Re: Attention Dx constructors, a very important message.
You explained everything related multiturn very well....
Although i can also agree with you Carlos related this topic - in my building practice i would never use "normal" circular, one turn trimpots....few reasons - one is that multiturn has better protected internal conductive layer (against environment) than one turn trimpots.... other reason is that it is more precise ... and also because of the better protection against environment it is more secure that it will have contact between conductive layer and contacts......
but as you pointed out Carlos single turn is more easy to use than multiturn.....this problem related missadjustements can be solved with fast switching of if we measure to high bias current.... that is how i do it... if the current is to high - much higher than expected and that i fear about the safety of the amp - i turn the amp off and adjust the bias while it is cooling down....than i turn it on and meassure again....and i am allways starting with turning on just one channel and from the lowest bias current ... after succesfull turn on with the current lower than needed i slowly turn the multiturn to the desired current... problem solved....
there is also here a discussion related the materials in multiturn and single turn trimpot.... conductive material is different...
destroyer X said:
You explained everything related multiturn very well....
Although i can also agree with you Carlos related this topic - in my building practice i would never use "normal" circular, one turn trimpots....few reasons - one is that multiturn has better protected internal conductive layer (against environment) than one turn trimpots.... other reason is that it is more precise ... and also because of the better protection against environment it is more secure that it will have contact between conductive layer and contacts......
but as you pointed out Carlos single turn is more easy to use than multiturn.....this problem related missadjustements can be solved with fast switching of if we measure to high bias current.... that is how i do it... if the current is to high - much higher than expected and that i fear about the safety of the amp - i turn the amp off and adjust the bias while it is cooling down....than i turn it on and meassure again....and i am allways starting with turning on just one channel and from the lowest bias current ... after succesfull turn on with the current lower than needed i slowly turn the multiturn to the desired current... problem solved....
there is also here a discussion related the materials in multiturn and single turn trimpot.... conductive material is different...
Oooh I did sleep well... its almost 10 o' clock and I only woke up now...
as said before it ws not the transistors being faulty it was just the bias pot being set incorrectly...
Working well now, it was just way overbiased.... everything stays cool now, not a single transistor damaged.
The transistor is not fake, a fake is an immitation... I.e. it would try to look like a Toshiba.. but this one does not....
You get bd139 from ST micro, phillips etc... it is not fakes... just other manufacturers....
A fake pretends to be what it is not.
The bias servo has 270R as protection before the trimpot.
I will measure correct settings to help our friends avoid the trouble... the trimpot is a good quality one, made by Bournes.
My method is to switch on amp only long enough to get a reading on the multimeter... then if it is far out. I first switch it off do a bit of adjusting, power on for 5 seconds to see if pot was turned the right way...
If it is close enough to the value I want I start adjusting it with the amp switched on. I hated trying to adjust bias with single turn pots... can never do fine adjustment.
I must just get a new resistor to replace the one I damaged in the PSU, then I can put everything together again...
Overall I am very happy... new board does not have the slight humm from the prototype... I suspect due to the corrected grounding on the one capacitance multiplier. I connected a speaker to it, and it was dead quiet... so quiet I had to put multimeter on output just to make sure it was on. Yihaaaaaa I did something right for a change...
as said before it ws not the transistors being faulty it was just the bias pot being set incorrectly...
Working well now, it was just way overbiased.... everything stays cool now, not a single transistor damaged.
The transistor is not fake, a fake is an immitation... I.e. it would try to look like a Toshiba.. but this one does not....
You get bd139 from ST micro, phillips etc... it is not fakes... just other manufacturers....
A fake pretends to be what it is not.
The bias servo has 270R as protection before the trimpot.
I will measure correct settings to help our friends avoid the trouble... the trimpot is a good quality one, made by Bournes.
My method is to switch on amp only long enough to get a reading on the multimeter... then if it is far out. I first switch it off do a bit of adjusting, power on for 5 seconds to see if pot was turned the right way...
If it is close enough to the value I want I start adjusting it with the amp switched on. I hated trying to adjust bias with single turn pots... can never do fine adjustment.
I must just get a new resistor to replace the one I damaged in the PSU, then I can put everything together again...
Overall I am very happy... new board does not have the slight humm from the prototype... I suspect due to the corrected grounding on the one capacitance multiplier. I connected a speaker to it, and it was dead quiet... so quiet I had to put multimeter on output just to make sure it was on. Yihaaaaaa I did something right for a change...
Carlos, your language skills are fine - no problem understanding you at all, though your diagrams are still helpful.
Nordic's schematic has a 270 ohm resistor in series with the 1k trimpot.
Using the values you supplied as a guide, I would think the values on Nordics schematic would not need to be changed, and would be quite safe if the trimpot was set to a low value to begin with. This would not need to be lower than 300 ohms giving 270 + 300 = 570ohms as a starting value.
Sparkle's suggestions of adjusting one channel at a time and switching off the amp at the first sign of a problem should save any dramas.
I very much appreciate your desire to help. Your enthusiastic involvement, for me, is what make the Dx amp so very interesting and involving, and a great learning experience.
Regards, billabong.
Nordic's schematic has a 270 ohm resistor in series with the 1k trimpot.
Using the values you supplied as a guide, I would think the values on Nordics schematic would not need to be changed, and would be quite safe if the trimpot was set to a low value to begin with. This would not need to be lower than 300 ohms giving 270 + 300 = 570ohms as a starting value.
Sparkle's suggestions of adjusting one channel at a time and switching off the amp at the first sign of a problem should save any dramas.
I very much appreciate your desire to help. Your enthusiastic involvement, for me, is what make the Dx amp so very interesting and involving, and a great learning experience.
Regards, billabong.
Well boys, in the reality you are skilled... already have done constructions
I have received 4 mails...there are 4 guys that never have used a soldering iron before.... first try will be over High Resolution boards....
Oh my God...mein Got!.
One of those folks are reading how to solder.
Nordic has miles and miles over this soldering road...experienced with computers...also made many boards, not only Dx...he is not a beginner... also Billabong is not a beginner... ES44 knows a lot, just read his postings!.... Sparkle is a grandfather related the use of soldering iron...he can solder with the two hands...well.... well..i am not worried about him, he do not use to construct my amplifiers because he knows how to make even better ones!
It seems very obvious to us to check fast, switching the power supply on and off.... we do not enter panic.... we have the self confidence experienced folks have.... we do not feel desperated.
One folk wrote to me in panic because found 900 miliamps.... had trimpot on preset values... starting value...better to be 700 total value..fixed plus the variable one, added, as a starting point... and this variates( the correct adjustment is variable...will be different from circuit to circuit) as you know, reason why everyone uses trimpot there.
Other wrote me telling me the VBE multiplier is not working...the trimpot not adjusting.... transistor inverted or trimpot soldered wrong or hard oscilations...you see... those things happens.
We have also a girl constructing too...and another kind South American friend had troubles also... and i could perceive was mistakes from them, as they have not returned another mail..so...have fixed and felt ashamed to tell me..hehehe..this is normal, happens usually too.
Those folks can enter panic...human reaction to switch off things delays near 1 second.... during panic delays more..... some output can go if the rail selection resistance, the protective one, was selected to a very low value, 5 ohms for instance...or 3.3 ohms..or something they have at hand...i remember we had a friend that used 0.1 or 0.22 or 0.33 ohms in series.... you see that is possible to burn things....with a 3.3 ohms resistance your current will jump easy to 10 amps...or can jump to 10 amps with errors into the soldering, as shorts for instance....inverted transistors also....BD139 and BD140 are "invertable"...possible to be reverted into the board...say.... the pins enter into the holes, even having board indications the one can do that...not impossible.
I do not think you are a good representation, statistics, of the constructor's universe.... you have miles of experience....but i will relax, as i have already mentioned those cares, that were discussed into earlier posts.
Boys!.... there are folks very green....really green into the subject..one near friend, a king guy, is a botanic..this one is "green" by profession, as he use to take care of plants, study plants, develop plants and search for medicinal drugs from plants.... this one have assembled Tripath... this makes him not so bad...he also have a DAC..if made by him everything will be all rigth.
Nordic is supplying pre adjusted trimpots, this will be very helpfull, but there are other folks that are finishing construction into their home made boards, there are two that have already finished... both South Americans, that do not enters, normally, group buys because in dollares boards are extremelly expensive for us..also because we do not trust our own mail system... those ones can produce errors, having the starting point dear Billabong said.... 270 ohms with a 1K trimpot in series...of course adjusted to produce something alike 570 ohms or around that... well... the guy can misadjust... see the attached image the result.... i have to think into those ones too.
Yeah...maybe i worried too much...but read the thread and you will see how many problems we had..so.... carefull about my friends, to take care of them is not a bad idea.
regards,
Carlos
I have received 4 mails...there are 4 guys that never have used a soldering iron before.... first try will be over High Resolution boards....
Oh my God...mein Got!.
One of those folks are reading how to solder.
Nordic has miles and miles over this soldering road...experienced with computers...also made many boards, not only Dx...he is not a beginner... also Billabong is not a beginner... ES44 knows a lot, just read his postings!.... Sparkle is a grandfather related the use of soldering iron...he can solder with the two hands...well.... well..i am not worried about him, he do not use to construct my amplifiers because he knows how to make even better ones!
It seems very obvious to us to check fast, switching the power supply on and off.... we do not enter panic.... we have the self confidence experienced folks have.... we do not feel desperated.
One folk wrote to me in panic because found 900 miliamps.... had trimpot on preset values... starting value...better to be 700 total value..fixed plus the variable one, added, as a starting point... and this variates( the correct adjustment is variable...will be different from circuit to circuit) as you know, reason why everyone uses trimpot there.
Other wrote me telling me the VBE multiplier is not working...the trimpot not adjusting.... transistor inverted or trimpot soldered wrong or hard oscilations...you see... those things happens.
We have also a girl constructing too...and another kind South American friend had troubles also... and i could perceive was mistakes from them, as they have not returned another mail..so...have fixed and felt ashamed to tell me..hehehe..this is normal, happens usually too.
Those folks can enter panic...human reaction to switch off things delays near 1 second.... during panic delays more..... some output can go if the rail selection resistance, the protective one, was selected to a very low value, 5 ohms for instance...or 3.3 ohms..or something they have at hand...i remember we had a friend that used 0.1 or 0.22 or 0.33 ohms in series.... you see that is possible to burn things....with a 3.3 ohms resistance your current will jump easy to 10 amps...or can jump to 10 amps with errors into the soldering, as shorts for instance....inverted transistors also....BD139 and BD140 are "invertable"...possible to be reverted into the board...say.... the pins enter into the holes, even having board indications the one can do that...not impossible.
I do not think you are a good representation, statistics, of the constructor's universe.... you have miles of experience....but i will relax, as i have already mentioned those cares, that were discussed into earlier posts.
Boys!.... there are folks very green....really green into the subject..one near friend, a king guy, is a botanic..this one is "green" by profession, as he use to take care of plants, study plants, develop plants and search for medicinal drugs from plants.... this one have assembled Tripath... this makes him not so bad...he also have a DAC..if made by him everything will be all rigth.
Nordic is supplying pre adjusted trimpots, this will be very helpfull, but there are other folks that are finishing construction into their home made boards, there are two that have already finished... both South Americans, that do not enters, normally, group buys because in dollares boards are extremelly expensive for us..also because we do not trust our own mail system... those ones can produce errors, having the starting point dear Billabong said.... 270 ohms with a 1K trimpot in series...of course adjusted to produce something alike 570 ohms or around that... well... the guy can misadjust... see the attached image the result.... i have to think into those ones too.
Yeah...maybe i worried too much...but read the thread and you will see how many problems we had..so.... carefull about my friends, to take care of them is not a bad idea.
regards,
Carlos
Attachments
I agree with you Carlos, and the truth is these boards are not easy to solder due to small pad sizes, a small tip for soldering iron is advised for most pads... next version, I will make larger pads... also if you have adjutsable soldering iron, note that the silver immersion layer needs a little more heat than tinned boards... I found a good temperature at about 350C 650F.
Do not touch any soldering pads with your fingers as the oils will make a shield against soldering... good idea to wipe clean boards with alcohol or acetone first (yes it is acetone safe, I tested).
If a pad looks a little small, feel free to scrath of some of the blue mask around it, to expose more copper... I only had to do this on one board, and one pad, mainly because I touched it with dirty hands.
____________________________
On the topic of makeing mistakes, this is how I learned and how you got your name. I learned by burning transistors, they are cheap enough.
When you started DX thread in February, what did I know about SS? NOTHING basicaly!!!!! But I built it, and asked questions when things seemed unclear, sometimes I got answers, sometimes there was nothing more to be done than to recheck everything on my own, learn how to identify dead transistors (btw all transistors shipped haved been tested).
You can; A) buy a ready made amp in the shop, B)go study eletronics and then still don't have the practical experience for a long time, or C) simply build it, and learn from your mistakes...or learn from other's mistakes
--------------------------------------
I think we will be able to walk everyone through building successfull amps.
You taught me, and now it is my turn to help carry the fire.
________________________
PS I have on the first HRII connected the bias servo's wires the wrong way around... no damage caused... just didn't work.
Almost all the bad errors killed the bd139 in Q9... and did no damage further.
Do not touch any soldering pads with your fingers as the oils will make a shield against soldering... good idea to wipe clean boards with alcohol or acetone first (yes it is acetone safe, I tested).
If a pad looks a little small, feel free to scrath of some of the blue mask around it, to expose more copper... I only had to do this on one board, and one pad, mainly because I touched it with dirty hands.
____________________________
On the topic of makeing mistakes, this is how I learned and how you got your name. I learned by burning transistors, they are cheap enough.
When you started DX thread in February, what did I know about SS? NOTHING basicaly!!!!! But I built it, and asked questions when things seemed unclear, sometimes I got answers, sometimes there was nothing more to be done than to recheck everything on my own, learn how to identify dead transistors (btw all transistors shipped haved been tested).
You can; A) buy a ready made amp in the shop, B)go study eletronics and then still don't have the practical experience for a long time, or C) simply build it, and learn from your mistakes...or learn from other's mistakes
--------------------------------------
I think we will be able to walk everyone through building successfull amps.
You taught me, and now it is my turn to help carry the fire.
________________________
PS I have on the first HRII connected the bias servo's wires the wrong way around... no damage caused... just didn't work.
Almost all the bad errors killed the bd139 in Q9... and did no damage further.
Mails goes arriving here Nordic... and i realise i cannot stay over the guys shoulder
It is impossible to check the circuit for them because of the distance... this needs our presence.... to do the job in the place of them.... to debug for them.
Yes.... i have concerns, they do not reach your pre adjusted boards...but the other ones that decided, with a lot of courage, to make by themselves.
Those guys deserves my respect..and concerns too.
regards,
Carlos
It is impossible to check the circuit for them because of the distance... this needs our presence.... to do the job in the place of them.... to debug for them.
Yes.... i have concerns, they do not reach your pre adjusted boards...but the other ones that decided, with a lot of courage, to make by themselves.
Those guys deserves my respect..and concerns too.
regards,
Carlos
Attachments
Never fear.... i am here!
I will have my worries and concerns but i will be here to help everyone.
panzertoo@yahoo.com
regards,
Carlos
I will have my worries and concerns but i will be here to help everyone.
panzertoo@yahoo.com
regards,
Carlos
Attachments
Ahahahha... a friend mailed me a message saying
- "If you need a fast adjustment into your bias trimpot is because you are in a deep ship!".... ahahahahha!... have to say that i like this guy...he use to go direct to the point.
Ship, you know...sea sick..that disease..other words cannot be used....only when you crash your toe against the wall frame..or your wife's mother come to stay for long time with you inside your home.
Yes...he is rigth....but for mistaken sittuations, as happens with misadjustments, the fast reaction will be interesting.
Attached a new updated, corrected, more safe, that will work too, and better to beginners than the former schematic...this will be fixed into Greg Home page.... Nordic boards will go with pre adjusted trimpots, and this will be plug and play..will be safe...this new schematic, upgraded, updated, adjusted, sligtly modified is suggested to the ones will produce their own boards...Yes!...they can use multiturns with this new schematic...nothing will burn!
Remember folks that Destroyer X name was created because i used to burn transistors when learning... i was a transistor and circuits destroyer...and more than that... "X" is from Extra... and extra super hiper capability to destroy things....so... i know what is to make mistakes...i am PHD into make errors into circuits!
hehe.... a deep ship was terrible!
regards,
Carlos
- "If you need a fast adjustment into your bias trimpot is because you are in a deep ship!".... ahahahahha!... have to say that i like this guy...he use to go direct to the point.
Ship, you know...sea sick..that disease..other words cannot be used....only when you crash your toe against the wall frame..or your wife's mother come to stay for long time with you inside your home.
Yes...he is rigth....but for mistaken sittuations, as happens with misadjustments, the fast reaction will be interesting.
Attached a new updated, corrected, more safe, that will work too, and better to beginners than the former schematic...this will be fixed into Greg Home page.... Nordic boards will go with pre adjusted trimpots, and this will be plug and play..will be safe...this new schematic, upgraded, updated, adjusted, sligtly modified is suggested to the ones will produce their own boards...Yes!...they can use multiturns with this new schematic...nothing will burn!
Remember folks that Destroyer X name was created because i used to burn transistors when learning... i was a transistor and circuits destroyer...and more than that... "X" is from Extra... and extra super hiper capability to destroy things....so... i know what is to make mistakes...i am PHD into make errors into circuits!
hehe.... a deep ship was terrible!
regards,
Carlos
Attachments
Carlos, your updated Bias Servo sure makes bias adjustment trouble free.
It is just that since Nordic has supplied the pre-adjusted 1k trimpot, it is an added inconvenience to have to source alternate parts for the better circuit, though I may still do that.
I made a mistake when I said the 1k trimpot could be preset to 300 ohms- I should have said 400 ohms, giving a total 670ohms (400+270). Just proves the point you made that your modification protects against mistakes.
Regards,
billabong.
It is just that since Nordic has supplied the pre-adjusted 1k trimpot, it is an added inconvenience to have to source alternate parts for the better circuit, though I may still do that.
I made a mistake when I said the 1k trimpot could be preset to 300 ohms- I should have said 400 ohms, giving a total 670ohms (400+270). Just proves the point you made that your modification protects against mistakes.
Regards,
billabong.
Aussies are lovely...all them clever...cooperative and humble
Thank you Billabong...you got my idea... the intention.
If some problem happens in my country... revolution... social problems...new dictatorial government or too much corruption (more than we already have...reaching my top limits of saturation about that)... Australia will be my final destination.
regards,
Carlos
Thank you Billabong...you got my idea... the intention.
If some problem happens in my country... revolution... social problems...new dictatorial government or too much corruption (more than we already have...reaching my top limits of saturation about that)... Australia will be my final destination.
regards,
Carlos
For those guys who are useing my parts....
i.e. 2k2, 270R, and 1k trimpot:
After connecting bias servo to amp boards, use ohmmeter, negative probe goes to point on board marked servo- and positive goes to servo+, adjust the trimpot on the servo until the meter reads 3000 ohms (3k). You might want to adjust bias after power on to match channels, andaccommodate smaller heatsinks.
This method will also check that your bias servo is put together correctly. I will upload the new servo to the website a.s.a.p. (the one as per the kit parts)the one on the site is the original servo, but it can also be used with peace of mind. I don't use the small elco.
i.e. 2k2, 270R, and 1k trimpot:
After connecting bias servo to amp boards, use ohmmeter, negative probe goes to point on board marked servo- and positive goes to servo+, adjust the trimpot on the servo until the meter reads 3000 ohms (3k). You might want to adjust bias after power on to match channels, andaccommodate smaller heatsinks.
This method will also check that your bias servo is put together correctly. I will upload the new servo to the website a.s.a.p. (the one as per the kit parts)the one on the site is the original servo, but it can also be used with peace of mind. I don't use the small elco.
Hola Carlos, quiero agradecerte por tu preocupación y pedirte disculpas por molestarte. A veces la gente de mi ciudad no brinda ayuda a los principiantes como yo, por eso recurro a ustedes. Me gusta mucho la electrónica (amplificadores de audio) pero no soy experto, solo hobby. Pido ayuda a ustedes ya que anoche tuve mi ultimo percance y hoy estoy muy triste. Saludos y muchas gracias por compartir información conmigo. La resistencia de 180r explotó y bc546 se quemo. 2SA1943 muy caliente. Estoy muy ansioso por disfrutar de este amplificador ya que hace 1 mes que vengo escuchando DxStandar en mi auto y estoy muy conforme.
Hola Carlos, I want(love) to be grateful for you for your worry and ask you for excuses for bothering. Sometimes the people of my city do not drink help to the beginners since(as,like) me, because of it I resort to you. I like much the electronics (audio amplifier) but I am not an expert, alone hobby. I ask you for help since last night I had my last mishap and today I am very sad. Regards and thank you very much for sharing information with me. The resistance of 180r exploited and bc546 I am hot. 2SA1943 very warm. I am very eager to enjoy this amplifier since it(he,she) does 1 next month listening TO DxStandar in my car and I am very similar.
Sorry, bad english.
Hola Carlos, I want(love) to be grateful for you for your worry and ask you for excuses for bothering. Sometimes the people of my city do not drink help to the beginners since(as,like) me, because of it I resort to you. I like much the electronics (audio amplifier) but I am not an expert, alone hobby. I ask you for help since last night I had my last mishap and today I am very sad. Regards and thank you very much for sharing information with me. The resistance of 180r exploited and bc546 I am hot. 2SA1943 very warm. I am very eager to enjoy this amplifier since it(he,she) does 1 next month listening TO DxStandar in my car and I am very similar.
Sorry, bad english.
Attachments
Hay errores en el circuito...there are errors into your construction
As you have parts blowing, for sure hard unballance of voltages and current are running into your amplifier.
I hope you are using the protective resistances in series with the rails...they are needed...to avoid burns.
You have to check all your transistors positions...if not assembled into wrong position, need to know the base lead, colector and emitter and need to measure each one of them to check if someone more is damaged.... inform if you know how to measure transistors and if you have the correct identification to all of them... say...base, colector and emitter leads.
You will need to check resistances, if values are the same into the schematic and the whole circuit for shorts...measuring resistances into the board with power off, searching for low resistances.
Resistance measurements from plus to minus... from plus to ground, and from minus to ground...and inverting you probe points will show problems too...and the rail you have something wrong.
Also, of course, you need to check your supply polarity..if the positive wire you are using is really positive...and so on...also to check if voltages are the same into positive rail and negative rail..same value with opposite polarities, of course.
I cannot do too much from Recife to your place...just to listen your problems and try to teach you methods to track defects..some of them already written.
VBE is a good idea of the stage sittuation.... measuring voltages from base to emitter will tell you if the unit is working fine in that stage you are measuring... the input circuit, base to emitter will be checked this way...voltages goes from 400 to 800 there...good when goes from 580 to 640 milivolts (my experience).
I can give you a voltage chart....but you will be on troubles to debug watching voltage charts...if not experienced will feel yourself lost... the better idea is to remove each transistor and measure out from the circuit, or to lift, at least 2 leads to measure.
The measurement is the diode position you have into your multimeters...start with the black lead into the base and them touch the red lead into the colector and after that into the emitter.
Now invert.... fix the red lead into the base... and them touch the black lead into the colector and after that into the emitter.
A good transistor will conduct in one polarity and will not conduct in the other...you will measure something near 600 into your digital multimeter into the diode position... the value can be different...the logics of polarities have to be obbeyed..if not...problems.
The damaged transistor normally present short circuit between leads.... you have no shorts, not low resistance into a transistor...so...the presence of short, not matter the lead is... shows the unit as damaged.
A good idea is to check from colector to emitter and repeating the same measurement with inverted polarities.
Use the bias adjustment i suggested.... 680 ohms fixed resistance in series with a 100 ohms trimpot.... watch the images in the previous posts...i have checked this now...real life... i have made the amplifier once again, with the schematic values and adjusted perfectly and easy.
Burns means errors...and now all transistors need to be checked...also electrolitic condenser polarities will need check.
The BD139 and 140, with the metal part in front of your eyes...watching the metal part ..not the face with numbers, the other face.... this way,. with the leads pointing down, from left to rigth you have base, colector and emitter.
The 2SC5200 and complementary...with the face with numbers in front of you.... in such way you can read the numbers.... leads pointed down... left to rigth is base , colector and emitter.
BC546 and other small folks... leads pointing down.... face in front of your eyes, in such a condition you can read the numbers, from left to rigth you have colector, base and emitter.
Diodes...the black strip you have identify the position you have into your zener diode that represents the arrow direction.
This will be needed.... knowledge to measure resistances and to read the values on them
Also how to measure transistors and how to identify the leads.
How to measure resistances into the circuit... the rail resistances to ground and to positive or minus.
Good lenses to watch circuit very close... cleaning product to remove flux from the board, as this can confuse us a lot... and really a hard work.... and this only you can do.
regards,
Carlos
As you have parts blowing, for sure hard unballance of voltages and current are running into your amplifier.
I hope you are using the protective resistances in series with the rails...they are needed...to avoid burns.
You have to check all your transistors positions...if not assembled into wrong position, need to know the base lead, colector and emitter and need to measure each one of them to check if someone more is damaged.... inform if you know how to measure transistors and if you have the correct identification to all of them... say...base, colector and emitter leads.
You will need to check resistances, if values are the same into the schematic and the whole circuit for shorts...measuring resistances into the board with power off, searching for low resistances.
Resistance measurements from plus to minus... from plus to ground, and from minus to ground...and inverting you probe points will show problems too...and the rail you have something wrong.
Also, of course, you need to check your supply polarity..if the positive wire you are using is really positive...and so on...also to check if voltages are the same into positive rail and negative rail..same value with opposite polarities, of course.
I cannot do too much from Recife to your place...just to listen your problems and try to teach you methods to track defects..some of them already written.
VBE is a good idea of the stage sittuation.... measuring voltages from base to emitter will tell you if the unit is working fine in that stage you are measuring... the input circuit, base to emitter will be checked this way...voltages goes from 400 to 800 there...good when goes from 580 to 640 milivolts (my experience).
I can give you a voltage chart....but you will be on troubles to debug watching voltage charts...if not experienced will feel yourself lost... the better idea is to remove each transistor and measure out from the circuit, or to lift, at least 2 leads to measure.
The measurement is the diode position you have into your multimeters...start with the black lead into the base and them touch the red lead into the colector and after that into the emitter.
Now invert.... fix the red lead into the base... and them touch the black lead into the colector and after that into the emitter.
A good transistor will conduct in one polarity and will not conduct in the other...you will measure something near 600 into your digital multimeter into the diode position... the value can be different...the logics of polarities have to be obbeyed..if not...problems.
The damaged transistor normally present short circuit between leads.... you have no shorts, not low resistance into a transistor...so...the presence of short, not matter the lead is... shows the unit as damaged.
A good idea is to check from colector to emitter and repeating the same measurement with inverted polarities.
Use the bias adjustment i suggested.... 680 ohms fixed resistance in series with a 100 ohms trimpot.... watch the images in the previous posts...i have checked this now...real life... i have made the amplifier once again, with the schematic values and adjusted perfectly and easy.
Burns means errors...and now all transistors need to be checked...also electrolitic condenser polarities will need check.
The BD139 and 140, with the metal part in front of your eyes...watching the metal part ..not the face with numbers, the other face.... this way,. with the leads pointing down, from left to rigth you have base, colector and emitter.
The 2SC5200 and complementary...with the face with numbers in front of you.... in such way you can read the numbers.... leads pointed down... left to rigth is base , colector and emitter.
BC546 and other small folks... leads pointing down.... face in front of your eyes, in such a condition you can read the numbers, from left to rigth you have colector, base and emitter.
Diodes...the black strip you have identify the position you have into your zener diode that represents the arrow direction.
This will be needed.... knowledge to measure resistances and to read the values on them
Also how to measure transistors and how to identify the leads.
How to measure resistances into the circuit... the rail resistances to ground and to positive or minus.
Good lenses to watch circuit very close... cleaning product to remove flux from the board, as this can confuse us a lot... and really a hard work.... and this only you can do.
regards,
Carlos
Did you understand the bias adjustment? measure with ohmmeter from servo+ to - while adjusting bias trimpot. Value should be 3k, then you should be safe from overbiasing.
I agree with carlos, fastest way to test errors is to remove the transistors and check them with diode test on multimeter... one leg will conduct to two other legs only... will only work one way around... if it can conduct between other pins or when you swap the meter probes then it is faulty... the input transistors have never blown on mine, normaly error is with bd139 driver before output.
Also double check resistances etc...
When looking at silkscreen, the narrower side of the bd 139/40 is the front... also try to measure DC from ground to output for us, as it may point out some errors...
Don't feel bad, it took me days to get my first DX working... even after all was 100, I had fake toshiba transistors which were totaly ubstable.
I agree with carlos, fastest way to test errors is to remove the transistors and check them with diode test on multimeter... one leg will conduct to two other legs only... will only work one way around... if it can conduct between other pins or when you swap the meter probes then it is faulty... the input transistors have never blown on mine, normaly error is with bd139 driver before output.
Also double check resistances etc...
When looking at silkscreen, the narrower side of the bd 139/40 is the front... also try to measure DC from ground to output for us, as it may point out some errors...
Don't feel bad, it took me days to get my first DX working... even after all was 100, I had fake toshiba transistors which were totaly ubstable.
Good help Nordic, thanks, i think Razorback made his own boards
But your indications are fine..... the more normal is to find voltages, from base to emitter, that goes from 520 to 620 milivolts...this is what happens more normally into AB biased amplifiers... this is more normal and means good operation...also good sonics.
The other values, the low extreme of 400 or even 500 milivolts will make the amplifier switch on and off... this will introduce a lot of distortions.
The upper extreme.... near 700 milivolts and forcing the unit very hard with bigger voltage than that, from base to emitter, will drive the transistor near the saturation..so.... it will have a very small room to increasings..when audio current enters, you will have conditions to use the negative part of the audio to drive the unit to lower currrent...but the opposite is not the same... it will drive a little and will fast find saturation.
Listening...i found the best around 590 milivolts...for those small BCs we use.... for VAS i have found 605 milivolts as nice operational point.... the second one has sligtly bigger VBE.... going to 610 milivolts.
The differential, into the High Resolution II has 580 milivolts from base to emitter.
I hope those informs help.... i will produce voltage chart....but i think the remotion of parts is the fastest method...if you decide to be thinking to conclude, or realise, what is the guilty...the time spent will be bigger that the time you need to fix the unit three times!
So...we have the decision to be proud and decide to discover...wasting time or be clever and fix the damn thing as soon as possible.
regards,
Carlos
But your indications are fine..... the more normal is to find voltages, from base to emitter, that goes from 520 to 620 milivolts...this is what happens more normally into AB biased amplifiers... this is more normal and means good operation...also good sonics.
The other values, the low extreme of 400 or even 500 milivolts will make the amplifier switch on and off... this will introduce a lot of distortions.
The upper extreme.... near 700 milivolts and forcing the unit very hard with bigger voltage than that, from base to emitter, will drive the transistor near the saturation..so.... it will have a very small room to increasings..when audio current enters, you will have conditions to use the negative part of the audio to drive the unit to lower currrent...but the opposite is not the same... it will drive a little and will fast find saturation.
Listening...i found the best around 590 milivolts...for those small BCs we use.... for VAS i have found 605 milivolts as nice operational point.... the second one has sligtly bigger VBE.... going to 610 milivolts.
The differential, into the High Resolution II has 580 milivolts from base to emitter.
I hope those informs help.... i will produce voltage chart....but i think the remotion of parts is the fastest method...if you decide to be thinking to conclude, or realise, what is the guilty...the time spent will be bigger that the time you need to fix the unit three times!
So...we have the decision to be proud and decide to discover...wasting time or be clever and fix the damn thing as soon as possible.
regards,
Carlos
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I will be very happy (very proud and snobbish) to receive the alert in advance
related the last moments when my dear constructors will be near to finish adjustments and start to listen the High Resolution II
I was listening today, and i think you will feel so happy with it that you will have the need to give a kiss into uncle Charlie's face.
So....please, tell me in advance...i will shave myself and use a nice perfume...ahahahahaha
By the way...no oscilations...i have removed the 150pF capacitors and no oscilations.... mine is using 47pf...but start with 150pf and make your own tests going down.
I have used the treble boost... i like it...but cannot be used with some musics...you will perceive that will saturate..of course will do that if the recording level, or trebles, is too much high... even this way produce nice harmonic distortion...nice effect (or defect)
A hell difficult to oscilate folks...very reliable.
Wait some minutes to adjust... and make retouches after adjustments..because the circuit start with higher off set and goes down by itself... the stand by current can be adjusted first time and them give a hard time to the amplifier to make it work hot... then reduce your bias setting to half way... referenced to your starting biasing point and the hot biasing current... do not reduce too much, because when cold you may have low level distortions.... if you want to take some small risks.... to keep good sonics... adjust cold and let the bias go higher when hot... accept as normal and relax do not tweaking that anymore.
I have drive it to distortion.... for time enougth to bother my neigthboors... over 4 ohms.... the VAS do not need protection... i could not burn it.
Use small heatsink to VAS bigger transistor, the BD139.
Install heatsinks to drivers and small ones, if needed, into your rail regulators... this will depend the voltage reduction there..if 5 volts..better to use a small piece of copper soldered into the transistor, or other kind of heatsink....if the reduction, adjusted by you using LED in series with the zener, was fixed to only 2.5 volts...then, do not use heatsink there.
regards,
Carlos
related the last moments when my dear constructors will be near to finish adjustments and start to listen the High Resolution II
I was listening today, and i think you will feel so happy with it that you will have the need to give a kiss into uncle Charlie's face.
So....please, tell me in advance...i will shave myself and use a nice perfume...ahahahahaha
By the way...no oscilations...i have removed the 150pF capacitors and no oscilations.... mine is using 47pf...but start with 150pf and make your own tests going down.
I have used the treble boost... i like it...but cannot be used with some musics...you will perceive that will saturate..of course will do that if the recording level, or trebles, is too much high... even this way produce nice harmonic distortion...nice effect (or defect)
A hell difficult to oscilate folks...very reliable.
Wait some minutes to adjust... and make retouches after adjustments..because the circuit start with higher off set and goes down by itself... the stand by current can be adjusted first time and them give a hard time to the amplifier to make it work hot... then reduce your bias setting to half way... referenced to your starting biasing point and the hot biasing current... do not reduce too much, because when cold you may have low level distortions.... if you want to take some small risks.... to keep good sonics... adjust cold and let the bias go higher when hot... accept as normal and relax do not tweaking that anymore.
I have drive it to distortion.... for time enougth to bother my neigthboors... over 4 ohms.... the VAS do not need protection... i could not burn it.
Use small heatsink to VAS bigger transistor, the BD139.
Install heatsinks to drivers and small ones, if needed, into your rail regulators... this will depend the voltage reduction there..if 5 volts..better to use a small piece of copper soldered into the transistor, or other kind of heatsink....if the reduction, adjusted by you using LED in series with the zener, was fixed to only 2.5 volts...then, do not use heatsink there.
regards,
Carlos
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