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General Shortouts and Opens

roughshawd

Jul 13, 2020
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Expecting a great turnout for this thread!! I am at odds with this discussion already, so maybe we can lose the rhetorical whoo-haw and just think for a minute.

When a short occurs, it usually dumps a bunch of power to ground causing some things the board runs, to just quit working.
Sometimes other things to appear to work a lot better than normal.
It also causes things to burn up now and again.

But when an Open happens, it usually causes the majority of the devices beyond that series connection to just stop, and sometimes everything just quits. There is that off chance that the designer built the circuit from the ground-up, and everything is still working just needs a smack on the side to get it going.

I would assume that in the case of a testing for power leaks, that someone might find a direct drain of volts, as a short circuit and an open as a dead or zero voltage and presumably un-defined condition.

I have found many shorts in my amature work. Most were not white lies, but loose connections or direct shunts from a power line to a ground.
Most of these devices worked, but certain aspects were not proper, that is to say that the short was stopping some of the bells and whistles to fail.
Sometimes the device would run for a couple seconds and then fail.

I say shorts, not because its laundry day, but because an open is a loss of power, while these devices are still showing power.
The main argument here is that an open in a dedicated electronic circuit does not generally shut off anything ahead of the open but only the lossy or negative side, so it's really hard to tell sometimes whether it's a short or an open.

I was counting on you pro engineers to design stuff that has color codes... really bad idea cause some are color blind(My dad and sister are sepia)
Anyway when I look at a wiring diagram to trace for shorts and opens, it's not easy to open a stainless case that is sealed at the factory, or remove a plastic that is glued with some form of sealing waterproof goop harder than grandmas boobs, just so I can trace a wire.
I can utilize a set of long alligator clips from both ends of the leads, but today they use multiple wires in connectors and that method doesn't always work.

All things said... I am tracing a device for something that is wrong. Not messing with electricity. There is a direct 110v drain from the top of the power caps to the case. Not so good on a fridge!

Tell me about shorts that don't stay white when you bleach them please !!!!
I have tested other devices and found this same power anolemna.
I need to know if I should find this short, leave it alone or something else.
Please don't add to the problem by telling me you need a serial number and the model ID. That just adds to the problem.
I am trying to fix it.
 

Martaine2005

May 12, 2015
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Long winded way to ask a question, but grandma’s boob made me laugh.
Here’s my take on it. The capacitor might be connected to 100V negative supply with respect to ground. Some amplifiers heat sinks are the same. You’ll get a decent whack from touching them.
A short OR a short circuit?
A short can make things work like a switch. A short circuit is for example when positive meets negative directly and something goes bang!.
Think of closed circuit and open circuit like a light switch.

Martin
 

kellys_eye

Jun 25, 2010
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All I can say is:

"step back from the equipment and drop that test meter"
 

roughshawd

Jul 13, 2020
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Jul 13, 2020
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short sentence first...
a couple connectors got broke, and the wiring connector is gone, so I can't tell which wires connect to which. The wiring diagrm stipulates options on a white/w Yellow wire in the connector. It is a DC door heater. One down, three to go!!! (I think!)
 

roughshawd

Jul 13, 2020
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I looped the test wire around the fridge to test the continuity of a white/yellow wire I found on the board. great continuity there, it is definitely connected somewhere in the case 1 ohm. Thats really good continuity! So when I trace the circuit through what is supposed to be the optional door heater... 12ohms just like there was a heater in there, so I am now assuming that the heater option was installed on this fridge(they use the heater to defrost it regularily!) I am now going to test the other lead(gray wire from the case, not the ones that go into the door hinge) and see it I get continuity from the terminator of the door heater lead. if I get the 12 ohms I would say yes.... thats the heater loop, but if I get infinity, then I would say that is not the looping lead from the heater. The wiring diagram shows the circuit just loops from the board connector out through the heater and back to the board and to the connector... I guess pull the connector off the board before I test the loop just to make sure the 12 ohms isn't the board itself.
 

roughshawd

Jul 13, 2020
264
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Jul 13, 2020
Messages
264
I looped the test wire around the fridge to test the continuity of a white/yellow wire I found on the board. great continuity there, it is definitely connected somewhere in the case 1 ohm. Thats really good continuity! So when I trace the circuit through what is supposed to be the optional door heater... 12ohms just like there was a heater in there, so I am now assuming that the heater option was installed on this fridge(they use the heater to defrost it regularily!) I am now going to test the other lead(gray wire from the case, not the ones that go into the door hinge) and see it I get continuity from the terminator of the door heater lead. if I get the 12 ohms I would say yes.... thats the heater loop, but if I get infinity, then I would say that is not the looping lead from the heater. The wiring diagram shows the circuit just loops from the board connector out through the heater and back to the board and to the connector... I guess pull the connector off the board before I test the loop just to make sure the 12 ohms isn't the board itself.
My rule of thumb is white to white, brown to brown and red to red, it didn't really include any white/yel stripes or purples and pinks in the same terminals on the connectors that connect to grays and whites! ( Alien asumptions can cause severe shocks on reworks )
 
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