NO. This is an “X2” capacitor which is mains rated, that is it can handle the mains power at 240VAC. Capacitance 1.0knF or 1µF @ 275VAC. The X2 is a type designator and signifies mains use.
See not quite enough information first time around.
That also tells me that the 500V caps are electrolytic and they probably were operated at 300V+
True that WOULD give you a nasty sting if you happen to find one charged up. The secondary effect like colliding with a sharp object when you get the “bite” would most likely cause some damage.
The 2 heavy inductors along with the X2 caps would be part of a mains filter. The light blue discs are probably varactors as part of the filter.
390µF @ 500V electrolytics would indicate a high voltage (300V +) DC power supply for this machine so make sure any mains lead is unplugged before fiddling…
It would be common practice to have some sort of bleed resistor across each of these caps so if it has been unpowered for some time it should be safe. Would not hurt to check for any residual voltage though just to settle your mind. You can do this quite OK with a DMM.
A 5V plug pack does this too but doesn’t produce 500V.
Cheers Bob
They will almost certainly be smoothing capacitors following a full bridge rectifier, so they were run at ~350V (240x1.4). Usually they will have a discharge resistor across them - look for a high value high wattage resistor across the capacitor. Even if it’s not there the voltage will have dissipated if they haven’t been run in a while. Get a well-insulated screwdriver and just touch it across the terminals - there might be a bit of a crack and a small spark, but it’s nothing to be concerned about if you are well insulated through the screwdriver handle and you are expecting it.
It’s not between you and 500V. It’s 500V between the terminals - nothing to do with you unless you touch a terminal. That screwdriver looks fine. To be super-cautious you could be sure you are not touching the frame while shorting the terminals, in case one terminal is at frame potential.
That screwdriver is much safer than multimeter probes. With the probes the current flows through the cable (across the back of your hand??, over the frame??) through the multimeter and back. With the screwdriver it flows across a centimeter of heavy steel. It is a good habit to get into to discharge any capacitors that are part of a power supply as a matter of course whenever you open a case, even a 5V wall wart because some of them do have capacitors across the supply and sometimes they don’t bother with discharge resistors because there isn’t the room.
I wouldn’t say that although both are OK in this instance. I would suggest the modern day DMM probe would be equally as good as the screwdriver. The surface area of the insulating material between the business end and your fingers has a lot to do with the actual breakdown point.
Good advice. Reminds me of my working days.
One project was the installation and commissioning of 40kW HF transmitters. These had quite a power supply. The PA was valves in a grounded screen configuration. -1200V on the cathode with a further -300V supply sitting on that for grid bias (adjustable). The anodes had about +6500V volts and the whole thing would supply some 10.5A without upsetting any overloads. The filter caps were I think 16µF 10kV oil filled paper types. They had bleed resistors across them but still took some appreciable time to discharge. There were mechanical interlocks on the access doors arranged so that when any door was opened a great big shorting bar came down across the caps and discharged them in a big hurry.
You can imagine the size of the spark if you switched the unit off then opened the door too soon. BANG!!! Big time.
Cheers Bob
Could anyone who owns this multimeter let me know how well it works, if you have had any troubles with it, how long you have owned it, or anything else relevant?
I’d like to buy one but there is a review that says:
“When i switch to resistance to measure the resistance, display shows 0L or over range. It doesn’t show anything else after that. is this a problem with the tool or i am doing something wrong?”
I’m looking to use it for measuring DCV and resistance, so this review describing an issue is worrying.
If you are questioning the bit about the DMM displaying “OL” (Over Load or over range) on the resistance range it leads me to believe you are pretty much unfamiliar with this type of instrument. This is completely normal and it means the DMM is trying to measure a resistance beyond its maximum capability. The leads are at this stage not touching so are completely open circuit so thus an extremely high resistance (air).
So do not let this little gem deter you as there is nothing wrong with this scenario. But I would suggest you do a little reading on this type of device and take note of the Pros and Cons (not many Cons) and don’t be frightened by the specification sheet. It all means something but at first it probably won’t mean anything to you. But don’t throw it away. It will all gradually make sense over time and can be of use if something does not seem just right.
I note that Core actually publish the data sheet. Just had a quick look and looks pretty normal so if the build quality is up to scratch this would be pretty good value at about $54 for what would be better than “entry level” instrument.
I stress here that my comments are “sight unseen” as I have not had any experience with this particular instrument. But it does all the things that a modern DMM usually does and the data sheet would indicate it is just as good as most. So if you need one I suggest that for the price buy it. These things can cost many hundreds (even $k) and would be full of features you would never use.
Have a look at the Data sheet first and if you can understand it then decide.
One comment. Like all instruments of this type I would not take a lot of notice of the claim for up to 9.999MHz frequency range. Even the meter leads could upset a circuit operating at this sort of frequency but this is of little consequence as long as you are aware. The highest frequency you would be interested in measuring would be in the hundreds of Hz or a few kHz. Like don’t expect to measure the clock frequency of an Arduino or something like that.
Cheers Bob
Yeah, this will be my first multimeter. I did do a bit of research about the meaning of specifications in the datasheet (which I’m glad Core provides) and came to this as my best option for the price. Thanks for clarifying the weird review. I’ll be getting it now!
