from the VBE multiplier emitter to ground.
This capacitor must be high voltage, at least rail to rail voltage, as will face VAS swing.
regards,
Carlos
this may turn the clipping sonics worse, a dirty tones may appear, so, better to install (If you find the same in your scope) 470pf from the VBE multiplier emitter to ground.
This capacitor must be high voltage, at least rail to rail voltage, as will face VAS swing.
regards,
Carlos
I do not know Masterinvi, you should search for errors, because for sure they exist
Have you connected the gain resistance in series with an electrolitic condenser (R9 and C7).
Something is wrong and only you can discover observing your own construction, i cannot do that for you.
I do not even imagine what is going on at your place.
regards,
Carlos
Have you connected the gain resistance in series with an electrolitic condenser (R9 and C7).
Something is wrong and only you can discover observing your own construction, i cannot do that for you.
I do not even imagine what is going on at your place.
regards,
Carlos
I was thinking about you Masterinvi
2.3 volts measured using analog multimeter can have enormous errors, you can have, for instance 2.5 volts, and this means more than 8 watts of power wasted in each one of your power resistances, excess of current is possible there, and having many transistors you will have something alike an enormous soldering iron overheating your heatsinks, off course they will not survive for too long.
First you have to find a digital multimeter and abandon your analogic one to produce these adjustments, with a digital multimeter, 200 milivolts DC scale, check voltage directly over each one of your emitter resistance, and adjust in a such way you will have less than 1 milivolts into each one of them, yes, they can be sligthly different, as each transistor can have different gain.
just be sure your multimeter is reading something, not overflow, you need just to be sure each transistor is conducting, and when they conduct you will have milivolts developed above the power emitter resistances (power equalizing resistances).
500 milivolts using analogic multimeter says nothing for us, this can be 520 milivolts, and this is good, but can be 480 milivolts and this is bad... you should, immediatelly, buy or borrow a digital multimeter or measure these DC points using a calibrated Oscilloscope.
These first transistors, normal voltage i have measured today is 575 milivolts each one of them.
I think you have removed the protective resistances, they are there only to adjustments, you must remove them to use your amplifier, they must be substituted by fuses, also use a fuse in the output line too.
Speaker must be strong, if you have one fuse burned, then you gonna have rail voltage at your output, rail voltage over a speaker may burn it...sometimes fuses fails, so, the speaker must be strong to face high power for some seconds (50 seconds) to give the operator time to flip the power switch off.
If you have an electronic protection, relay protection, then use it, this range of power is very dangerous, as you are using high voltage supply, this means troubles if something wrong happens with your amplifier.
Give a kiss in your beloved analogic multimeter, but please, keep it out of this adjustment, they are not something we can trust, have no precision in the reading.
Correctly adjusted, the stand by current, the bias trimpot, them your power transistors, without signal will face less than 100 miliwatts each one of them, this means amplifier dead cold...
Remove speaker and measure resistance from the power amplifier output to the ground, you may have some ohms there and this is not correct, this would be another explanation about the low power or the overheating, as another load in parallel will suck enormous energy from the power amplifier.
Your Zobel filter resistance is 4.7 ohms, but if correctly assembled it is in series with a capacitor...well, if this capacitor is shorted because have faced excess of voltage swing, then you will have 4.7 ohms load to ground.... check this.
regards,
Carlos
2.3 volts measured using analog multimeter can have enormous errors, you can have, for instance 2.5 volts, and this means more than 8 watts of power wasted in each one of your power resistances, excess of current is possible there, and having many transistors you will have something alike an enormous soldering iron overheating your heatsinks, off course they will not survive for too long.
First you have to find a digital multimeter and abandon your analogic one to produce these adjustments, with a digital multimeter, 200 milivolts DC scale, check voltage directly over each one of your emitter resistance, and adjust in a such way you will have less than 1 milivolts into each one of them, yes, they can be sligthly different, as each transistor can have different gain.
just be sure your multimeter is reading something, not overflow, you need just to be sure each transistor is conducting, and when they conduct you will have milivolts developed above the power emitter resistances (power equalizing resistances).
500 milivolts using analogic multimeter says nothing for us, this can be 520 milivolts, and this is good, but can be 480 milivolts and this is bad... you should, immediatelly, buy or borrow a digital multimeter or measure these DC points using a calibrated Oscilloscope.
These first transistors, normal voltage i have measured today is 575 milivolts each one of them.
I think you have removed the protective resistances, they are there only to adjustments, you must remove them to use your amplifier, they must be substituted by fuses, also use a fuse in the output line too.
Speaker must be strong, if you have one fuse burned, then you gonna have rail voltage at your output, rail voltage over a speaker may burn it...sometimes fuses fails, so, the speaker must be strong to face high power for some seconds (50 seconds) to give the operator time to flip the power switch off.
If you have an electronic protection, relay protection, then use it, this range of power is very dangerous, as you are using high voltage supply, this means troubles if something wrong happens with your amplifier.
Give a kiss in your beloved analogic multimeter, but please, keep it out of this adjustment, they are not something we can trust, have no precision in the reading.
Correctly adjusted, the stand by current, the bias trimpot, them your power transistors, without signal will face less than 100 miliwatts each one of them, this means amplifier dead cold...
Remove speaker and measure resistance from the power amplifier output to the ground, you may have some ohms there and this is not correct, this would be another explanation about the low power or the overheating, as another load in parallel will suck enormous energy from the power amplifier.
Your Zobel filter resistance is 4.7 ohms, but if correctly assembled it is in series with a capacitor...well, if this capacitor is shorted because have faced excess of voltage swing, then you will have 4.7 ohms load to ground.... check this.
regards,
Carlos
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actually i have didgital multimeter uncle carlos, i buy this meter while i was working in other country(Dubai of (Arab Emirates)), My Analog reads exactly same with my digital in measuring volts ac-dc and resistance.
Anyway, You are correct in suspecting the caps in zobel it is shorted ,i didnt suspect it because its new , yes it is the cause of Overheating the outputs.
Using my digital i measure all point you mention in your Voltage reference File, everything is ok except Point A to Point B which reads 2 volts to 2.3 volts (adjusting the bias trimpot from lowest to highst ohms).
Also Base voltage of input transistor(reference to ground) which its supposed to be 120 mv is only 10mv to 45 mv (depend on my adjustment of dc offset). I wonder why it wont reach 120 mv( checked already the 33k and its paralled caps and they are okey). maybe its the cause why my Audio output is still low, Any suggestion?
I measure the base of Feedback transistor(ref to ground) i got 120 mv, is it okey?
i got 50 mv in 82 ohms resistor of negative rail to npn transistor as indicated in your Reference file.
Output Transistor will become Hot if I fully adjust the Bias trimpot (2.3 volts will be read in Point A to Point B)
I only use 1 pair of Outputs at this time, if they will not turn Hot and if there Audio output will become normal then thats the time i will connect the other pair.
I will try and try and check and check until i will discover my mistake
Regards
Anyway, You are correct in suspecting the caps in zobel it is shorted ,i didnt suspect it because its new , yes it is the cause of Overheating the outputs.
Using my digital i measure all point you mention in your Voltage reference File, everything is ok except Point A to Point B which reads 2 volts to 2.3 volts (adjusting the bias trimpot from lowest to highst ohms).
Also Base voltage of input transistor(reference to ground) which its supposed to be 120 mv is only 10mv to 45 mv (depend on my adjustment of dc offset). I wonder why it wont reach 120 mv( checked already the 33k and its paralled caps and they are okey). maybe its the cause why my Audio output is still low, Any suggestion?
I measure the base of Feedback transistor(ref to ground) i got 120 mv, is it okey?
i got 50 mv in 82 ohms resistor of negative rail to npn transistor as indicated in your Reference file.
Output Transistor will become Hot if I fully adjust the Bias trimpot (2.3 volts will be read in Point A to Point B)
I only use 1 pair of Outputs at this time, if they will not turn Hot and if there Audio output will become normal then thats the time i will connect the other pair.
I will try and try and check and check until i will discover my mistake
Regards
I see you cannot reduce the bias 2.3V with your trimpot in the minimum resistance
position, them try to install 100 ohms resistance in parallel with one of your diodes, only one of them, if not good enougth to reduce a little this 2.3 to 2.15, them decrease this resistance to 47 ohms, or install another in parallel with the previous one.
Reduce the gain resistance, as you want more gain, try 470 ohms or even lower resistance, then you sensitivity problem will be solved.
The amplifier needs 750 mV rms to achieve full power output in 8 ohms loads, when using 4 ohms you may need a little bit more drive i imagine.... i hope your signal source is not a damn Ipod or i will make a cerimonial harakiri so shocked i will be!... very ashamed i will be, hardly schocked near to be scandalized!...if you produce pictures (please do it!) them remove that "thing" from the image please, i am fat, old and i have no strong heart to see that.
ahahahahah!
Carlos
position, them try to install 100 ohms resistance in parallel with one of your diodes, only one of them, if not good enougth to reduce a little this 2.3 to 2.15, them decrease this resistance to 47 ohms, or install another in parallel with the previous one.
Reduce the gain resistance, as you want more gain, try 470 ohms or even lower resistance, then you sensitivity problem will be solved.
The amplifier needs 750 mV rms to achieve full power output in 8 ohms loads, when using 4 ohms you may need a little bit more drive i imagine.... i hope your signal source is not a damn Ipod or i will make a cerimonial harakiri so shocked i will be!... very ashamed i will be, hardly schocked near to be scandalized!...if you produce pictures (please do it!) them remove that "thing" from the image please, i am fat, old and i have no strong heart to see that.
ahahahahah!
Carlos
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i can reduce but only to 2 volts, if i will increase it will be only up to 2.3 volts can not reach 3 volts
30 mv in input transistor base with reference to ground is okey? or must be 120 mv
No im not using ipod, i know they are not good.
Im using DVD player , the one i use in building your dx amp (not turbo)
30 mv in input transistor base with reference to ground is okey? or must be 120 mv
No im not using ipod, i know they are not good.
Im using DVD player , the one i use in building your dx amp (not turbo)
Last edited:
It is fine, do not worry about that, better to be this way, seems you may
have bigger VBE too.
Check milivolts over power transistor emitter resistance, reduce to 1 milivolt or less, check i you have too much heat this way.
regards,
Carlos
have bigger VBE too.
Check milivolts over power transistor emitter resistance, reduce to 1 milivolt or less, check i you have too much heat this way.
regards,
Carlos
over heat in output transistors already solved, that was because of shorted caps in zobel.
the remaining problem is the low audio output
Output will become Hot even no music input if i increase the Point A to Point B voltage to 2.2 or 2.3 volts (bias trimpot almost full) But if lower , the output trans become very cold.
the remaining problem is the low audio output
Output will become Hot even no music input if i increase the Point A to Point B voltage to 2.2 or 2.3 volts (bias trimpot almost full) But if lower , the output trans become very cold.
Strange my dear, you may have errors remaining.
This happens, many time a day here in my home.
Today i have made not too much mistakes, because i did nothing today, just watching television and cooking pizza.
You will find, keep going, you will find.
regards,
Carlos
This happens, many time a day here in my home.
Today i have made not too much mistakes, because i did nothing today, just watching television and cooking pizza.
You will find, keep going, you will find.
regards,
Carlos
1 more question, my digital and analog meter can not detect an open low value capacitor, What will happen if the small caps that paralleled with the electro caps that in series with gain resistance is open? does it will result to this problem?
i have ESR meter that i use in repairing television set , i checked all electtrocaps and all of them are good, only the small values i cant checked thats why i ask you what if this small caps is open?
i have ESR meter that i use in repairing television set , i checked all electtrocaps and all of them are good, only the small values i cant checked thats why i ask you what if this small caps is open?
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