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Old 09-01-2018, 04:02 PM   #25
Curious.George
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Join Date: Nov 2011
Posts: 1,304
Default Re: Like New Nautilus Exercise Bike has Dead Panel

Quote:
Originally Posted by vestaviascott View Post
First thing I would like to determine is if the board is getting power. To do that, I'm first going to measure the voltage of the red wire (#2) at the top console harness. I believe I should expect from 5-9 volts if everything downstream has proper continuity.
Adopt some convention for referencing signals, pin numbers, connectors, etc. E.g., there are several "#2" pins -- the "10 pin red connector" appears to be the reference frame for your choice of "#2". But, there are other places where you may, eventually, be referencing (connector) pin numbers.

E.g., HD5 and HD6 each have NOTHING in the pin #2 position -- and HD1 has nothing in ANY position!

Quote:
So, for the test, on the DMM, black lead to ground wire (#5) and red lead to red wire (#2), and I should get a voltage reading when the power adapter is plugged in. All good to start?
Yes, just be careful not to let the probe slip off and potentially short out "something".

As there is nothing (electrically) attached to the red wire (isn't it Red w/white tracer?), there is nothing drawing current from the power adapter. So, there will be no voltage drop along the length of the cable. What you saw AT the adapter should also be present "exactly" at the red connector (assuming you are probing it before connecting to the circuit board).

Once you mate the connector to the PCB, there will be some load on the power supply so you might see a TINY voltage drop at the circuit board end of the wire. This is because wire has resistance and, therefore, current flowing through it (to power the circuit board) causes a potential to be developed across it. "IR loss" (I=current, R=resistance, I*R=volts)

One of the first things you should do is verify the connection of the "ground wire" to the "large expanses of foil" (e.g., that cross-hatched area and anything electrically tied to it) on the circuit board. This will give you a variety of other places where you can make a connection to "ground" (convenience).

Quote:
Once that test is complete, and assuming I get expected voltage, should I just pull this board and measure from the solder joints on this other side of these wires?
Visually trace the power signal as it transitions ONTO the circuit board. It will be a large-ish trace so relatively easy to follow. See where it goes. Pay particular attention to any devices that it appears to pass THROUGH (i.e., places where the only way for power to continue onto the board is THROUGH that device). Probe the "far side" of those device(s) to verify that power is, in fact, passing through. If not, you need to understand if the device/component has failed (e.g., fuse) and is interfering with power being available for the board or if the device is supposed to intentionally interrupt the flow (e.g., a device used as a "switch"). In the latter case, you'd need to figure out how to "turn on" that switch. Or, if it is there to somehow condition the power (e.g., a voltage regulator).

Goal, here, is to identify the OBVIOUS places where power should flow and verify that it does, in fact, do that.
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