I finished my Zen V2 today, sounds pretty good !!
But I have a problem: My transformer gets hot, I think about 45 to 50 degree Centigrade (I can put my fingers on it, doesn't really hurt, but it's hot).
Since I have no information about the transformer I'am wondering if it is too small.
Can anybody give me a hint ?
Thanks in advance Till
But I have a problem: My transformer gets hot, I think about 45 to 50 degree Centigrade (I can put my fingers on it, doesn't really hurt, but it's hot).
Since I have no information about the transformer I'am wondering if it is too small.
Can anybody give me a hint ?
Thanks in advance Till
I would say that if your transformer is getting that warm you will start to encounter two problems. Regulation will increase with temp as the resistance in the wire increases.I would guess that beyond a certain point this will run away with itself and produce a meltdown. The effect of increased regulation is reduced power output as the line voltage drops.
Significant amounts of heat will stress the transformer wires enamel and eventually the transformer will short circuit.
The only advantage I experienced with my Zen V3 and a hot running transformer is that it acts as a power supply choke, which gives a nice warm sound to the amp and reduces hum.
The heat is also likely to shorten the life of your valuable filtering capacitors, which is a real problem.
Unfortunately I would say that you need to replace your transformer with something much beefier, I would only really be happy if my transformer were running at ambient temps. To do otherwise might be an expensive mistake.
Shoog
Significant amounts of heat will stress the transformer wires enamel and eventually the transformer will short circuit.
The only advantage I experienced with my Zen V3 and a hot running transformer is that it acts as a power supply choke, which gives a nice warm sound to the amp and reduces hum.
The heat is also likely to shorten the life of your valuable filtering capacitors, which is a real problem.
Unfortunately I would say that you need to replace your transformer with something much beefier, I would only really be happy if my transformer were running at ambient temps. To do otherwise might be an expensive mistake.
Shoog
Just to say I agree with the sensible replies here.
A class A amplifier transformer is going to run hot, by definition.
50C is not hot for an operating temperature, by 65C which
is too hot to touch then things are becoming marginal.
Thermal cutouts fitted in transformers operate at at about
100C to 110C internal temperature of the transformer.
Offload and onload power supply voltages will tell you if the
transformer is too small.
sreten.
A class A amplifier transformer is going to run hot, by definition.
50C is not hot for an operating temperature, by 65C which
is too hot to touch then things are becoming marginal.
Thermal cutouts fitted in transformers operate at at about
100C to 110C internal temperature of the transformer.
Offload and onload power supply voltages will tell you if the
transformer is too small.
sreten.
First thing in the morning, with the transformer cold and at a *known* temperature, measure the resistance of the primary. Then set the amp going for several hours, then unplug it and straight away measure the resistance again. There are formulas around for calculating the temperature rise of copper based on it's known increase of resistance with temperature. If you can't find one, post the cold and hot resistance values and the cold temp of the tranny and someone here will work it out.
Now I'm able to answer my own question ;-)
From my measurement the primary reaches (after about 3 hours) a steady state temperature of approximately 70C (soft) to 80C (loud). So there should be no problem, at least in winter.
I have to think a bit, how it will behave with higher room temperature.
Thanks for your help Till
From my measurement the primary reaches (after about 3 hours) a steady state temperature of approximately 70C (soft) to 80C (loud). So there should be no problem, at least in winter.
I have to think a bit, how it will behave with higher room temperature.
Thanks for your help Till
I still think your pushing it, and unless your caps are mounted well away from the transformer, you might be shortening their lives considerably. The caps in a Zen cost lots of money.
I also think that each time the transformer heats and cools it will be putting the enamel under mechanical stress through expansion and contraction.
I also found that when I was testing my Zen, out in the open with plenty of air circulating, things were relatively fine. When I moved it into its intended resting place, which was a bit more restricted, with poorer air flow, things started to get much hotter.
If you definately intend to use that transformer, I would say the fan sujestion would be a very good idea. If you use a computer case fan, and run it at half voltage they are said to be silent enough.
Still that still just my gut feeling.
Shoog
I also think that each time the transformer heats and cools it will be putting the enamel under mechanical stress through expansion and contraction.
I also found that when I was testing my Zen, out in the open with plenty of air circulating, things were relatively fine. When I moved it into its intended resting place, which was a bit more restricted, with poorer air flow, things started to get much hotter.
If you definately intend to use that transformer, I would say the fan sujestion would be a very good idea. If you use a computer case fan, and run it at half voltage they are said to be silent enough.
Still that still just my gut feeling.
Shoog
@shoog:
You are right. I should have written to my last posting, that I probably will answer my question with: It's too hot ;-)
Without doing a detailed calculation I think that with higher room temperature (in summer, maybe 35C) and mounted in an enclosure the temperature could rise well over 100C so I will have to by a new transformer (probably two), sniff :-(
Greetings and a happy new year Till
You are right. I should have written to my last posting, that I probably will answer my question with: It's too hot ;-)
Without doing a detailed calculation I think that with higher room temperature (in summer, maybe 35C) and mounted in an enclosure the temperature could rise well over 100C so I will have to by a new transformer (probably two), sniff :-(
Greetings and a happy new year Till
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Shoog said:
I know for a fact that this statement is wrong....well it may be true, but the effect is going to take a few centuries to actually damage the coating of the wire.
Eric said:
40C over ambient is realistic, and a maximum temperature at 105C.
A 1000VA trafo will rise to 72C over ambient at full load.
So you can use your trafo with full confidence in it, anything else would be a waste of a correctly dimentioned trafo
Actually your trafo is overkill if its running at 50C
Magura
This is supposed to be the fearless world of diy. We're not worried about a 5% failure ratio here. That only means replacing a part or two in one of 20 amps. It might be a bit more of a problem for Pioneer to replace 5% of the low rent AV receivers it produces, but not here. If you have the part, run it until it melts. If it melts and lets the majic smoke out, replace it with a bigger one.
No balls, no blue chips
I did read about increased heat after the case is all closed up. I've noticed a lot of amps made here without adequate internal ventalation. And all joking aside, if your closed amp runs 70 deg c inside, you are greatly reducing the life of your expensive psu caps. And after you've exausted your supply of surplus caps, you could be buying new ones to avoid reworking the hole mess at a much higher price.
No balls, no blue chips
I did read about increased heat after the case is all closed up. I've noticed a lot of amps made here without adequate internal ventalation. And all joking aside, if your closed amp runs 70 deg c inside, you are greatly reducing the life of your expensive psu caps. And after you've exausted your supply of surplus caps, you could be buying new ones to avoid reworking the hole mess at a much higher price.
My experience of running an EI transformer at about 70 degrees was that I could distinctly smell it, which to my mind shows that something is melting (possably only the wax - but thats not good).
Torodials are built without such stuff as waxed paper so they will probably go much hotter without as much trouble.
Still in the end its what you feel comfortable with, and I certainly don't like my amps running any hotter than they absolutely have to. In the world of Ebay the transformer becomes one of the cheaper components in the amp, so why push it- and shorten the life of you filter caps - which are the most expensive.
Shoog
Torodials are built without such stuff as waxed paper so they will probably go much hotter without as much trouble.
Still in the end its what you feel comfortable with, and I certainly don't like my amps running any hotter than they absolutely have to. In the world of Ebay the transformer becomes one of the cheaper components in the amp, so why push it- and shorten the life of you filter caps - which are the most expensive.
Shoog
Trivia from the power companies
I have ingrained in my head from University (anno 1987) that the big bad (transformer) boys that the power companies use will last pretty much forever if the core temperature does not rise above 97 degC. After that they expect a halving of the life of the equipement for every additional 3 degC rise.
I never got anyone to commit to what a halving of "pretty much forever" was ...
For audio transformers it must be related to the isolation material. Bear in mind that you can easily get hotspots - let's say that you pass too high a current on a cold transformer - the average temperature will be low but the copper temperature will easily pulse way higher.
With transformers I am very careful. If I cannot touch it with bare fingers for a long time - it is way too hot for me. Some audio companies use poorly constructed units - I have seen transformers that are way above this temperature without load ...
Petter
I have ingrained in my head from University (anno 1987) that the big bad (transformer) boys that the power companies use will last pretty much forever if the core temperature does not rise above 97 degC. After that they expect a halving of the life of the equipement for every additional 3 degC rise.
I never got anyone to commit to what a halving of "pretty much forever" was ...
For audio transformers it must be related to the isolation material. Bear in mind that you can easily get hotspots - let's say that you pass too high a current on a cold transformer - the average temperature will be low but the copper temperature will easily pulse way higher.
With transformers I am very careful. If I cannot touch it with bare fingers for a long time - it is way too hot for me. Some audio companies use poorly constructed units - I have seen transformers that are way above this temperature without load ...
Petter
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