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Old 09-04-2018, 11:00 AM   #101
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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Originally Posted by vestaviascott View Post
That pin on C20 is almost too tiny to hit, but when I can, I'm getting 0.6 to 0.7 ohms resistance.
That means the big chip runs on 3.3V.
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Old 09-04-2018, 11:02 AM   #102
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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Originally Posted by vestaviascott View Post
Yes, one pin measures 1.2v, the other 4.99v
That may be OK, but not 100% sure until we find the spec sheet.
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Old 09-04-2018, 11:03 AM   #103
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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That means the big chip runs on 3.3V.
Why? What would the resistance read if it ran on say 1.8v or 5v?

I thought we knew it was 3.3v due to its P/N (GH16D)

Last edited by vestaviascott; 09-04-2018 at 11:05 AM..
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Old 09-04-2018, 11:18 AM   #104
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

If the 4.99v was measured on the output pin it is likely ok if it is a TK111XXCS (or R50)
Or from EXAR, SPX5205 pdf
"A bar is added to indicate lead-free parts and can be mistaken as a “1” or an “I”."

If you can, it is best to follow the trace from a pin to nearby connected component to measure the voltage, or use a needle connected to your probe
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Old 09-04-2018, 11:20 AM   #105
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

Here's a pic of the back of the board, do I need to remove the panel?

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Old 09-04-2018, 11:28 AM   #106
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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Why? What would the resistance read if it ran on say 1.8v or 5v?

I thought we knew it was 3.3v due to its P/N (GH16D)
I do not understand your question.
I have you check the resistance between the cap and the output of that RG1 output pad to find out if that big IC where C20 is running on 3.3V from RG1 or not.
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Old 09-04-2018, 02:40 PM   #107
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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I do not understand your question.
I have you check the resistance between the cap and the output of that RG1 output pad to find out if that big IC where C20 is running on 3.3V from RG1 or not.
Ah, I see now (said the blind man), lol. Yep I understand with your explanation. I misunderstood your reasoning earlier <learning>

So, my lesson learned is (correct me if I'm wrong), if there is > 0 resistance between those two paths it means they are connected?

Last edited by vestaviascott; 09-04-2018 at 02:41 PM..
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Old 09-04-2018, 04:26 PM   #108
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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Ah, I see now (said the blind man), lol. Yep I understand with your explanation. I misunderstood your reasoning earlier <learning>

So, my lesson learned is (correct me if I'm wrong), if there is > 0 resistance between those two paths it means they are connected?
Yes, it has direct connection when it show the same resistance as your meter probes resistance..
Look up the spec sheet for that large IC to see what the max Vcc it can handle, it was fed by 7V so it may be damaged.

Last edited by budm; 09-04-2018 at 04:27 PM..
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Old 09-04-2018, 04:36 PM   #109
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

possible data sheets for the ic see r_j previous post
Attached Files
File Type: pdf SPX5205_K_02092016.pdf (903.8 KB, 5 views)
File Type: pdf 435299.pdf (306.2 KB, 4 views)

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Old 09-05-2018, 08:29 AM   #110
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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Yes, it has direct connection when it show the same resistance as your meter probes resistance...
OK, confused again. Hopefully I haven't exhausted your patience yet with my continued probing for understanding...

"As your meter probes resistance" compared to what? I'm measuring the resistance between the output pin of the RG1 IC and the Capacitor, I'm not sure what other measurement I'm comparing that measurement resistance against in order to confirm a connection exists between the capacitor and the IC.

My (extremely) simple-minded understanding was that IF there was any resistance at all between these two components, then they are connected and that was what you wanted to test. However, it sounds like you are saying if, and only if, the resistance measured is the SAME as some other resistance measure then it means a connection exists.

Rather than simply blindly do these experiments, I'm really trying to understand the "WHY" of what I'm doing so that I can learn from the experience.

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Old 09-05-2018, 01:52 PM   #111
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

Put your meter in 200 Ohms scale or the lowest scale it has then touch the two meter probes together to read the probe wires resistance, I.E. it may show 0.50 Ohms.
The lets say you checking the resistance of 0.47 Ohms resistor, the meter will not show 0.47 Ohm, it will show 0.97 Ohms, which means you need to subtract the probe wires resistance from the reading to get the resistor resistance, so 0.97 - 0.5 = 0.47 Ohms.
Do the experiment with a piece of copper wire by testing the resistance between point A (one end of the wire) and point B (another end of the wire) that is connected together by copper trace on the board or by a short piece of wire, it shows 0.5 Ohms, then you know that the connection between point A and point B is direct connection, then you can do visual inspection to see if that is true or not. BTW, always use the lowest Ohm scale for checking the connection between point A and point B
You can then replace a piece wire with resistor, I.E. 100 Ohms, so one end of the resistor is Point A, another end of the resistor is point B and see what you read on your meter, get the picture?
That output pin of BAD RG1 goes to may parts of the circuit, we already verify that it goes to positive pin of the C20 by checking the resistance and it shows < 1 Ohms using your meter in the lowest Ohm scale. I set my meter to manual mode at the lowest Ohms scale for this kind of test.

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Old 09-05-2018, 02:09 PM   #112
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Default Re: Like New Nautilus Exercise Bike has Dead Panel

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Originally Posted by vestaviascott View Post
OK, confused again. Hopefully I haven't exhausted your patience yet with my continued probing for understanding...

"As your meter probes resistance" compared to what? I'm measuring the resistance between the output pin of the RG1 IC and the Capacitor, I'm not sure what other measurement I'm comparing that measurement resistance against in order to confirm a connection exists between the capacitor and the IC.
Lets get terminology straight...

A "resistance" of 0 means a perfect/ideal connection: "NO resistance".

An infinite resistance (often indicated by a "blanked" display or portion thereof) indicates perfect INSULATION -- no connection at all.

Trace the foils VISUALLY. I.e., you now KNOW that point A is connected (electrically) to point B. Now, put the meter on those two points -- you should see "close to" zero resistance. A signal would cheerfully flow from A to B as there is nothing IMPEDING its flow.

Now, find two points that you know are not directly connected. E.g., hold the probes in mid air, untouching, and see what meter says. A signal would have a helluva time getting from probe 1 to probe 2!

In reality, you will see something in-between these extremes for any two points on the circuit board. If you probe across R8 (near U1 in photo of post #62) you'll see something different than if you probe across R18 (same photo).

In these two cases (R8 & R18), you can see that there is a resistor between your probes. But, if you happened to probe between the left side of C7 and that feed-thru just to the southwest of R18, you'll get the same reading as if you had probed directly across R18. The point is, you may not be able to see R18 or even know that it exists when you probe two points in the circuit.

Hence my preference for newbies to visually trace conductors instead of relying on the meter -- which can be misleading!

For example, connect the probes on the two pins of C17 (tall black capacitor near the pair of ribbon cables). Watch the meter WHILE you are making the connection. Now, swap the probes and make the connection, again (while watching). Find an even bigger cap and try it again. Ditto with a small one.

If, for example, you put the probes on the power conductors entering the board, you will see the "net" resistance of the entire circuit board. Depending on the board, this can be very low -- yet, most often, you wouldn't consider it a "short".

Quote:
My (extremely) simple-minded understanding was that IF there was any resistance at all between these two components, then they are connected and that was what you wanted to test.
An absence of resistance indicates a connection. A resistance of "0".

Quote:
Rather than simply blindly do these experiments, I'm really trying to understand the "WHY" of what I'm doing so that I can learn from the experience.
Again, this is why I'd prefer you use your eyes to determine "where signals go". Once you get a feel for where they are LIKELY to go, you can bring the meter into play as a shortcut to VERIFY those deductions. By then, you will hopefully understand how the meter can confirm (and deceive!).
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