Hello Dnilsson.
I've encountered problems like these many times through the years. The first thing to do is recheck your circuit boards to make sure you have good solder connections. Other obvious things that can cause this problem that I've seen are stray RF being picked up because the top is not on the unit. Also with some circuits hooking scope ground to the circuit ground can cause this problem. Lastly of course the capacitor across Q5 seems like a good solution.
Hope some of these pointers help.
Steve Dunlap
I've encountered problems like these many times through the years. The first thing to do is recheck your circuit boards to make sure you have good solder connections. Other obvious things that can cause this problem that I've seen are stray RF being picked up because the top is not on the unit. Also with some circuits hooking scope ground to the circuit ground can cause this problem. Lastly of course the capacitor across Q5 seems like a good solution.
Hope some of these pointers help.
Steve Dunlap
More experiments...
Hi,
Carlos, Steve, thanks for your suggestions. I worked on this a little more last night, since I was able to get a stable bias at 60mA with no oscillations I decided to see what impact the leads that I'm using to hook up the 10ohm resistors in place for the fuses had. With the bias stable I removed the 10 ohm resistors and put the fuses back. That did not go so well though. Transistor Q9 broke and went into short circuit which brought Z3A and Z3B down as well... DC was now coming out of the unit instead.
I have a theory though, I have used 4700uF in position C4 and C7 according to Nordics BOM. Looking into the regulation circuit that Q9 and Q8 forms I'm not sure these regulators actually are stable for this high amount of capacitance in position C4 and C7. When verifying DC/DC regulators at work we verify the phase margin for the regulator and sometimes we need to adjust the feedback if we have a lot of decoupling caps on a digital board in order to keep the regulator stable and with adequate phase margin. Looking at the zener regulator together with Q9 and Q8 in not sure this arrangement is actually stable with this much capacitance in place at C4 and C7? I will try to replace C4 and C7 with 220uF instead and repair the broken components. Can anyone confirm stable operation with 4700uF at C4 and C7? I have rought +/- 42V coming in to the unit as well when only biased, Z3A and Z3B are left at 16+16V = 32V. There is roughly 10V across Q9 and Q8.
Steve, both channels are acting the same way so I think that puts solder connections at a low probability. I will evaluate your other suggestions when the unit is repaired!
Thanks
Daniel
Hi,
Carlos, Steve, thanks for your suggestions. I worked on this a little more last night, since I was able to get a stable bias at 60mA with no oscillations I decided to see what impact the leads that I'm using to hook up the 10ohm resistors in place for the fuses had. With the bias stable I removed the 10 ohm resistors and put the fuses back. That did not go so well though. Transistor Q9 broke and went into short circuit which brought Z3A and Z3B down as well... DC was now coming out of the unit instead.
I have a theory though, I have used 4700uF in position C4 and C7 according to Nordics BOM. Looking into the regulation circuit that Q9 and Q8 forms I'm not sure these regulators actually are stable for this high amount of capacitance in position C4 and C7. When verifying DC/DC regulators at work we verify the phase margin for the regulator and sometimes we need to adjust the feedback if we have a lot of decoupling caps on a digital board in order to keep the regulator stable and with adequate phase margin. Looking at the zener regulator together with Q9 and Q8 in not sure this arrangement is actually stable with this much capacitance in place at C4 and C7? I will try to replace C4 and C7 with 220uF instead and repair the broken components. Can anyone confirm stable operation with 4700uF at C4 and C7? I have rought +/- 42V coming in to the unit as well when only biased, Z3A and Z3B are left at 16+16V = 32V. There is roughly 10V across Q9 and Q8.
Steve, both channels are acting the same way so I think that puts solder connections at a low probability. I will evaluate your other suggestions when the unit is repaired!
Thanks
Daniel
Those enormous condensers are not needed
Using rail regulators you have the capacitance multiplier efect when using condensers from base to ground...also you have electronic filtering...we can call ripple rejection and some stabilization of voltage.... 220uf is already a very good value to be there... current is not so big into first stage and zener.
I was against those big condensers since the early beginning.... they are needed into the Dx Standard, because does not use rail regulators... but we have to accept people's freedom to try ideas.
Surge of current can be very big there, when you power on...and the extra capacitance will not help.. the regulators already do a great job.
If you decide to keep your "whale" condensers there, substitute the rail regulator transistors by a powerfull units, alike TIP41 and TIP42... those ones can hold 6 amperes continuous and surges of 4 times this current.... when the BD139 will hold only 4 amperes into the surge.
I do think they are ugly too (big condensers).... looks alike a small boat with both trade center buidings atop of them... there's a serious sthetical problems there.... or someone with 8 meters diameter hat!...nothing nice to a small board.
Even the input ones.... the ones you have were your supply power enters the audio power board, does not need to be big...as wire cables are short and normally overkilled by our audiophile tradition...resistance is very low there...so...it is alike you have the supply filter condensers assembled into the supply...the power supply cable beeing so short, so low resistance means the same thing....so...we already have a lot o capacitance into the power amplifier input...as power amplifier power input terminals and power supply output terminals are almost the same thing, electrically speaking.
You know...if you wanna know...well.... really....there's a problem with Nordic...he is a very handsome man... his wife is beautifull.. alike a movie star.... you know.... we need some ballance in our life... he needed that ugly thing there to compensate all the beauty he has inside his home.... everyday he watch himself into the mirror or when he watch his wife (gorgeous, wonderfull lady..almost spectacular beautifull woman).... ahahahaha!... he will not answer or read that..he is busy with his new house...so i can go buzzing.... his condensers are so huge the are in excess to the board size..ahahaha..they go out from the board!
Good luck with your research.
regards,
Carlos
Using rail regulators you have the capacitance multiplier efect when using condensers from base to ground...also you have electronic filtering...we can call ripple rejection and some stabilization of voltage.... 220uf is already a very good value to be there... current is not so big into first stage and zener.
I was against those big condensers since the early beginning.... they are needed into the Dx Standard, because does not use rail regulators... but we have to accept people's freedom to try ideas.
Surge of current can be very big there, when you power on...and the extra capacitance will not help.. the regulators already do a great job.
If you decide to keep your "whale" condensers there, substitute the rail regulator transistors by a powerfull units, alike TIP41 and TIP42... those ones can hold 6 amperes continuous and surges of 4 times this current.... when the BD139 will hold only 4 amperes into the surge.
I do think they are ugly too (big condensers).... looks alike a small boat with both trade center buidings atop of them... there's a serious sthetical problems there.... or someone with 8 meters diameter hat!...nothing nice to a small board.
Even the input ones.... the ones you have were your supply power enters the audio power board, does not need to be big...as wire cables are short and normally overkilled by our audiophile tradition...resistance is very low there...so...it is alike you have the supply filter condensers assembled into the supply...the power supply cable beeing so short, so low resistance means the same thing....so...we already have a lot o capacitance into the power amplifier input...as power amplifier power input terminals and power supply output terminals are almost the same thing, electrically speaking.
You know...if you wanna know...well.... really....there's a problem with Nordic...he is a very handsome man... his wife is beautifull.. alike a movie star.... you know.... we need some ballance in our life... he needed that ugly thing there to compensate all the beauty he has inside his home.... everyday he watch himself into the mirror or when he watch his wife (gorgeous, wonderfull lady..almost spectacular beautifull woman).... ahahahaha!... he will not answer or read that..he is busy with his new house...so i can go buzzing.... his condensers are so huge the are in excess to the board size..ahahaha..they go out from the board!
Good luck with your research.
regards,
Carlos
This audio oscilator is very good folks
I have downloaded, for free, some years ago.... was into a Simulator Software site...offered also Scopes and other things connected to simulation and computer generated instruments.
Size is big...more than 20 Megabytes.
I hope you will find...it is almost perfect....no advantage to have a real one... this one does the job.
regards,
Carlos
.....................................................................................................
Dx amplifiers put out full power, into 4 ohms and 8 ohms speakers (not loads), reproducing full power 1 hertz sinusoidal tone..without clicks or pops, without noises during crossover and without hum from the supply...no ripple...no dirty sound.
Do not trust me.... trust into the amplifier.... the one has spirit...it is a happy reliable amplifier..hard to kill...good sounding...tested..for free.... and from our beloved forum.
Knowledge to create them came from the forum... with some help from Hugh Dean and Graham Maynard too.
regards,
Carlos
I have downloaded, for free, some years ago.... was into a Simulator Software site...offered also Scopes and other things connected to simulation and computer generated instruments.
Size is big...more than 20 Megabytes.
I hope you will find...it is almost perfect....no advantage to have a real one... this one does the job.
regards,
Carlos
.....................................................................................................
Dx amplifiers put out full power, into 4 ohms and 8 ohms speakers (not loads), reproducing full power 1 hertz sinusoidal tone..without clicks or pops, without noises during crossover and without hum from the supply...no ripple...no dirty sound.
Do not trust me.... trust into the amplifier.... the one has spirit...it is a happy reliable amplifier..hard to kill...good sounding...tested..for free.... and from our beloved forum.
Knowledge to create them came from the forum... with some help from Hugh Dean and Graham Maynard too.
regards,
Carlos
Attachments
Measurements...
Hi,
So I got the unit repaired, and made some modification. Referring to this schematics
, C4/C7 are replaced with 220uF and after making this modification I had no problems powering on any longer.
The oscillations are still present though, but I have made some improvements. The issue is harder to trigger when powering the amp directly without using 10ohm resistors instead of fuses in the PSU, but it is still present.
I have concluded that the mains ground is not part of the problem, I also replaced C26/C29 with 470uF instead of 8200uF but that was not related either. The oscillations seems related to the zobel network somehow, grounding of the zobel network seems critical. Right now I have a thick wire running to the GND spade of the amp, but I have also tried bringing it to the common ground where PSU, speaker, etc ground is joined but that made the oscillations worse. What I'd like to focus on is figuring out how the oscillations work, comparing the output and the feedback input signal. If I add C21 to the board (it is not present in the schematics present on dxamp.com for some reason), the oscillations occur more or less directly after power-on.
With C21 present, there are oscillations on the output of roughly 1500mV peak-to-peak on the output at around 6MHz. Probing the circuit in this condition I can detect that there are no oscillations at either side of capacitors C6 and C9 so these points are "ok" and stable.
In the following 3 pictures channel 1 is on the output and channel 2 is probing the various locations, I don't have a way to get the scope shots from the scope directly so I just took a picture with the camera. Note that C21 is in place here, so there are large oscillations on the output.
R10/R11 on channel 2
Emitter of Q1 on channel 2
Emitter of Q2 on channel 2
My conclusion from this is that voltage regulation on all zener locations are ok but that the whole Q1/Q2, driver and output voltage are moving up and down for some reason.
Couple of questions:
Could this be related to the DC offset level regulation that is not stable for some reason?
Why was C21 removed from Nordic's schematics? Seems like it was in place at one point, was it removed because it created these kinds of problems?
The reason I have been making these measurements with C21 in place is because it makes the issue easier to trigger for measurements. But the issue is still there when running a sinewave through the amp without C21 in place.
Sine output without C21
Look at the bottom portion of the sinewave, the small ringing there is the same ringing that is present with the amp just biased.
For all experiments above I have added another 220pF to C18 in order to secure that the amp is not oscillating because of a to low value on C18.
What conclusions could be drawn for the above measurements? Any ideas for further experiments?
Regards
Daniel
Hi,
So I got the unit repaired, and made some modification. Referring to this schematics
, C4/C7 are replaced with 220uF and after making this modification I had no problems powering on any longer.
The oscillations are still present though, but I have made some improvements. The issue is harder to trigger when powering the amp directly without using 10ohm resistors instead of fuses in the PSU, but it is still present.
I have concluded that the mains ground is not part of the problem, I also replaced C26/C29 with 470uF instead of 8200uF but that was not related either. The oscillations seems related to the zobel network somehow, grounding of the zobel network seems critical. Right now I have a thick wire running to the GND spade of the amp, but I have also tried bringing it to the common ground where PSU, speaker, etc ground is joined but that made the oscillations worse. What I'd like to focus on is figuring out how the oscillations work, comparing the output and the feedback input signal. If I add C21 to the board (it is not present in the schematics present on dxamp.com for some reason), the oscillations occur more or less directly after power-on.
With C21 present, there are oscillations on the output of roughly 1500mV peak-to-peak on the output at around 6MHz. Probing the circuit in this condition I can detect that there are no oscillations at either side of capacitors C6 and C9 so these points are "ok" and stable.
In the following 3 pictures channel 1 is on the output and channel 2 is probing the various locations, I don't have a way to get the scope shots from the scope directly so I just took a picture with the camera. Note that C21 is in place here, so there are large oscillations on the output.
R10/R11 on channel 2
Emitter of Q1 on channel 2
Emitter of Q2 on channel 2
My conclusion from this is that voltage regulation on all zener locations are ok but that the whole Q1/Q2, driver and output voltage are moving up and down for some reason.
Couple of questions:
Could this be related to the DC offset level regulation that is not stable for some reason?
Why was C21 removed from Nordic's schematics? Seems like it was in place at one point, was it removed because it created these kinds of problems?
The reason I have been making these measurements with C21 in place is because it makes the issue easier to trigger for measurements. But the issue is still there when running a sinewave through the amp without C21 in place.
Sine output without C21
Look at the bottom portion of the sinewave, the small ringing there is the same ringing that is present with the amp just biased.
For all experiments above I have added another 220pF to C18 in order to secure that the amp is not oscillating because of a to low value on C18.
What conclusions could be drawn for the above measurements? Any ideas for further experiments?
Regards
Daniel
Fake output transistors... I read a lot about that in this thread, and I tried to avoid getting those fakes ones. But how to tell if I have the original ones?
I bought mine from Digikey, thought I had read somewhere that digikey guarantees that they only buy directly from Toshiba. Is there a way to tell for sure?
I bought mine from Digikey, thought I had read somewhere that digikey guarantees that they only buy directly from Toshiba. Is there a way to tell for sure?
Yes my dear... as i told you...i already forgot details...i have made many other
before this one...and C21 was supressed because it is a problem creator!...so...you got it!
I have not watched into waveform monitor...i felt sound strange with the capacitor and have decide to remove..also the adjustment was strange with the condenser in place
It seems to me you have fake transistors too.
Into the long thread we had someone that made testing and have posted waveforms...and all fine.
We had problems with C21.... and it was removed.... people that was building had those informations into the thread and also into the group buy...it seems you have not readed the thread.
So.... you may find another bug already discovered.... what about to stop tweaking and read a little...you see... this C21 was already supressed...i am terrible sorry...i could not remember.
And i think there are other things posted.... man!... this had much more than a year... was more than an year ago!...i have 57 years old...memory is not perfect anymore.
If you decide not to read...you will re-discover, step by step, the powder without smoke.... if you appreciate this way.... then go ahead.
regards,
Carlos
before this one...and C21 was supressed because it is a problem creator!...so...you got it!
I have not watched into waveform monitor...i felt sound strange with the capacitor and have decide to remove..also the adjustment was strange with the condenser in place
It seems to me you have fake transistors too.
Into the long thread we had someone that made testing and have posted waveforms...and all fine.
We had problems with C21.... and it was removed.... people that was building had those informations into the thread and also into the group buy...it seems you have not readed the thread.
So.... you may find another bug already discovered.... what about to stop tweaking and read a little...you see... this C21 was already supressed...i am terrible sorry...i could not remember.
And i think there are other things posted.... man!... this had much more than a year... was more than an year ago!...i have 57 years old...memory is not perfect anymore.
If you decide not to read...you will re-discover, step by step, the powder without smoke.... if you appreciate this way.... then go ahead.
regards,
Carlos
I'm sorry...
... I think I must have got you all confused here. I have read most of this thread, and I have not followed any old instructions for building this amp as far as I know.
Some facts:
1. I have built to amp according to these schematics and with PCBs from dxamp.com:
https://www.dxamp.com/images/DxHRII_v.F_brd.pdf
I believe these schematics contain all the tweaks presented in this thread, correct me if I'm wrong.
2. I refer to Greg's schematics because Carlos you seemed to be more familiar with the reference designators on this schematics a couple posts back when we started talking about specific components in the design. So I just wanted to make it easier for you and only refer to the same set of schematics as you were referring to.
3. When building the amp according to Nordic's schematics, and after making some ground and power supply improvements in the design the amp is basically stable. I can however, at certain temperatures and at certain power level, produce a slight ringing in the output which seems to be related to the same problem as the one I originally posted which is an oscillation in the 5-15MHz range. This was the last picture in my previous post above.
4. Since it is hard to trigger this "problem" (if you call it a problem) with the slight ringing in the sine waveform I wanted to temporarily make the problem worse in order to make it easier to troubleshoot. Since I had found in the past that C21 from Greg's older schematics made the problem worse I added this cap to the design temporarily just for measurement purposes. The idea behind this is to try to measure how the oscillation works by comparing the output signal with the phase of the feedback signal to locate the oscillator. With C21 in place the oscillation happens a lot easier and makes it easier to measure. I have not succeeded here, mostly because I don't fully understand how the input stage was designed to work but I'm still learning the design. The idea behind the lengthly post above was to try to gain more understanding in this area of measurements with C21 temporarily in place, but I think I failed to convey that. Sorry about that. I'm not expecting to be able to get a stable amp with C21 in place, just using it temporarily to gain knowledge how this oscillation works.
5. I was made aware that fake output transistors might cause issues like these, and Carlos you also seemed to suggest I might have fake ones. How do I know for sure? Are Digikey (where I bought mine) known to sell fake Toshiba transistors?
Did that clear anything up? I hope so... Thanks for all the help so far!
Regards
Daniel
... I think I must have got you all confused here. I have read most of this thread, and I have not followed any old instructions for building this amp as far as I know.
Some facts:
1. I have built to amp according to these schematics and with PCBs from dxamp.com:
https://www.dxamp.com/images/DxHRII_v.F_brd.pdf
I believe these schematics contain all the tweaks presented in this thread, correct me if I'm wrong.
2. I refer to Greg's schematics because Carlos you seemed to be more familiar with the reference designators on this schematics a couple posts back when we started talking about specific components in the design. So I just wanted to make it easier for you and only refer to the same set of schematics as you were referring to.
3. When building the amp according to Nordic's schematics, and after making some ground and power supply improvements in the design the amp is basically stable. I can however, at certain temperatures and at certain power level, produce a slight ringing in the output which seems to be related to the same problem as the one I originally posted which is an oscillation in the 5-15MHz range. This was the last picture in my previous post above.
4. Since it is hard to trigger this "problem" (if you call it a problem) with the slight ringing in the sine waveform I wanted to temporarily make the problem worse in order to make it easier to troubleshoot. Since I had found in the past that C21 from Greg's older schematics made the problem worse I added this cap to the design temporarily just for measurement purposes. The idea behind this is to try to measure how the oscillation works by comparing the output signal with the phase of the feedback signal to locate the oscillator. With C21 in place the oscillation happens a lot easier and makes it easier to measure. I have not succeeded here, mostly because I don't fully understand how the input stage was designed to work but I'm still learning the design. The idea behind the lengthly post above was to try to gain more understanding in this area of measurements with C21 temporarily in place, but I think I failed to convey that. Sorry about that. I'm not expecting to be able to get a stable amp with C21 in place, just using it temporarily to gain knowledge how this oscillation works.
5. I was made aware that fake output transistors might cause issues like these, and Carlos you also seemed to suggest I might have fake ones. How do I know for sure? Are Digikey (where I bought mine) known to sell fake Toshiba transistors?
Did that clear anything up? I hope so... Thanks for all the help so far!
Regards
Daniel
Try other transistors dear Daniel... it is all right between us
no problems at all.
You see....no one has the way to make a non destructive testing to have transistor parameters.... of course no one wants to destroy them to know, for instance, if they can really hold 10 amperes...or if can really dissipate 150 watts!
So..because of that..we do not know datasheet with destructive testings..have to go to the limits, and wait it burn to be sure it cannot dissipate that power or cannot hold that current or cannot work with that voltage!
Also, even datasheet say can dissipate 150 watts IF you keep case into 25 degrees celsius..ahahahahah!
Try another pair into the output...even lower power units...something you trust...also as drivers.... do not produce power.... just measure your signals into scope and observe the bias and thermal issues.
There are hundreds of threads talking about fake ones... and each one of them show some signs "they think" indicates the fake ones.... but we cannot have sure.
I know, facing those fake ones.... they use to be low power units, higher gain units..higher frequency units..some cheaper units that receive new numbers as will be an advantage to seel them as 150 watts units when they are not.
2SC5200 and 2SA1943 use to have gain from 70 to 100..... so... if you find 140 of gain.... you should start to feel some suspectious about the higher gain unit.
Yep...i had problems.... a lot of them...i was learning how to conduct a thread..also Nico was learning...and Greg was the only one was professional inside this group.... i have not informed all i should to Greg.... i used to publish into the forum.... as he had not received direct orders to change things he keep the things the way the are waiting for my mail about....and i have failed with him several times.
We had numbers into schematic..part numbers... then Nordic made other numbers as he have prepared the board...then he suggested "others" to change number...or i have asked him to change....well... i know that there are different part numbers....a big mess was made there into the HRII....i am sorry very much..but only having schematics, without read that enormous thread you may face some problems... i cannot remember all the stuff...i have forgot the C21 creates a big mess into the signal...was something perceived by Klaas Veenstra into the Dx Standard ealier amplifier..he found also some strange signal..small signal supperposed to the waveform.
Related different schematics i had problems with that.... what should be the one to follow other guys schematic part numbers?... one would say i was the first..so...my numbers have to be the ones!...other will say... i have made the board..and the numbers follow board numbers...so... it is more reasonable to keep my numbers as the main ones.... the result is the one you have observed... 2 part numbers... i think they were not fixed... not your problem but it is not easy to conduct a thread..in special when you have more than one guy cooperating.
regards and be happy.
Carlos
no problems at all.
You see....no one has the way to make a non destructive testing to have transistor parameters.... of course no one wants to destroy them to know, for instance, if they can really hold 10 amperes...or if can really dissipate 150 watts!
So..because of that..we do not know datasheet with destructive testings..have to go to the limits, and wait it burn to be sure it cannot dissipate that power or cannot hold that current or cannot work with that voltage!
Also, even datasheet say can dissipate 150 watts IF you keep case into 25 degrees celsius..ahahahahah!
Try another pair into the output...even lower power units...something you trust...also as drivers.... do not produce power.... just measure your signals into scope and observe the bias and thermal issues.
There are hundreds of threads talking about fake ones... and each one of them show some signs "they think" indicates the fake ones.... but we cannot have sure.
I know, facing those fake ones.... they use to be low power units, higher gain units..higher frequency units..some cheaper units that receive new numbers as will be an advantage to seel them as 150 watts units when they are not.
2SC5200 and 2SA1943 use to have gain from 70 to 100..... so... if you find 140 of gain.... you should start to feel some suspectious about the higher gain unit.
Yep...i had problems.... a lot of them...i was learning how to conduct a thread..also Nico was learning...and Greg was the only one was professional inside this group.... i have not informed all i should to Greg.... i used to publish into the forum.... as he had not received direct orders to change things he keep the things the way the are waiting for my mail about....and i have failed with him several times.
We had numbers into schematic..part numbers... then Nordic made other numbers as he have prepared the board...then he suggested "others" to change number...or i have asked him to change....well... i know that there are different part numbers....a big mess was made there into the HRII....i am sorry very much..but only having schematics, without read that enormous thread you may face some problems... i cannot remember all the stuff...i have forgot the C21 creates a big mess into the signal...was something perceived by Klaas Veenstra into the Dx Standard ealier amplifier..he found also some strange signal..small signal supperposed to the waveform.
Related different schematics i had problems with that.... what should be the one to follow other guys schematic part numbers?... one would say i was the first..so...my numbers have to be the ones!...other will say... i have made the board..and the numbers follow board numbers...so... it is more reasonable to keep my numbers as the main ones.... the result is the one you have observed... 2 part numbers... i think they were not fixed... not your problem but it is not easy to conduct a thread..in special when you have more than one guy cooperating.
regards and be happy.
Carlos
Attachments
Transformer centre tap grounding
Evening all (UK time!).
I'm getting close to wiring up the power for the HRII, and just doing a bit of background 'reassurance' reading on dual primary / dual secondary transformers.
Hmm, not as reassuring as I wanted! I've come across a few audio and music sites (here for example) that suggest that a dual secondary can have the centre taps just soldered and taped up, and not grounded, when using a rectified power supply. I was planning to send the secondary centre taps to the chassis ground.
I've also read that the same can be done to the dual primaries - just solder the centre tap leads together and insulate them.
It's my power supply naivety kicking in again, but this makes me a bit uncomfortable - and I thought this the best place to turn for advice.
For info, I have a dual primary / dual secondary transformer, 115-0-115 to 25-0-25, 225 VAC.
Cheers,
Darren
Evening all (UK time!).
I'm getting close to wiring up the power for the HRII, and just doing a bit of background 'reassurance' reading on dual primary / dual secondary transformers.
Hmm, not as reassuring as I wanted! I've come across a few audio and music sites (here for example) that suggest that a dual secondary can have the centre taps just soldered and taped up, and not grounded, when using a rectified power supply. I was planning to send the secondary centre taps to the chassis ground.
I've also read that the same can be done to the dual primaries - just solder the centre tap leads together and insulate them.
It's my power supply naivety kicking in again, but this makes me a bit uncomfortable - and I thought this the best place to turn for advice.
For info, I have a dual primary / dual secondary transformer, 115-0-115 to 25-0-25, 225 VAC.
Cheers,
Darren
AndrewT said:
Thanks Andrew. My feelings exactly - I certainly won't be switching anything on until I'm sure.
The labelling doesn't tell me much - the transformer wiring diagram for both sides looks identical, showing two primaries of 115 and two secondaries of 25. This might match with what you're saying, but again my lack of knowledge is not at all a help here.
It's a new transformer, so I'm guessing there's some standard colour coding - primary wiring starts with blue and ends with brown, with grey and violet between. Secondary wiring starts with black and ends with yellow, with red and orange in between. This correlates with a few earlier posts in this thread about grounding the secondary centre tap.
Cheers,
Darren
Measure resistances to identify your two coils
of course if you have two independent coils.... 4 wires.
So you gonna have "A"... will have "B" as the first coil....and will have "C" and "D" as the second coil
To use into 220 volts you have to make them serial....so... try to join "B" and "C" while you have "A" and "B" powered.. be carefull to touch only wire insulators and not wire tips.
If connecting you will not have enormous flash you have found the correct phase to them.... when out of phase the surge of current when you touch "B" and "C" together is huge.
Also you can use an AC amperometer... this way will be better.... the smaller reading will be the correct phasing.
Well..for sure this is not safe to do...maybe to ask someone more experienced about transformers to phase it to you.
If you gonna use 115 volts then "A" goes to "C" and "B" goes connected to "D"........ OR..... "A" goes to "D" and "B" goes connected to C.
You have first of all to identify the coils..and to baptise a letter to each wire..then you can start to tweak..but better to find someone have already made that several times.
regards,
Carlos
of course if you have two independent coils.... 4 wires.
So you gonna have "A"... will have "B" as the first coil....and will have "C" and "D" as the second coil
To use into 220 volts you have to make them serial....so... try to join "B" and "C" while you have "A" and "B" powered.. be carefull to touch only wire insulators and not wire tips.
If connecting you will not have enormous flash you have found the correct phase to them.... when out of phase the surge of current when you touch "B" and "C" together is huge.
Also you can use an AC amperometer... this way will be better.... the smaller reading will be the correct phasing.
Well..for sure this is not safe to do...maybe to ask someone more experienced about transformers to phase it to you.
If you gonna use 115 volts then "A" goes to "C" and "B" goes connected to "D"........ OR..... "A" goes to "D" and "B" goes connected to C.
You have first of all to identify the coils..and to baptise a letter to each wire..then you can start to tweak..but better to find someone have already made that several times.
regards,
Carlos
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you won't last forever if you carry on misreading like that.Forever13 said:
Bl, Br, Gr, Vi tells us that you have a dual primary transformer. i.e 115-0, 115-0.
Do you remember what the Live and Neutral colours are on our UK mains supplies?
Bl & Br.
Connect the Vi & Gr to a terminal in a 3bay terminal strip.
Connect the Bl to a terminal and common it up with the Bl Neutral wire from your mains input cable.
Connect the Br to the third terminal and run this back to the equipment switch. Now run from the switch to the mains fuse and finally to the Br from the mains input cable. If your switch is a two pole mains switch then insert the spare pole in the Neutral line between the mains cable and the Neutral in the 3bay terminal strip.
Do those "unknown" colours make sense now?
Take all four secondaries to separate terminals in a 4bay terminal strip.
Take the mains input cable Grn/Yel direct to a bolted connection to your chassis. Add a little Vaseline to delay corrosion and bolt the connection up tight. DO NOT ever remove this Permanent Safety Earth.
Final bit of advice:
Build up a mains light bulb tester and use it to first time power up every new project you build and use it again EVERY time you modify any of your equipment.
Safe working and live "forever13"
Try to find someone more experienced than you are
at least about transformers... the one have made that several times makes that fast and in a very safe way.
You see... i am alive...i have never died and i have made that hundred times (at least) in my life!...... but, forum management does not like people working with high voltages... it is very unsafe.
Well... i did that several times... forum moderators (some of them) have not even born to tell me this is dangerous.... so...without the advise i could survive...maybe a miracle!
By the way.... have you asked something to Mr Andrew T...i can see, despite i do not read his mails, he is around.
He may have constructed something alike.... as he is trying to help you.
regards,
at least about transformers... the one have made that several times makes that fast and in a very safe way.
You see... i am alive...i have never died and i have made that hundred times (at least) in my life!...... but, forum management does not like people working with high voltages... it is very unsafe.
Well... i did that several times... forum moderators (some of them) have not even born to tell me this is dangerous.... so...without the advise i could survive...maybe a miracle!
By the way.... have you asked something to Mr Andrew T...i can see, despite i do not read his mails, he is around.
He may have constructed something alike.... as he is trying to help you.
regards,
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AndrewT said:
It's that very thought that makes me try to learn more about power supplies - but trying to learn via the internet is rarely the best way of doing things (I know this from my own world of work, amongst other things running a major UK business forum).
Of course I know my blue from my brown - I also understand the concept of transformer windings...however the terminology, notation and construction of these things doesn't come easy to the beginner - and it's even harder to explain my own misunderstandings in plain text on a forum.
I wouldn't say misreading so much as not explaining myself very well, and also asking for a good bit of advice along the way - Andrew, your explanation was very useful indeed, thank you.
Hi Andrew - I've drawn a layout to show what I'd had planned before posting earlier (and no doubt causing alarm!). I've tried to read up on this, and it was only seeing that post on another forum that got me thinking about the centre taps. Isn't this layout right? (earth being a bare metal connection to the chassis that's also shared by the PSU ground, amp power & signal grounds and ground for the speaker output?)
I assume you mean the other way round, Brown live and Blue neutral?
(sorry, couldn't help that one)
Thanks again for your help and patience on this.
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Hi Carlos - I'll certainly find someone local to help me out before frying myself, the cat, the house, next door...
I assume you mean the other way round, Brown live and Blue neutral?
(sorry, couldn't help that one)Thanks again for your help and patience on this.
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Hi Carlos - I'll certainly find someone local to help me out before frying myself, the cat, the house, next door...
For Italian people, or to people that can read in Italian
Nuova Elettronica Audio Handbook.
come to my mail and i will be able to inform you how to download the entire book.
It is a PDF, color images, many amplifiers and 65 Megabytes size hosted into Easy Share.
panzertoo@yahoo.com
Carlos
.......................................................................................................
Everything fine forever...you can count on me forever and ever.
relax and be happy.
regards,
Carlos
Nuova Elettronica Audio Handbook.
come to my mail and i will be able to inform you how to download the entire book.
It is a PDF, color images, many amplifiers and 65 Megabytes size hosted into Easy Share.
panzertoo@yahoo.com
Carlos
.......................................................................................................
Everything fine forever...you can count on me forever and ever.
relax and be happy.
regards,
Carlos
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