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Old 05-29-2019, 04:21 PM   #31
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


those chips looks normal, the board probably had a varnish over it so they look weird.
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Old 05-29-2019, 09:34 PM   #32
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


I agree with @carmusic . The chips don't look bad or damaged.

From the markings, the 14-pin chip appears to be a hex Schmitt Trigger, which is used to clean up noisy signals.

Also from the marking, I think you are right that the 8-pin chip is a RS485 interface chip.
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Old 05-29-2019, 10:02 PM   #33
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by RAL238 View Post
From the markings, the 14-pin chip appears to be a hex Schmitt Trigger, which is used to clean up noisy signals
Interesting that you mention noisy signals. I just picked up a Meade Autostar telescope system from thrift store today. Cost me all of $2. Crazily, it fired right up when I got it home and put batteries in, and it even slews! At least in vertical direction but not horizontal. So, long story short, in searching for a fix for the horizontal slewing issue (turns out its loose gears), I came across this page that discusses how the servo motor noise can feed back to the motor control board and cause weirdness:

http://www.data-plumber.com/dsmotors.htm


I'm wondering if you think that may be possible cause here and whether the inline resister+capacitor fix may help resolve the problem:



BTW, that motor control board I ordered that said "In stock" is, as luck would have it, back ordered.

Last edited by homeimproverjoe; 05-29-2019 at 10:07 PM.
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Old 05-29-2019, 10:22 PM   #34
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by homeimproverjoe View Post
I'm wondering if you think that may be possible cause here and whether the inline resister+capacitor fix may help resolve the problem:

BTW, that motor control board I ordered that said "In stock" is, as luck would have it, back ordered.

From what you've described, I don't think that sort of noise is causing your problems, since it seems that the motor isn't getting the right voltage under load.
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Old 05-29-2019, 11:32 PM   #35
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by RAL238 View Post
From what you've described, I don't think that sort of noise is causing your problems, since it seems that the motor isn't getting the right voltage under load.
Could the noise feedback be increasing as the load on the motor gearing increases, perhaps causing one of the sensors or ICs on the motor control board to send a lower voltage due to the excess noise?
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Old 05-30-2019, 09:01 AM   #36
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by homeimproverjoe View Post
Could the noise feedback be increasing as the load on the motor gearing increases, perhaps causing one of the sensors or ICs on the motor control board to send a lower voltage due to the excess noise?

Without a schematic, it's very hard to be certain about the cause of the problem. The Schmitt triggers wouldn't be my first suspect. To me, it looks more like a problem with the circuit supplying the power than the controls. Admittedly, that's based on very limited information.
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Old 05-30-2019, 09:36 PM   #37
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


I believe I found the datasheet for the 8 pin chip with the notched top and curious circle shape at the top left:



http://rohmfs.rohm.com/en/products/d...c/bd621x-e.pdf
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Old 05-30-2019, 10:31 PM   #38
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by homeimproverjoe View Post
I believe I found the datasheet for the 8 pin chip with the notched top and curious circle shape at the top left:



http://rohmfs.rohm.com/en/products/d...c/bd621x-e.pdf

What is it that you see on the 8-pin package markings that make you think it is this motor driver chip?
In the photo that you posted previously, I see a Texas Instruments logo on the middle line and 751678 or maybe a 75167B on the top line, which makes me think it is this chip:

http://www.ti.com/lit/ds/symlink/sn65176b.pdf

According to the motor driver chip data sheet (pg 16), it should have a 6210 or 6211 on the top line. I don't see that in the photo.
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Old 05-30-2019, 11:15 PM   #39
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by RAL238 View Post
What is it that you see on the 8-pin package markings that make you think it is this motor driver chip?
In the photo that you posted previously, I see a Texas Instruments logo on the middle line and 751678 or maybe a 75167B on the top line, which makes me think it is this chip
I'm referring to the chip under the resistance motor control socket. it has no discernable writing on it, but the shape and the circular indention are in the exact same as the chip in the datasheet diagram.

Here is the shot of the chip on the board:



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Old 05-31-2019, 07:42 AM   #40
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by homeimproverjoe View Post
I'm referring to the chip under the resistance motor control socket. it has no discernable writing on it, but the shape and the circular indention are in the exact same as the chip in the datasheet diagram.

Here is the shot of the chip on the board:




Ok, now I understand. I had misinterpreted your photos and thought the photo of the 8-pin IC where the writing was visible was the same chip, just at a different angle to make the writing visible.



Can you trace the wiring from pins 1 and 7 to verify that they connect to the motor wires (blue and yellow)? That would be a reasonable confirmation that this is a motor driver chip. If it is, that would be a good first suspect of a bad component.
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Old 05-31-2019, 02:15 PM   #41
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by RAL238 View Post
Can you trace the wiring from pins 1 and 7 to verify that they connect to the motor wires (blue and yellow)?
By that do you mean a visual inspection (the lines are really close and some are obscured by the pin sockets and the chips themselves) or do you mean a DMM continuity test between the pin on the chip and the corresponding pin on the socket connector?

For example, one probe on Pin 1 or the chip and the other on the yellow or blue wire's male lead in the socket connector?

Last edited by homeimproverjoe; 05-31-2019 at 02:19 PM.
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Old 05-31-2019, 02:33 PM   #42
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


There is continuity between pin 1 (Out 1) of the chip and pin 2 (blue motor power wire) of the motor socket connector.

And there is continuity between pin 7 (Out 2) of the chip and pin 1 (yellow motor power wire) of the motor socket connector.

__________

Other continuity paths (i guess this should be predictable?):

Pin 2 (VCC power) > Pin 3 (red power wire)
Pin 3 (VCC power) > Pin 3 (red power wire)

Last edited by homeimproverjoe; 05-31-2019 at 02:52 PM.
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Old 05-31-2019, 11:17 PM   #43
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by homeimproverjoe View Post
There is continuity between pin 1 (Out 1) of the chip and pin 2 (blue motor power wire) of the motor socket connector.

And there is continuity between pin 7 (Out 2) of the chip and pin 1 (yellow motor power wire) of the motor socket connector.

__________

Other continuity paths (i guess this should be predictable?):

Pin 2 (VCC power) > Pin 3 (red power wire)
Pin 3 (VCC power) > Pin 3 (red power wire)

The first thing I would try and determine is whether the motor driver chip is bad, or whether the power or control signals coming in to it are messed up.



I would measure the voltage on pins 2 and 3 when the motor is lightly loaded and working, and then also when it is under a heavy load and not working. If you see the same voltage (5V?) then that suggests that the problem isn't due to a power supply problem. If the voltage on pins 2 and 3 is not 5V (or whatever Vcc is), then the problem is upstream somewhere.



The next possibility is that the control signals to the chip are messed up in some way. That would be the signals on pins 4, 5 and 6. It might be tough to tell if they are ok using a voltmeter since they may be pulsed signals. You would really need a scope to see what they look like.
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Old 06-03-2019, 10:37 PM   #44
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


UPDATE: The new control board is in and she runs like she's 'spose to. I haven't done any pin voltage tests yet to compare the motor controller chip readings. Hope to have some time to do that tomorrow. Just glad I can sell this thing for top dollar now especially with all the time I've devoted to the repair diagnosis.

Thanks for all the help, especially RAL238 for sticking with me over several days of troubleshooting.
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Old 06-03-2019, 10:40 PM   #45
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Re: Elliptical Machine - Panel sending too low voltage to resistance brake motor


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Originally Posted by homeimproverjoe View Post
UPDATE: The new control board is in and she runs like she's 'spose to. I haven't done any pin voltage tests yet to compare the motor controller chip readings. Hope to have some time to do that tomorrow. Just glad I can sell this thing for top dollar now especially with all the time I've devoted to the repair diagnosis.

Thanks for all the help, especially RAL238 for sticking with me over several days of troubleshooting.

Good job! Glad you got it working.
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