So naughty. You should be using that time to catch up on Martha Stewart's Living.
And what's with the barber shop? You're a caveman! You should go to one of those unisex hair shops. Let the stylist guess if you're a man or a woman. 😀 Be politically correct now.
And what's with the barber shop? You're a caveman! You should go to one of those unisex hair shops. Let the stylist guess if you're a man or a woman. 😀 Be politically correct now.
You would be surprised how technical my wife's clothes sewing magazines have become with intricated patterns not unlike 10-layer PCBs.
Concerning transformers, they did not make it into my two last amp builds where I preferred to use SMPS. One of them class A 39W.
Yeah sewing and embroidery are pretty technical. Not the typical glossy used as pastime when one has nothing to do. You managed to find one of the rare yellow sheep in the flock and to defend the flock! Chapeau.
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Per that other thread (post 28) it looks like there is a thermal cutoff in the transformer. This could be a device wound in series with the primary against the core or (and I have seen this done) a single turn of lighter gauge wire in series with the primary winding. This used to be done in the 80’s and was typical of some wall wart designs. There’s likely not much ventilation inside a speaker box.
My 2 cents.
My 2 cents.
A thousand pardons, please.
Just tell me your preferred pronouns and it won't happen again. 😛
You are not very clear about the failure. Did it burn up and blow a fuse/breaker? The only power transformer failure I have experienced was a cheap Chinese NiCd charger and it was actually the internal thermal fuse, which I could have replaced. Transformer failure is very, very rare.
Hi all, thanks for all the thoughts. I'll try to answer all the queries. First of all, apologies for the slight lack of details initially: a) I'm not an electronics expert and b) I tend to think people don't like to read long posts!
These are accurate pictures, and it's a toroidal transformer:
Sound more worse after replace cap
On the first monitor that stopped working, the fuse (the external one near the power cable connection) blew, I replaced the fuse, it blew again immediately. I sent it off and the transformer was replaced, and it has worked since. I'm not aware of the specific cause.
On the second monitor that stopped working recently, again the fuse blew, it seemed like the same thing, the only option was to order a new "amp board" (as Adam called it; https://i23.photobucket.com/albums/b383/kwm488/A7/IMG_4078.jpg ) and I installed it myself. Again, I'm not aware of the specific cause.
I will inspect to see if I can install more damping material under the transformer, thanks as_audio
So I just need to work out whether I should order some spare parts in case any of this happens again...
These are accurate pictures, and it's a toroidal transformer:
Sound more worse after replace cap
On the first monitor that stopped working, the fuse (the external one near the power cable connection) blew, I replaced the fuse, it blew again immediately. I sent it off and the transformer was replaced, and it has worked since. I'm not aware of the specific cause.
On the second monitor that stopped working recently, again the fuse blew, it seemed like the same thing, the only option was to order a new "amp board" (as Adam called it; https://i23.photobucket.com/albums/b383/kwm488/A7/IMG_4078.jpg ) and I installed it myself. Again, I'm not aware of the specific cause.
I will inspect to see if I can install more damping material under the transformer, thanks as_audio
So I just need to work out whether I should order some spare parts in case any of this happens again...
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You could measure the voltage of the still working one and choose a good quality higher rated toroid and the tool for crimping the connectors. Problem is the limited space obviously so that is where the challenge lies probably.
The toroid looks very small (and it looks cheap Dong Hua) for a device with 2 x 50W output power. Those active monitors don't live too long apparently as I see them often broken.
No space? Then you can mount the higher rated toroid at the other side. Yes the outside. No heat issues, no space issues. Two holes would be needed to be drilled then for the cables and I would use rubber grommets and silicon caulk to seal the cables.
The toroid looks very small (and it looks cheap Dong Hua) for a device with 2 x 50W output power. Those active monitors don't live too long apparently as I see them often broken.
No space? Then you can mount the higher rated toroid at the other side. Yes the outside. No heat issues, no space issues. Two holes would be needed to be drilled then for the cables and I would use rubber grommets and silicon caulk to seal the cables.
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JP, reason for this "burnout" was already described in post 4,
the toroidal transformer is "big enough" for a small active
speaker like this, the only reason for failure is the use of whimpy,
tiny, or however any big bs electronic multiple advanced knowledge
master would call it - too thin rubber mounting material.
It is as simple as this, sorry.
the toroidal transformer is "big enough" for a small active
speaker like this, the only reason for failure is the use of whimpy,
tiny, or however any big bs electronic multiple advanced knowledge
master would call it - too thin rubber mounting material.
It is as simple as this, sorry.
In many many years of servicing/repairing/restoring solid-state amplifiers, integrated amps, and power amps I have encountered only two failures of toroidal power transformers:
1) A Carver TFM series power amp (I need to look up the exact model) which randomly would blow its AC main fuse. There were no faults on the PC board. Fuse replacement fixed it. But then it blew another AC mains fuse several months later. Again there were no faults on the PC board. However the toroidal transformer itself developed a permanent dead short at this time. This was confirmed by testing the transformer with all windings disconnected. I was unable to identify which winding shorted. I believe it had a dual primary (120/240 selectable) and several secondaries (Carver uses several different rail voltages for the output stage). There were no short circuits between any of the individual windings. The transformer showed no signs of overheating, and no signs of any physical damage. I think I still have this amplifier, but haven’t put it on the workbench in 10 years. I have always wanted to locate the internal short but have plenty of other projects so it went on a back shelf. This transformer has its windings wrapped with plastic tape. The only epoxy is in the “donut hole” of the toroid where the large fastening bolt goes through the middle. I think this transformer weighs 2 or 3 kg.
2) A Japanese power amp (Yamaha?) with a “potted” toroidal power transformer inside a steel can. Potted with epoxy. The thermal cutout opened. But since that thermal cutout is buried deep inside a kilo of epoxy there is no possible way to replace it. That said, this transformer did have a separate pair of leads for the thermal cutout itself. The actual windings, both primary & secondary, were still good. At the time of failure the amplifier was still in-warranty so it got fixed by replacing the transformer.
Among amplifiers with standard E-I laminated cores and bobbin windings I encountered numerous open thermal cutouts (100’s perhaps) but don’t recall any internally shorted or damaged windings. With bobbin windings it is sometimes possible to pull out the failed thermal cutout and insert a new thermal cutout. However, for the case of “in-warranty” repairs the transformer was always replaced. That’s the proper procedure.
-EB
1) A Carver TFM series power amp (I need to look up the exact model) which randomly would blow its AC main fuse. There were no faults on the PC board. Fuse replacement fixed it. But then it blew another AC mains fuse several months later. Again there were no faults on the PC board. However the toroidal transformer itself developed a permanent dead short at this time. This was confirmed by testing the transformer with all windings disconnected. I was unable to identify which winding shorted. I believe it had a dual primary (120/240 selectable) and several secondaries (Carver uses several different rail voltages for the output stage). There were no short circuits between any of the individual windings. The transformer showed no signs of overheating, and no signs of any physical damage. I think I still have this amplifier, but haven’t put it on the workbench in 10 years. I have always wanted to locate the internal short but have plenty of other projects so it went on a back shelf. This transformer has its windings wrapped with plastic tape. The only epoxy is in the “donut hole” of the toroid where the large fastening bolt goes through the middle. I think this transformer weighs 2 or 3 kg.
2) A Japanese power amp (Yamaha?) with a “potted” toroidal power transformer inside a steel can. Potted with epoxy. The thermal cutout opened. But since that thermal cutout is buried deep inside a kilo of epoxy there is no possible way to replace it. That said, this transformer did have a separate pair of leads for the thermal cutout itself. The actual windings, both primary & secondary, were still good. At the time of failure the amplifier was still in-warranty so it got fixed by replacing the transformer.
Among amplifiers with standard E-I laminated cores and bobbin windings I encountered numerous open thermal cutouts (100’s perhaps) but don’t recall any internally shorted or damaged windings. With bobbin windings it is sometimes possible to pull out the failed thermal cutout and insert a new thermal cutout. However, for the case of “in-warranty” repairs the transformer was always replaced. That’s the proper procedure.
-EB
It *is* possible to damage a toroid by improper mounting, possibly shorting adjacent turns together - but that’s mechanical damage not “burnout”.
I agree. I have seen transformers over 100 years old which are still fully functional. Also electric motors.
Magnetic components were pretty much perfected by 1920-1930. At least for transformers and motors which operate on 50/60 Hz AC mains voltage. Other types of components, such as capacitors, had far shorter life expectancies.
-EB
RE: Toroidal power transformers which develop internal shorts:
Could this primarily be a mechanical failure?
Toroid: Magnetic core in the middle. Windings on the outside.
Often mounted between two discs which may be a rather hard material.
Shock and vibration could put enough pressure on the windings to deform the thin enamel/plastic insulation coating on the copper windings. One shorted turn will prevent the transformer from functioning properly.
Toroids should definitely have rubber discs or some sort of flexible material between the clamping discs and the windings. Also the fixing bolt must not be over tightened.
-EB
Could this primarily be a mechanical failure?
Toroid: Magnetic core in the middle. Windings on the outside.
Often mounted between two discs which may be a rather hard material.
Shock and vibration could put enough pressure on the windings to deform the thin enamel/plastic insulation coating on the copper windings. One shorted turn will prevent the transformer from functioning properly.
Toroids should definitely have rubber discs or some sort of flexible material between the clamping discs and the windings. Also the fixing bolt must not be over tightened.
-EB
Re post 32, 33 and 35, building a toroidal transformer you can not (always)
avoid that windings cross each other. These points are the most vulnerable
as far as mechanical mounting is concerned. Most of the time the metal disk
which is used for standard mounting is smaller in diameter than the xformer
itself and rubber material is too weak as seen frequently. Strong mechanical
pressure on the outside layers can damage wire insulation below this disk in
the long term. This could be called a mechanical issue as in post 33, but will
lead to overheating and burnout if fuse protection fails.
avoid that windings cross each other. These points are the most vulnerable
as far as mechanical mounting is concerned. Most of the time the metal disk
which is used for standard mounting is smaller in diameter than the xformer
itself and rubber material is too weak as seen frequently. Strong mechanical
pressure on the outside layers can damage wire insulation below this disk in
the long term. This could be called a mechanical issue as in post 33, but will
lead to overheating and burnout if fuse protection fails.
Still very specific for this device then. Standard quality toroids survive mounting without rubber ring. It is not good to do but I have seen it. I don't like your approach. The question in post #1 was generic and broad so members try to solve the riddle with known knowledge and try to narrow it down like many techs do when trouble shooting. In fact it is the standard way of dealing with errors.
It turned out to be a specific error on a specific device and you knew/recognized the error as it had already been narrowed down/solved/explained in the past. You could have answered straight away when you know this device so good:
"The Adam A7 suffers from a too thin rubber ring under the toroid. I recommend replacing the defective transformer and to put a thicker rubber ring under the new one". Bam! Solved.
PS you accuse me of saying "the plain B word" (ha ha I still have fun 🙂); but now start to become personal "any big bs electronic multiple advanced knowledge master". Which of the 2 is worse in your opinion? I don't care and encourage to be creative in name calling. Challenge!
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There’s a damn good reason for rubber at both sides , AND for just enough pressure to stop it moving as I mentioned in my post3
You risk creating a shorted turn(s), it doesn’t need bolting up with anything more than “just enough” to stop it rotating/moving.
You’ve got even more chance of damage without rubber washers.
I actually replaced a toroid only a couple of weeks ago in a modern (not inexpensive) brand which will remain nameless, where the two (120v) primary’s had a ~20ohms between them!
In that particular case I think it’s both just rubbish QC on the TX manufacturers side AND it was clamped too damn tight !
This finished product brand has form for having dodgy toroids (not particularly high VA - for CD players and DACs mostly) - in my experience. , but this particular one was a month over 2 years old.
You risk creating a shorted turn(s), it doesn’t need bolting up with anything more than “just enough” to stop it rotating/moving.
You’ve got even more chance of damage without rubber washers.
I actually replaced a toroid only a couple of weeks ago in a modern (not inexpensive) brand which will remain nameless, where the two (120v) primary’s had a ~20ohms between them!
In that particular case I think it’s both just rubbish QC on the TX manufacturers side AND it was clamped too damn tight !
This finished product brand has form for having dodgy toroids (not particularly high VA - for CD players and DACs mostly) - in my experience. , but this particular one was a month over 2 years old.
Ok, NOW there is some meat inside this sandwich 😛
I don´t see it as "small" (would need to know diameter+height and/or weight to estimate VA) but reasonable for a supposedly "clean" 2 x 50W amp where only woofer would actually use its available power, don´t see tweeter doing that.
Looks like having about 4" diameter, maybe 2.5" high, nice size.
But in any case I am not certain transformer was damaged!!!
Neither the first nor the second one, go figure.
Why?
In fact it was never diagnosed as such, often *users* ask "it is the transformer, isn´t it?" , I guess because it´s a large mean heavy part they can recognize. 🙂
All we know is:
All customer knows for sure is it was dead and now came back working, which is fine.
This seems to confirm my guess (which is statistically backed):
That said, MAYBE the transformer was physically damaged after all, why not? simply do not see such damage as very common (that´s the understatement of the year).
For some actual numbers, I manufacture Guitar amps, which are routinely abused and moved all over the place by definition.
In over 14.000 amps along over 50 years I have replaced 3 or 4 burnt transformers, and those attributable to users replacing fuses with rolled up aluminum paper or 20 amp fuses pulled from a car, and leaving amp ON even when it starts to smoke.
Not kidding.
A few amps came back with toasted bobbin paper wrapping (you see the browned up band in the middle) or parly molten plastic bobbins .... transformer stinking but still working 😱
I´m certain it helps I use heavy duty MOTOR rated Class F or H wire to wind them, as well as motor rotor or stator rated impregnating varnish, designed to stand high G rotation, vibration and temperature.
Cheap insurance compared to the problem of replacement, shipping heavy stuff far away, etc.
So there is record of too thin poor quality rubber washers beig used, PLUS overtightening by Schwarzenegger arms operators PLUS lack of quality control?
Wow.
Maybe ordering a couple thickish rubber disks would helppeace of mind, on the other hand the lessmessing up with things the worse.
Visually inspect them: if they are, say, 2 or mm thick, they should be fine; if thin as a party balloon .... by all means replace them.
They might stop carrying replacements in the future.
Personally I wouldn´t overthink it, just use and enjoy them.
In a nutshell, and back to the original post, and just for the sake of completeness:
Transformers are wonderful machines, no moving parts **NO WEAR** , over 95% efficient (if properly designed).
IF you have spare money and it gives you peace of mind, fine.
Of course next time it might actually be a transformer, a dead speaker, whatever.
Or they overheat badly, smoke, stink of toasted varnish, you replace them quickly for fear of them catching fire and burning your home.
Interesting.Hi all, thanks for all the thoughts. I'll try to answer all the queries. First of all, apologies for the slight lack of details initially: a) I'm not an electronics expert and b) I tend to think people don't like to read long posts!
These are accurate pictures, and it's a toroidal transformer:
I don´t see it as "small" (would need to know diameter+height and/or weight to estimate VA) but reasonable for a supposedly "clean" 2 x 50W amp where only woofer would actually use its available power, don´t see tweeter doing that.
Looks like having about 4" diameter, maybe 2.5" high, nice size.
But in any case I am not certain transformer was damaged!!!
Neither the first nor the second one, go figure.
Why?
Statistics point 99% to blown power amp (TDA7294) and 1% (or less) to transformer, specially on a Studio Monitor which does not travel around or get bumped but sits comfortably in a Studio.
In fact it was never diagnosed as such, often *users* ask "it is the transformer, isn´t it?" , I guess because it´s a large mean heavy part they can recognize. 🙂
All we know is:
A dead power board might have been replaced, or even repaired at component level.
All customer knows for sure is it was dead and now came back working, which is fine.
This seems to confirm my guess (which is statistically backed):
and now we are certain of what was actually done, because:
Also:
which of course is fine from an end user point of view, all he wants is his unit back to normal, period.
That said, MAYBE the transformer was physically damaged after all, why not? simply do not see such damage as very common (that´s the understatement of the year).
For some actual numbers, I manufacture Guitar amps, which are routinely abused and moved all over the place by definition.
In over 14.000 amps along over 50 years I have replaced 3 or 4 burnt transformers, and those attributable to users replacing fuses with rolled up aluminum paper or 20 amp fuses pulled from a car, and leaving amp ON even when it starts to smoke.
Not kidding.
A few amps came back with toasted bobbin paper wrapping (you see the browned up band in the middle) or parly molten plastic bobbins .... transformer stinking but still working 😱
I´m certain it helps I use heavy duty MOTOR rated Class F or H wire to wind them, as well as motor rotor or stator rated impregnating varnish, designed to stand high G rotation, vibration and temperature.
Cheap insurance compared to the problem of replacement, shipping heavy stuff far away, etc.
So there is record of too thin poor quality rubber washers beig used, PLUS overtightening by Schwarzenegger arms operators PLUS lack of quality control?
Wow.
Maybe ordering a couple thickish rubber disks would helppeace of mind, on the other hand the lessmessing up with things the worse.
Visually inspect them: if they are, say, 2 or mm thick, they should be fine; if thin as a party balloon .... by all means replace them.
I think, based on your two examples, that what may happen again is blown Electronics ..... if you have or can get a spare board, why not?
They might stop carrying replacements in the future.
Personally I wouldn´t overthink it, just use and enjoy them.
In a nutshell, and back to the original post, and just for the sake of completeness:
"Should?": never.
Transformers are wonderful machines, no moving parts **NO WEAR** , over 95% efficient (if properly designed).
You didn´t 😀; you sent full monitor dead and it came back working; many users assume "it´s the tranformer", usually not really but why argue? they just sent you a working unit and that´s all that matters.
Again suspect an electronics problem , but your full replacement (which now you did, not the Factory) covers all angles, not specifically confirmig or denying any of them.
Flip a coin, no ample statistical data to back yes or no.
IF you have spare money and it gives you peace of mind, fine.
Of course next time it might actually be a transformer, a dead speaker, whatever.
Doubt it was the actual problem, and a "bad batch" would have dozens of examples all over the Net or would fail much sooner than 5 years or both ... I don´t see that happening.
Not, not reasonable at all, transformers do not wear, they either stand the load or burn quickly.
Or they overheat badly, smoke, stink of toasted varnish, you replace them quickly for fear of them catching fire and burning your home.
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Not a single word French 🙂
Now there are old transformers that have their windings connected to wire studs/lugs or whatever they are called. Perfect! There are also transformers that have lead wires with colored isolation sleeves. The plastic isolation of those wires sometimes does deteriorate. With recent transformers made in a certain country I notice PVC to be instabile and becoming brittle. Transformers therefor don't have a perpetual life but the old ones made of non recycled materials can have a very long useful life.
Now there are old transformers that have their windings connected to wire studs/lugs or whatever they are called. Perfect! There are also transformers that have lead wires with colored isolation sleeves. The plastic isolation of those wires sometimes does deteriorate. With recent transformers made in a certain country I notice PVC to be instabile and becoming brittle. Transformers therefor don't have a perpetual life but the old ones made of non recycled materials can have a very long useful life.
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If you have a transformer failing from shock and vibe, just use a thick FOAM pad on top and bottom, not the rubber disc that comes with it from the factory. Either that or properly varnish-impregnate it first (which is a pain to do properly, and makes things worse if it never dries out). Potted centers are a big help, because you can use a thick foam pad at the bottom and still get airflow over the windings on top. If you can’t get a factory original, you might be able to get something off the shelf that’s close enough.