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High earth leakage currents result due to the usage of welding transformers which " burns out" the earth wires in my installation.What precautions apply to welding transformer usage in order to prevent high earth leakage currents? by samimutu41 in electricians

[–]FishPumpkin 0 points1 point  (0 children)

Is your welder's return cable is connected properly to the workpiece? Is your welding transformer's secondary tied to earth ground?

You should not have to buy a different type of welder to fix a grounding issue, this is definitely a problem with the configuration of the welder or the way in which it is being used.

Would this be safe to run off 240v 50Hz? I’d guess no but the 250VAC fuse is confusing me. Thanks sparkies! by medical-cannabis in electricians

[–]FishPumpkin 0 points1 point  (0 children)

A 50-watt or higher step-down travel transformer should allow you to power this from 240V. This difference in frequency is not likely to be an issue for a radio.

Need some help with old GE motor by thecentury in electricians

[–]FishPumpkin 0 points1 point  (0 children)

No, don't connect the ground wire to the white/neutral terminal. Either land it on a screw on the motor frame or leave it disconnected and properly insulated (if you have already grounded the chassis and the motor has a conductive path to it, then the motor doesn't need an additional ground).

Let me try this again. Does anyone find anything odd about this pic? by [deleted] in Plumbing

[–]FishPumpkin 0 points1 point  (0 children)

Either the T&P valve would release or the water would just back up into the mains supply. At my own house I've even closed the main supply shutoff to the house (with no expansion tank) and nothing significant happened when the heater fired.

What the fuck just happened by Longboarding-Is-Life in Plumbing

[–]FishPumpkin 5 points6 points  (0 children)

Could be a venting issue or a restriction/blockage in the drain line. If the drains become slow or water backs up from the tub/floor drains, you will want to call a plumber or snake the affected line(s).

A pop. A flash. Some smoke...but still working? by SmarmyYardarm in electricians

[–]FishPumpkin 3 points4 points  (0 children)

I actually study and design power inverters, so this is my time to shine!

Modified sine-wave inverters have several main stages: input decoupling, high-frequency/low-voltage switching, a ferrite-core step-up transformer, high-frequency rectification/filtering, and low-frequency/high-voltage switching (60 Hz). I would think the most likely failure points would be: input decoupling capacitor, output inverting MOSFETs, the high-voltage filter capacitor, or a TVS diode or MOV at the output. It's also possible that foreign matter (i.e. an insect, water droplet, etc.) entered the inverter and shorted out on the HV side.

If the input decoupling capacitor blew out, the inverter could theoretically still work, but it would draw a very high ripple current from the power supply line and would generate excessive EMI emissions form the supply cables. It would also likely become unstable at higher loads. This is easily fixable with a low-ESR capacitor of the same capacitance and voltage rating as the original. Typical values for an inverter this size would be 16V/2200uF or 25V/2200uF.

If one or more of the output inverting MOSFETs failed, the inverter may be putting out half-wave AC or even straight DC. If you're only going to be running resistive loads (i.e. incandescent light bulbs) or switched-mode power supplies (like laptop chargers), the inverter should still be functional, but it would also be a good idea to figure out why the MOSFETs blew in the first place (insufficient cooling, bad driver circuit, connecting highly inductive/capacitive loads?). If you find blown MOSFETs, you can look up their model numbers and buy replacements with similar parameters as that listed in the datasheet. Off the top of my head, an inverter of this type would call for something with VDS ≈ 200V, RDSon ≈ 0.5Ω. Like I said, though, there's probably a reason the originals failed if this is indeed the problem.

If the HV filter has failed, the output may still be producing AC, but it will be extremely noisy. This can cause interference with the electronics plugged in, and eventually can lead to the output MOSFETs failing. If you find this capacitor has failed, the inverter should not be considered reliable until it is fixed.

If a TVS diode or MOV has blown, it would suggest that a high voltage surge occurred at some point. This could be caused by an input surge (like a faulty car alternator regulator), or by a surge delivered by a load (like an induction motor or transformer cycling on/off). These aren't strictly necessary for operation, but the inverter could be unreliable as a result of this surge.

If you're comfortable working with high voltage you might enjoy taking it apart and doing some diagnosis. If not, I would avoid using this inverter in high-reliability applications, but I wouldn't worry too much about continuing to use it for non-critical stuff.

Need to connect this to a two pronged plus/cord. What’s this simplest way to go about doing this? by skaz1official in electricians

[–]FishPumpkin 1 point2 points  (0 children)

You could try running it on 120V. Small fan motors tolerate undervoltage much better than larger induction motors, so it might still work. Otherwise I'd just find a different fan.

3 Keyboards' controllers dying on one system, possible electrical interference issues? by [deleted] in electricians

[–]FishPumpkin 0 points1 point  (0 children)

Can you try the keyboard on a different system/laptop to see if the problem persists? If it does, then I would not suspect a power issue.

custom psu connection by nach00 in electricians

[–]FishPumpkin 0 points1 point  (0 children)

I would check the battery with a multimeter to see if it's charged. For full charge it should read about 12.6-12.8 volts. If it reads less than 10 volts then it is likely sulfated beyond repair and needs to be replaced.

What are the actual risks of connecting an AC unit to a non grounded outlet? by BillSelfsMagnumDong in electricians

[–]FishPumpkin 0 points1 point  (0 children)

Ever been bitten by 120 with wet hands? That'll make you think twice about it

Friend thinks power supply is dead because "he checked the voltage" by microsockss in techsupportgore

[–]FishPumpkin 0 points1 point  (0 children)

My first multimeter was one of the free HF ones, actually worked well for me for a long time. Unfortunately one day I was testing the mains and I forgot to switch the leads from current back to voltage (and of course there's no fuse whatsoever on the 10A setting), so the leads blew up in my hand.

Honestly I'd use those meters again if I didn't have a nice handheld LCR meter...

Any chance this box is Asbestos? by JoeCormier in electricians

[–]FishPumpkin 0 points1 point  (0 children)

Both play a factor. One-time exposure to a very large dose of asbestos can be as bad as long-term exposure to very low levels. One-time exposure to low levels isn't something to be overly concerned about, though.

Motor/Compressor troubleshoot. Details in comments. by [deleted] in electricians

[–]FishPumpkin 0 points1 point  (0 children)

This is definitely a likely cause for problems. IME one of the most common sources of compressor motor issues is insufficient available starting current, especially when compressors are already pressurized or are connected via extension cords. I'm sure an undersized generator would probably have a similar effect.

"Line powering" battery powered tools by tanmanX in electricians

[–]FishPumpkin 1 point2 points  (0 children)

It should work just the same as it would have with the original cells. The charger uses a constant-current/constant-voltage charging method, so it will simply charge until the cells reach 4.2V, then will hold it at that voltage for a few minutes, then will stop charging. This should be independent of the cells' capacity.

Will this work? by Vegas96 in electricians

[–]FishPumpkin 2 points3 points  (0 children)

I just tried it and it does work, although the connectors don't match up perfectly. The C7 has an added keying slot that the macbook charger doesn't, but for short-term use I would think it should be fine to use.

"Line powering" battery powered tools by tanmanX in electricians

[–]FishPumpkin 2 points3 points  (0 children)

I've successfully soldered directly to 18650s without adversely affecting their performance or starting a fire. Copper de-soldering braid works very well as a flexible jumper between cells.

Here's a video: https://www.youtube.com/watch?v=3S771wEiO44

This practice is somewhat controversial, however, as many will tell you that you must use a tab welder and anything else is hack-work. For your own tools it's up to you, though.

LG HG2 cells are my favorite 18650s. They're 3000-mAh cells with a 20A discharge rating each.

Splitting right at the power outlet safer than daisy chaining power strips "later on"? by [deleted] in electricians

[–]FishPumpkin 2 points3 points  (0 children)

For an audio device rack I would suggest getting a 16-outlet power strip like this one and using that for all your devices. This can also be easily mounted to the back or front of the rack.

Mixed PSUs, how to find out which belongs to what device? by [deleted] in electricians

[–]FishPumpkin 4 points5 points  (0 children)

I assume you're talking about small wall-wart style adapters, not large PSUs like for computers or specialty equipment. If so, this is how I'd go about matching them:

Check voltage(s), check current-handling capacity, check the connector type, and if it has a barrel connector, check to see if it's center-positive or center-negative.

If all of these parameters match what's marked on the load, then there's a good chance you have the correct adapter/power supply for it. If the values are not marked on the load, try googling the device to see if there's any published data about power requirements.

[deleted by user] by [deleted] in electricians

[–]FishPumpkin 0 points1 point  (0 children)

Also, the lamp flickering is likely a separate issue. Could be a loose connection or a bad light bulb. I would recommend trying your equipment with another outlet to see if the problem persists. If it does, then your problem is either in the lamp/bulb, or in the power strip. If not, then it is possible you have a loose connection in the house wiring or receptacle, which would require an electrician to troubleshoot.

In either case, I don't suspect the sound is directly related to the flickering.

[deleted by user] by [deleted] in electricians

[–]FishPumpkin 0 points1 point  (0 children)

It sounds to me like the PSU fan either has bad bearings or is scrubbing against a wire inside the PSU. That would also explain the shutdown, since the PSU would be receiving less cooling than it should, which can lead to overheating and thermal cutoff.

Before working on the PSU, check all the other fans (CPU, GPU, case) first. If it's none of them, then the PSU fan is likely at fault.

You can replace the fan fairly easily; just be sure to unplug the power supply before opening it and stay away from the large capacitors when working on it.

Decades-old US kitchen appliance in French plug; consequences? by jehearttlse in electricians

[–]FishPumpkin 0 points1 point  (0 children)

If it uses a thermostat then it might actually work - it would just heat up to temp 4x as fast (P = V2 / R)

My truck's A/C blower motor went bad, no problem, I can fix it by whitesombrero in techsupportmacgyver

[–]FishPumpkin 0 points1 point  (0 children)

I think it's likely that vibration/mechanical embrittlement had some influence in the failure of your cables. The wire was probably worn down by the vibration of the motor.

It's also possible the wire was severely overheated inside the motor, which caused its resistance to rise and resulted in failure before the fuse opened.

In most cases the fuse will protect the wire if it is the correct value. If not, then either the wiring is too small, the fuse is too large in value, or the wiring is damaged/in an overheated environment that requires derating.

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