Unusual problem with Hitec HS-325
02-11-2013, 08:53 AM
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Unusual problem with Hitec HS-325
Last weekend i had an unusual problem with the throttle servo of a calmato trainer plane. The servo was a new (out of the box) Hitec hs-325. During fourth flight ,when i gave full throttle to make a loop ,i realized that my engine had stoped responding to my commands. After making planty off cyrcles to burn up the fuel ,i landed the plane safely. Investigation showed that throttle servo was dead. It was not jammed like having stripped gears, just dead.
After returning home i opened up the servo. No stripped gears and no sign of fried electronic components. So i unsoldered the motor of the PCB and tried to power sypply it using a NIMH battery. No move. I supposed it was fried but my multitester showed opencircuit instead of shortcircuit ,which is the usual sign of a fried motor. I thought that brushes were worn out ,so i opened up the motor. What i found was that the brushes and the collector were in perfect contition ,so the problem could not be worn out brushes. I decided to use my multitester directly on the collector sectors to find out that the rotor windings had lost their connectivity. The winding terminals seemed to be well soldered on the collector sectors. No sigh of a broken wire but no sigh of connectivity as well.
Now ,the only thing i can suppose is that the winding wire either was cold-soldered on the collector terminals or it was soldered without removing the winding-wire insulation properly. So ,although that initially it was fine ,after a few flights the winding wire lost its connectivity with the collector sectors.
I use Hitec hs-325 servos for many of my planes and one of my nitro helis ,all of them having many hours of flying and i have never experienced any kind of problems. It is the first time i have an issue using hs-325 (fortunately the throttle). I was considering Hitec servos as very good servos but after that ,i am really concerned. I remind that it is not a classic problem of a fried motor or a fried motor drive. After investigation It is clear that there is a bad soldering issue.
The question is. Is it an isolated incidence or there is something wrong with quality control of newer batch of Hitec servo motors? Who knows?
After returning home i opened up the servo. No stripped gears and no sign of fried electronic components. So i unsoldered the motor of the PCB and tried to power sypply it using a NIMH battery. No move. I supposed it was fried but my multitester showed opencircuit instead of shortcircuit ,which is the usual sign of a fried motor. I thought that brushes were worn out ,so i opened up the motor. What i found was that the brushes and the collector were in perfect contition ,so the problem could not be worn out brushes. I decided to use my multitester directly on the collector sectors to find out that the rotor windings had lost their connectivity. The winding terminals seemed to be well soldered on the collector sectors. No sigh of a broken wire but no sigh of connectivity as well.
Now ,the only thing i can suppose is that the winding wire either was cold-soldered on the collector terminals or it was soldered without removing the winding-wire insulation properly. So ,although that initially it was fine ,after a few flights the winding wire lost its connectivity with the collector sectors.
I use Hitec hs-325 servos for many of my planes and one of my nitro helis ,all of them having many hours of flying and i have never experienced any kind of problems. It is the first time i have an issue using hs-325 (fortunately the throttle). I was considering Hitec servos as very good servos but after that ,i am really concerned. I remind that it is not a classic problem of a fried motor or a fried motor drive. After investigation It is clear that there is a bad soldering issue.
The question is. Is it an isolated incidence or there is something wrong with quality control of newer batch of Hitec servo motors? Who knows?
02-11-2013, 11:59 AM
#2
Senior Member
RE: Unusual problem with Hitec HS-325
ORIGINAL: bladeskiller
Last weekend i had an unusual problem with the throttle servo of a calmato trainer plane. The servo was a new (out of the box) Hitec hs-325. During fourth flight ,when i gave full throttle to make a loop ,i realized that my engine had stoped responding to my commands. After making planty off cyrcles to burn up the fuel ,i landed the plane safely. Investigation showed that throttle servo was dead. It was not jammed like having stripped gears, just dead.
After returning home i opened up the servo.
No stripped gears and no sign of fried electronic components. So i unsoldered the motor of the PCB and tried to power sypply it using a NIMH battery. No move. I supposed it was fried but my multitester showed opencircuit instead of shortcircuit ,which is the usual sign of a fried motor. I thought that brushes were worn out ,so i opened up the motor. What i found was that the brushes and the collector were in perfect contition ,so the problem could not be worn out brushes. I decided to use my multitester directly on the collector sectors to find out that the rotor windings had lost their connectivity. The winding terminals seemed to be well soldered on the collector sectors. No sigh of a broken wire but no sigh of connectivity as well.
Now ,the only thing i can suppose is that the winding wire either was cold-soldered on the collector terminals or it was soldered without removing the winding-wire insulation properly. So ,although that initially it was fine ,after a few flights the winding wire lost its connectivity with the collector sectors.
I use Hitec hs-325 servos for many of my planes and one of my nitro helis ,all of them having many hours of flying and i have never experienced any kind of problems. It is the first time i have an issue using hs-325 (fortunately the throttle). I was considering Hitec servos as very good servos but after that ,i am really concerned. I remind that it is not a classic problem of a fried motor or a fried motor drive. After investigation It is clear that there is a bad soldering issue.
The question is. Is it an isolated incidence or there is something wrong with quality control of newer batch of Hitec servo motors? Who knows?:
Last weekend i had an unusual problem with the throttle servo of a calmato trainer plane. The servo was a new (out of the box) Hitec hs-325. During fourth flight ,when i gave full throttle to make a loop ,i realized that my engine had stoped responding to my commands. After making planty off cyrcles to burn up the fuel ,i landed the plane safely. Investigation showed that throttle servo was dead. It was not jammed like having stripped gears, just dead.
After returning home i opened up the servo.
No stripped gears and no sign of fried electronic components. So i unsoldered the motor of the PCB and tried to power sypply it using a NIMH battery. No move. I supposed it was fried but my multitester showed opencircuit instead of shortcircuit ,which is the usual sign of a fried motor. I thought that brushes were worn out ,so i opened up the motor. What i found was that the brushes and the collector were in perfect contition ,so the problem could not be worn out brushes. I decided to use my multitester directly on the collector sectors to find out that the rotor windings had lost their connectivity. The winding terminals seemed to be well soldered on the collector sectors. No sigh of a broken wire but no sigh of connectivity as well.
Now ,the only thing i can suppose is that the winding wire either was cold-soldered on the collector terminals or it was soldered without removing the winding-wire insulation properly. So ,although that initially it was fine ,after a few flights the winding wire lost its connectivity with the collector sectors.
I use Hitec hs-325 servos for many of my planes and one of my nitro helis ,all of them having many hours of flying and i have never experienced any kind of problems. It is the first time i have an issue using hs-325 (fortunately the throttle). I was considering Hitec servos as very good servos but after that ,i am really concerned. I remind that it is not a classic problem of a fried motor or a fried motor drive. After investigation It is clear that there is a bad soldering issue.
The question is. Is it an isolated incidence or there is something wrong with quality control of newer batch of Hitec servo motors? Who knows?:
"throttle servo of a calmato trainer plane. The servo was a new (out of the box) Hitec hs-325. During fourth flight ,"
The Calmato is a very old model, how long had it been sitting around? perhaps the throttle rotor was gummed up
with hydrogenated castor oil causing the servo to be close to stall or stalled and burn out faster than usual.
As you have some knowlegde of electronics and have voided the warranty, for the benefit of readers:
. Servo - How to Diagnose Servo Failures & Repair Servo
What battery was beng used to power the servo?
. Servo - Operating Voltage Range - (Hitec) usuage with NiMH, Lipol & A123 batteries.
What Tx &Rx and resolution setting thereof?
. Servo - Burnout. Cause & Prevention
. BURN IN - Aging of RC Transmitter, Receiver & Servo components
Much more information available under sub sections
"Glitches & Jitter in Receiver, Servo & ESC - Causes and Cures"
"Servo - Alterations, Calculators, Databases, Leads, Repairs, Convert to an ESC or winch & FAQ."
below
"Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links
Alan T.
02-11-2013, 01:49 PM
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RE: Unusual problem with Hitec HS-325
The plane is new. I was the lucky man who won it during a "new year cutting pie" event. The engine is also a new out of the box GX-46 and the throttle barell was not gummed up. No mechanical issues. The servo is also new ,out of the box as i have written. Battery is 4 cells NIMH (4.8 volts nominal) and the receiver is futaba r617.
The PCB is fine. The problem is the motor. I have soldered another motor just for testing (from an old hs-325 having stripped gears) and the servo is now just fine.
Anyway, when a motor gets fried either due to overvoltage or due to mechanical issues it dosen't behave like this. I remind that brushes and collector were found in perfect contition and measuring winding resistance directrly through the collector sectors it was infinite. To my experience ,it is not the case of a fried motor. Fried winding behaves as a shortcircuit not as an opencircuit when measured through collector sector terminals.
It is definitely a bad motor issue. More accurately bad soldering issue. I want to believe that it was just an isolated case. That's because i use this kind of servo for years in many planes using either 4.8 volts NIMH or 2cell A123 with a diode in series (5.8 volts under load) without any issues and i consider it as a very good analog servo.
The PCB is fine. The problem is the motor. I have soldered another motor just for testing (from an old hs-325 having stripped gears) and the servo is now just fine.
Anyway, when a motor gets fried either due to overvoltage or due to mechanical issues it dosen't behave like this. I remind that brushes and collector were found in perfect contition and measuring winding resistance directrly through the collector sectors it was infinite. To my experience ,it is not the case of a fried motor. Fried winding behaves as a shortcircuit not as an opencircuit when measured through collector sector terminals.
It is definitely a bad motor issue. More accurately bad soldering issue. I want to believe that it was just an isolated case. That's because i use this kind of servo for years in many planes using either 4.8 volts NIMH or 2cell A123 with a diode in series (5.8 volts under load) without any issues and i consider it as a very good analog servo.
02-11-2013, 05:29 PM
#4
Senior Member
RE: Unusual problem with Hitec HS-325
ORIGINAL: bladeskiller The plane is new. I was the lucky man who won it during a "new year cutting pie" event. The engine is also a new out of the box GX-46 and the throttle barell was not gummed up. No mechanical issues. The servo is also new ,out of the box as i have written. Battery is 4 cells NIMH (4.8 volts nominal) and the receiver is futaba r617.
The PCB is fine. The problem is the motor. I have soldered another motor just for testing (from an old hs-325 having stripped gears) and the servo is now just fine.
Anyway, when a motor gets fried either due to overvoltage or due to mechanical issues it dosen't behave like this. I remind that brushes and collector were found in perfect contition and measuring winding resistance directrly through the collector sectors it was infinite. To my experience ,it is not the case of a fried motor. Fried winding behaves as a shortcircuit not as an opencircuit when measured through collector sector terminals.
It is definitely a bad motor issue. More accurately bad soldering issue. I want to believe that it was just an isolated case. That's because i use this kind of servo for years in many planes using either 4.8 volts NIMH or 2cell A123 with a diode in series (5.8 volts under load) without any issues and i consider it as a very good analog servo.
The PCB is fine. The problem is the motor. I have soldered another motor just for testing (from an old hs-325 having stripped gears) and the servo is now just fine.
Anyway, when a motor gets fried either due to overvoltage or due to mechanical issues it dosen't behave like this. I remind that brushes and collector were found in perfect contition and measuring winding resistance directrly through the collector sectors it was infinite. To my experience ,it is not the case of a fried motor. Fried winding behaves as a shortcircuit not as an opencircuit when measured through collector sector terminals.
It is definitely a bad motor issue. More accurately bad soldering issue. I want to believe that it was just an isolated case. That's because i use this kind of servo for years in many planes using either 4.8 volts NIMH or 2cell A123 with a diode in series (5.8 volts under load) without any issues and i consider it as a very good analog servo.
"the odd rare fallure occurs with every known brand of servo." and given Hitec's very good service reputaton,
am sure a replacement would have been provided if service
had been emailed and above reported direct to them, before the servo was stripped..
Since post #2, have just read an interesting post in answer to a query of another major brand's receiver
. Electronics - Expectations
"I left my iPhone on my dash, in my truck, in August, and it shut down on me. Must be a apple issue. I must call them in the morning.
Seriously guys. You are talking about a product and a electronic product at that.
It is a irrational expectation to believe that it will never happen to a certain product.
There are 2 facts that are always over looked.
The first one is that regardless of he brand or the product there will be a few that slip through Q.C. and have a good chance in failure.
The second is that >95% of the time the user is at fault.
We have developed in to a society where everything is done for us, and nothing is ever our fault.
My suggestions all those that have had a issue. Get over it.
There is a chance it could happen you just don't want I be the one.
Stop putting your Rx's in your ovens and your equipment in conditions that are set up to purposely make them fail.
Odds are they will.
When you have a problem, deal with the company producing said product and hope for the best.
You can not expect them to buy every person with a complaint a new 40% plane because the local RC flying clubs
CSI team found that the fuel dot came loose caused the crash.
If your car breaks down you have it fixed. How is anything else any different. "
Alan T.
Alan's Hobby, Model & RC FAQ Web Links
02-11-2013, 11:40 PM
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RE: Unusual problem with Hitec HS-325
We are talking about a 17 euros servo. It would cost to me more to send in back to Hitec service than just buying a new one. Furthermore, as an electronic technician , i had the curiocity to find out by my shelf what exactly was the cause of the failure.
Given that such an issue into the motor could not be a result of misusing, i decided to crosscheck if it's a known issue or it's just a piece that "escaped the net" of Q.C.
Given that such an issue into the motor could not be a result of misusing, i decided to crosscheck if it's a known issue or it's just a piece that "escaped the net" of Q.C.
