Hi
I would like to know how you test your power supplys, amplifiers,... to see if they work properly. Problem is when you have a lot of power, few 100 watts, on/with what you test that level of power and maybe for how long.
I mean if supply/amp can work at its power for 10min, there is no reason that it wouldn't work for 1h, 10h, days... is there?
I will show my power load that I'm making now in few days.
I would like to know how you test your power supplys, amplifiers,... to see if they work properly. Problem is when you have a lot of power, few 100 watts, on/with what you test that level of power and maybe for how long.
I mean if supply/amp can work at its power for 10min, there is no reason that it wouldn't work for 1h, 10h, days... is there?
I will show my power load that I'm making now in few days.
Just slab together cheapest power resistors you can find.luka said:
For short-time testing water cooling can be very helpfull, single 4w resistor can handle more than 20x normal power rating submerged in water.
And I was trying to figure out how to make easily cheap and small 0.01ohm dummy load rated for 50kW
🙂
Hi mzzj,
Try using heaters.
Hi luka,
Consumer amplifiers will not deliver their full power for very long. If you manage to keep the heat sinks and amplifier components cool, the thermal fuse in the transformer core will open. Scratch one power transformer. Don't test them any longer than you have to.
I use proper Dale low inductance 8 ohm, 250 watt dummy loads mounted on heat sinks (with grease) that I had resurfaced in a machine shop. The surfacing cost as much as the resistor back then. One of my guys still blew a resistor up testing a Yamaha pro amp (P-2200 I think). He had it bridged and it blew one end out of the resistor.
When I test a consumer amplifier at full power, it's only on long enough for the reading to settle, about 30 sec. Running an amp at 1/3 power will overheat it as well. So if you want to do an extended power test you must check your temperatures with a proper thermocouple temp gauge. Make sure you check the heat sinks and the transformer core. It will not hurt to check a few free standing transistors in the driver stage.
Do not forget that a transformer core builds heat slowly. It holds it for a long time also. I have seen guys wipe out transformers on the bench (thank goodness they weren't my guys!).
-Chris
Try using heaters.
Hi luka,
Consumer amplifiers will not deliver their full power for very long. If you manage to keep the heat sinks and amplifier components cool, the thermal fuse in the transformer core will open. Scratch one power transformer. Don't test them any longer than you have to.
I use proper Dale low inductance 8 ohm, 250 watt dummy loads mounted on heat sinks (with grease) that I had resurfaced in a machine shop. The surfacing cost as much as the resistor back then. One of my guys still blew a resistor up testing a Yamaha pro amp (P-2200 I think). He had it bridged and it blew one end out of the resistor.
When I test a consumer amplifier at full power, it's only on long enough for the reading to settle, about 30 sec. Running an amp at 1/3 power will overheat it as well. So if you want to do an extended power test you must check your temperatures with a proper thermocouple temp gauge. Make sure you check the heat sinks and the transformer core. It will not hurt to check a few free standing transistors in the driver stage.
Do not forget that a transformer core builds heat slowly. It holds it for a long time also. I have seen guys wipe out transformers on the bench (thank goodness they weren't my guys!).
-Chris
First of all I am doing electronics only for me, so things are rated as they are, not dependent on time, I like that for myself. I don't like big transformers anymore or linear amps, I'm all into switching... so there is almost no heat 😉
Hi mzzj
I was thinking about resistors at first. But one 5w resistor costs 0.38€ here and you need a lot of them, and then you have your power resistor rated at what 400w? And you have to use water, which is on same desk as rectified 230Vac
and I don't wan't water to boil and worry about that 
Hi Chris
I agree, heaters are the way to go. But I don't feel like buying one big, having only one resistance.... I used heaters from baking oven (some microwave have them too). Each has about 66 ohmes and is rated at 800w free air. Now I have 5 of those. And I will put them in tunnel with 120mm/230Vac fan pushing about 300m^3 per hour. So rating of each should go up a lot, but still won't be so hot that you couldn't have it in room, on desk...
And I have spend less then 2€ by now, to buy two 30cm ALU-profiles and M4 1m long screw
Hi gmphadte
Yea, but you would produce a lot of chloride, if you test with DC, but sure would be a way. But resistance would be unknown and changing...
Hi mzzj
I was thinking about resistors at first. But one 5w resistor costs 0.38€ here and you need a lot of them, and then you have your power resistor rated at what 400w? And you have to use water, which is on same desk as rectified 230Vac
and I don't wan't water to boil and worry about that Hi Chris
I agree, heaters are the way to go. But I don't feel like buying one big, having only one resistance.... I used heaters from baking oven (some microwave have them too). Each has about 66 ohmes and is rated at 800w free air. Now I have 5 of those. And I will put them in tunnel with 120mm/230Vac fan pushing about 300m^3 per hour. So rating of each should go up a lot, but still won't be so hot that you couldn't have it in room, on desk...
And I have spend less then 2€ by now, to buy two 30cm ALU-profiles and M4 1m long screw
Hi gmphadte
Yea, but you would produce a lot of chloride, if you test with DC, but sure would be a way. But resistance would be unknown and changing...
I think that the amateur radio people often submerge a resistor in a one-gallon "paint can" full of some kind of oil, to use as a high-power dummy load in place of their transmitting antenna. There was even a commercial product for that, called something like can-tenna.
- Tom Gootee
http://www.fullnet.com/~tomg/index.html
- Tom Gootee
http://www.fullnet.com/~tomg/index.html
Hi Tom,
Hi luka,
-Chris
Yes. It works well (the concept). Make sure you seal the can so you don't get a messy surprise.
Hi luka,
That's cool. So it depends on how close you want to be to standard accepted practices.
Look for dead toasters. There ought to be many for free. I have no idea what the element resistance is. They even come premounted.
Yes, the rating will go up and it would be safe to use. For reduced fan noise, place the fan in the center of the tube and run it slower than designed for.
Yeah, I didn't comment. 😀
-Chris
An externally hosted image should be here but it was not working when we last tested it.
this is what I use. 15x 10w 56 ohm resistors parallel each side.
I figured if the amp would survive bench testing on 3.7ohm loads then it will do 4ohm easy. besides, resistance goes up when they start heating up. 🙂
Cantenna can use clean engine oil. Mineral oil is better, like baby oil.
Sealing it is actually a very bad idea, it gets hot in use and the lid pops off and makes a mess. I found out the hard way....
A small (1 litre) Cantenna is better, It is much more portable and if you need more power you put it in a bucket, the sink or even the bath.
I suggest soldering a thread onto the top of the can with a removable cap to allow it to breathe when in use.
For big AC power supplies & UPS I use a 10 amp variac with an electric kettle.
For a fixed current load for discharge testing 24V battery packs I made a 7810 voltage regulator feeding a 10 ohm resistor.
Sealing it is actually a very bad idea, it gets hot in use and the lid pops off and makes a mess. I found out the hard way....
A small (1 litre) Cantenna is better, It is much more portable and if you need more power you put it in a bucket, the sink or even the bath.
I suggest soldering a thread onto the top of the can with a removable cap to allow it to breathe when in use.
For big AC power supplies & UPS I use a 10 amp variac with an electric kettle.
For a fixed current load for discharge testing 24V battery packs I made a 7810 voltage regulator feeding a 10 ohm resistor.
Hi Mike,
-Chris
For sure. Just make sure it is sealed when not in use. You haven't lived until you have to clean this mess up from your electronics bench.
-Chris
Hi
You see. That why I don't wan't anything liquid on my bench, like water or oil
Power resistors with forced air seems at this point to be better choise...
You see. That why I don't wan't anything liquid on my bench, like water or oil
Power resistors with forced air seems at this point to be better choise...
Hi zeonrider
Have you run your power resistor at some higher power level for any longer period of time, so that it did heat up a lot? I am thinking of using same lab sockets, which are rated around 80-100 degrees. I worrie what if air inside generated by resisotors will be 300, then over time case will heat up to that temp. too, melting plastic. Did you have anything like that in your case, or it doesn't heat up that much?
And what is that red thing around sockets?
Have you run your power resistor at some higher power level for any longer period of time, so that it did heat up a lot? I am thinking of using same lab sockets, which are rated around 80-100 degrees. I worrie what if air inside generated by resisotors will be 300, then over time case will heat up to that temp. too, melting plastic. Did you have anything like that in your case, or it doesn't heat up that much?
And what is that red thing around sockets?
gmphadte said:
Indeed, if you have use for the chlorine that gasses out. Your lungs and most anything organic around you (the dreaded "enviroment") don't.
X-rays were used to fit shoes once.juergenk said:
Asbestos was used in brake discs once.
Mercury was used to "cure" syphilis once.
... and Chlorine was used to kill enemy troops once.
massdevelopment of chlorine is limited to DC, in case the saltwater is used as AC-load only, there may be small amounts of chlorine escaping the water
if this leads to a dangerous level in a well vented enviroment, is at question.
I suppose saltwater is a bad dummy load for amplifiers, because of the large! tempco, the frequency behaviour and whatever.
regards
if this leads to a dangerous level in a well vented enviroment, is at question.
I suppose saltwater is a bad dummy load for amplifiers, because of the large! tempco, the frequency behaviour and whatever.
regards
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