http://www.johnsonelectric.com/en/products/motion/dc-motors/datasheets/HC685LG-011-imperial.pdf

This is the turning motor in the Logitech G25, not the vibration motor. I basically had it fixed, but didn't pull the power on it and the circuit board hit a piece of metal and at the very least arced. I am trying to narrow down from the easiest to the hardest components that could cause this. The weird part is on that board the only parts that could have made contact is like 3 diodes and 2 resistors (2 resistors are good, as are the MOSFETs).

Please spare me the BS/Trolling posts, I need some actual ideas. I've checked everything I can think of and so far nothing is working.

Basically the G25 works like this: there is a "rack and pinion gear" that slides against a flat slotted plate that meshes with the steering wheel. You have two motors, one is only force feedback while the other is only involving in calibrating/resistance/turning the wheel. I notice there is way too much resistance once I have it back together, so I take it back apart. When I removed the motor assembly from the gears everything was fine. I put it back together and it still felt fine, as soon as I threw power to it the problem returned. Could you short out a DC Motor at such a low voltage? Blown diode? It feels like it is harder to turn clockwise than it is counter, that is what makes me think I have a bad diode and one of them is reading the same resistance in both directions (which makes no sense to me).

If you really want to see what is inside there, everything is here: https://www.dropbox.com/s/nxs2imi2xh3j8mj/logitech_repair.pdf?dl=0


Thanks for any help.

12/5/2014 12:55:28 PM

As a general rule, you should troubleshoot problems you know you have (harder to turn clockwise than counter-clockwise) and not problems you think you have (something is "shorted").

My first thought is that whatever the controller uses for wheel position feedback isn't working correctly. This could be because you broke it, reassembled it incorrectly, or it needs to be calibrated.

With respect to arcing and sparking: anything in the current path is a potential victim and not just the components that did the actual arcing and sparking.

And, of course, you may have botched whatever repair it is you were doing.

12/6/2014 7:10:37 PM

You could have blown a diode allowing power to flow to the motor, the motor is trying to slightly turn one way with that leakby power which would explain why it resists harder turning one way and feels slightly easier the other. At least, thats one theory. I doubt you shorted the 24vdc motor unless you put straight 120vac across it during your arc for a good bit of time, easiest way to tell is (if you dont have some sort of benchtop power supply or 24v wall wart, take the motor out and put two 9volt batts together across it, or a costco-sized pack of AA's if you have them on hand, to see if it spins up decently. Alternatively you can check for intermittent contiunity across the motor terminals. IIRC, as you spin a brushed dc motor you should have normal continuity (measuring across the terminals) that breaks periodically as the commutator sections make/break with the brushes/terminals. No continuity at all would indicate you overpowered the motor and may have burnt up the wiring in the windings.

12/7/2014 1:52:17 AM

Thanks for the advice guys, I'll update again once I have time to work on it some more.

One other note, why is the motor still like this after no power has been applied for over 2 days??

I just noticed it is as soon as I unplug the main power connection right before the diodes and MOSFETs to the motor from the primary PCB is how I restore normal movement.

So I have a capacitor holding charge that long maintaining the resistance. Someone correct me if I am wrong here, but a diode only should read in one direction, that is the entire point. So if I have two who are doing that and then I have another reading in both directions, there is a pretty good chance that could be the issues. The MOSFETs all read fine as does every SM part I bothered to check, was like ~30.


Let me just give you the diode resistance for all 3:

D1: 7.7 M Ohms (Flip VMM Probes) 10.4 M Ohms
D2: 1.9 Ohms (Flip VMM Probes) 1.9 Ohms
D3: 7.75 M Ohms (Flip VMM Probes) 10.42 M Ohms




[Edited on December 7, 2014 at 9:25 AM. Reason : _]

12/7/2014 9:01:53 AM

One other thing to note is that Diode 1 and Diode 2 are the two diodes tied to the power connections of the motors and Diode 2 (the one with odd values) just happens to be the one that goes to the screwed up motor. I'm going to desolder it and get the full PN and get one sent.

12/7/2014 9:51:15 AM

Are you taking these measurements with the components still in the circuit? Is the power on or off? Are you using the diode check mode on the multimeter?

12/7/2014 10:20:47 AM

^^Good questions to answer, if you are measuring these still on the PCB you could be measuring other components own/upstream of he diodes. But based on your measurements though, I'd agree Diode 2 is shot, it's essentially acting as a resistor now. If nothing else it's worth a shot, as those cost probably less than a dollar, order enough to replace all of them just incase, would still be less than a taco bell combo.

12/7/2014 12:44:54 PM

Yes the diodes are still in the circuit, but obviously these are through hole components. So I am measuring right at the ends of the diodes right where the lead comes out.

I can give you diode measurements and it will tell you the same thing

D1 and D3 measure .5V in one direction and .88V in the other

D2 measures 0V both ways.


Here is the circuit:




I'm calling D1 and D3 the diode to the left and the one underneath the motor connections. D2 being the diode that is on the right side where the motor involved in movement is located.

12/7/2014 2:02:09 PM

If the diode is in the circuit, you're measuring across the diode and everything parallel with the diode. You need to lift leads.

12/7/2014 5:00:28 PM

That is easier said that done and that is what I tried first off. Desoldering didn't work, using a soldering iron and a pump is partially working, but it shouldn't take this much to remove something so small. I've built multiple guitar effect pedals and done hardware mods on PC equipment, I know how to use the tools. I have no idea what is holding these in so tight.

12/7/2014 5:35:26 PM

Ok so I just clipped D2 out and it reads 0.593V and 16.29 M Ohms now... So this may not be as simple as I hoped.


This is the exact part: http://www.mouser.com/ProductDetail/Vishay-Semiconductors/P6KE27A-E3-54/?qs=ACmI7jQvrjpfD30WBMpiNw%3D%3D

Vishay P6KE27A Diode

Quote :

"Manufacturer Vishay Product Category TVS Diodes - Transient Voltage Suppressors RoHS E Polarity Unidirectional Operating Voltage 23.1 V Breakdown Voltage 25.7 V to 28.4 V Clamping Voltage 37.5 V Peak Surge Current 16 A Series P6KE Package / Case DO-204AC Minimum Operating Temperature - 65 C Maximum Operating Temperature + 185 C Dimensions 3.6 mm Dia. x 3.6 (Max) mm W x 7.6 mm L Packaging Reel Termination Style Axial Brand Vishay Semiconductors Mounting Style Through Hole Peak Pulse Power Dissipation 600 W Standard Pack Qty 4000 Tradename TransZorb"

[Edited on December 7, 2014 at 9:00 PM. Reason : _]

12/7/2014 8:44:54 PM

Stick to voltage drop checks of diodes.

I don't know why you thought it was going to be easy. You're troubleshooting a complicated circuit by easter egging.

12/8/2014 1:01:55 AM

It just made sense the diode on the side of the motor screwing up would give a weird value and then I could just swap it out. However that was me being hopeful. I'm wondering if I should open that motor up to check the brushes.

Is there anything you can check while it is still in the circuit and get accurate readings?



[Edited on December 8, 2014 at 5:53 AM. Reason : _]

12/8/2014 5:50:20 AM

The make SM resistor checkers, so can you check resistors while still in the circuit?

http://www.qsource.com/p-10454-excelta-tm-500-intellitweeze-r-c-l-meter.aspx?utm_source=Google&utm_medium=Shopping&utm_campaign=Shopping&gclid=Cj0KEQiAtZWkBRC9ibSfhoKEyLYBEiQA5fDxkY5-c3_JHNeZLFQ2zxwNteXbLvjh8vbcj_LEH9C0pi0aAgsV8P8HAQ


Now that thing is retarded expensive, but they are testing inside the circuit.

12/8/2014 6:15:29 PM

Quote :

"If the diode component is in the circuit, you're measuring across the diode component and everything parallel with the diode component."

[Edited on December 9, 2014 at 12:53 AM. Reason : Are you really an EE?]

12/9/2014 12:52:29 AM

I am assuming you are talking about me. I matriculated and then had to pull out that next semester when you are starting ECE 109, 200, 209 for a medical withdraw due to chronic neck pain. I should be returning by the Summer Sessions or the next Fall. The funny part is I turned in my AC to DC converter for the lab project early and made a 90 something in there, but never even had a chance at the final in ECE 200.

So technically yes, but fundamentally no. I do a lot of electronics mods and shit, but never had to debug a circuit before. I always thought you could not measure components while still in the circuit unless you knew the suspected given value of the component you are measuring beforehand, but when I ran across that the other day I was like "hmmmm".

I would appreciate some help and move on from BlackDog didn't get truly through his 2nd Sophomore Semester before having to withdraw. I can't go through this circuit clipping off every component, so how do you troubleshoot something like this?

With those diodes only being $0.62/ea I will replace them and see if I get lucky, but aside from that what can I do? I can do SM soldering, I just have no idea how to debug a circuit like this and that is why I made the thread.



[Edited on December 9, 2014 at 3:50 AM. Reason : can't]

12/9/2014 3:46:45 AM

Quote :

"D1: 7.7 M Ohms (Flip VMM Probes) 10.4 M Ohms D2: 1.9 Ohms (Flip VMM Probes) 1.9 Ohms D3: 7.75 M Ohms (Flip VMM Probes) 10.42 M Ohms"

did you have power running to the circuit board when you took those readings?

12/10/2014 10:32:12 AM

no

12/14/2014 11:14:08 AM

Did you ever isolate/remove the motor and test it?

12/14/2014 2:39:29 PM

Yea I hooked up the VMM to it and the ohms readings I was getting (~29.5) were inside the spec of the motor according to them. (2nd link)

12/14/2014 3:40:07 PM

You need to power it up and measure the voltage at various points and see if it agrees with what you think it should be. You cant passively measure stuff in circuit unless you understand the circuit well.

Try drawing a schematic of the circuit. With enough beeping around you can do it. Then understand it, then check voltages.

12/14/2014 6:18:58 PM