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Old Apr 28, 2013, 10:00 PM
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Help!
hitec ac plus x4

Help please burnt resistor on ac dc converter board can somebody please please open up theirs and give me a number of the resistance or a good picture of the resistor I need or if you have a schematic that would work too the resistor I need is number R29 it is close to the transformer on the AC board next to a capacitor I will attach a photo of it
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Old Apr 29, 2013, 07:05 PM
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Originally Posted by car_ramrod View Post
Help please burnt resistor on ac dc converter board can somebody please please open up theirs and give me a number of the resistance or a good picture of the resistor I need or if you have a schematic that would work too the resistor I need is number R29 it is close to the transformer on the AC board next to a capacitor I will attach a photo of it
I hope someone answers! Great idea to ask! I asked Hitec, but they declined to tell me (or let me see the schematic). They only charge $25 an hour to fix it, and I doubt it would take more than an hour if the only thing wrong is the resistor. I blew mine out by accidently hooking it up to a car battery backwards. Now the AC power supply doesn't work. I don't think the punishment fits the crime, but fortunately I have a spare AC power supply. Also, I really use the charger all the time, and can't send it away for service even if it only took a couple of weeks.

Someone! Please, open your charger (just remove the screws on the sides that go into the top), and let us know the value of the resistor.
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Old Apr 29, 2013, 07:31 PM
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Thats the exact same scenario they will not tell me the resistor bla bla bla but said they will fix it for free but I cant send it in because I need it I dont know why the hell they did not internally fuse to protect the electronics poor poor engineering bit hopefully someone will open the case and help makes me never want another hitec product my charger is only 3 weeks old too
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Old Apr 29, 2013, 08:04 PM
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Sorry to hear about your misfortune and that a reverse voltage can do significant harm to the Hitec AC+ Quad. For those of us who might be prone to hookup mistakes, there is a very common and simple circuit that can be added to a device that usually prevents reverse hookup damage.

It incorporates a diode and a fuse to protect the device. A fuse is always an important part of a DC circuit so there should be one attached to the battery or DC supply output or positive terminal. Then, in the charger across the power input leads add a diode adequately large enough to blow the fuse with its output lead to the positive and input lead to the negative so that it conducts and blows the fuse if the leads are hooked up wrong polarity.

Most quality devices employ such a diode on their dc input leads but the diode is of no use unless it has a fuse to blow. The Hitec charger may have such a diode...if so, to provide reverse polarity protection, the source needs to be fused otherwise the diode can't save the day.
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Old Apr 29, 2013, 08:09 PM
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Originally Posted by car_ramrod View Post
Thats the exact same scenario they will not tell me the resistor bla bla bla but said they will fix it for free but I cant send it in because I need it I dont know why the hell they did not internally fuse to protect the electronics poor poor engineering bit hopefully someone will open the case and help makes me never want another hitec product my charger is only 3 weeks old too
You are right that a fuse and diode could have been added to the charger to prevent reverse hookup damage. And there may in fact be a diode... who knows. Convention however is that fusing is done at the source supply.
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Old Apr 29, 2013, 08:27 PM
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I suppose we might think of the resistor as a hard-to-replace fuse. The aggravating part is I'm quite capable of replacing a resistor if I only knew the specs, but as car_ramrod's picture shows, the resistor completely disappeared. I also agree the engineering should have prevented catastrophic damage from such a common mistake.
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Old Apr 29, 2013, 08:40 PM
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Originally Posted by michaelingp View Post
I suppose we might think of the resistor as a hard-to-replace fuse. The aggravating part is I'm quite capable of replacing a resistor if I only knew the specs, but as car_ramrod's picture shows, the resistor completely disappeared. I also agree the engineering should have prevented catastrophic damage from such a common mistake.
Are you sure it was a resistor and not a diode? If Hitec did put a diode in for reverse voltage protection...and a fuse was not available to blow... the diode would vaporize with wrong polarity. And.... if that is the case, it has nothing to do with the unit not functioning correctly.

If that theory is correct, Hitec is saving y'all from going into the rig thinking you see what is damaged and that part replacement will solve the problems.
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Old Apr 29, 2013, 09:30 PM
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Yes definitely a resistor thats what the r in front of the #stands for. Diodes say diode or d in front of the #
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Old Apr 29, 2013, 09:35 PM
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Originally Posted by AA5BY View Post
Are you sure it was a resistor and not a diode? If Hitec did put a diode in for reverse voltage protection...and a fuse was not available to blow... the diode would vaporize with wrong polarity. And.... if that is the case, it has nothing to do with the unit not functioning correctly.

If that theory is correct, Hitec is saving y'all from going into the rig thinking you see what is damaged and that part replacement will solve the problems.
The only evidence that it's a resistor is the "R29" printed on the circuit board. There's no doubt there could be more damage, but if I knew the value of the resistor, I'd be willing to give it a try. After all, it's already broken.

If it wasn't clear, this charger has a 22 amp AC power supply built into it, as well as the typical clamps to hook up to 12V DC (like a car battery). What happened is I was connecting it to the car battery and I got the red and black reversed for a second. There was a puff of smoke, but I instantly realized my mistake, and I connected the leads correctly and the charger worked fine. I thought I'd gotten lucky, but, when I got home, I found the charger no longer works on AC. It still works fine from a car battery or a 12 volt power supply.

If I hadn't seen this thread, I was just going to buy a stand-alone power supply for it. That wouldn't be quite as convenient, but I could get a better power supply that I could use for other stuff for not much more than it would cost to have Hitec fix the charger.
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Old Apr 29, 2013, 11:28 PM
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I glanced at the picture but did not see where and what. Yes, an R # would no doubt be a resistor.and you could be right, that the resistor gone, eliminates the path from the internal power supply and it is possible that is all that is out.

Where is the board? What has to be taken apart to see it?
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Old Apr 30, 2013, 08:02 AM
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You have a 1 year warranty. Are you past 1 year? Even then Hitec has been very good about fixing things for me. I sent them my TX to be fixed past the 1 year warranty point and they fixed it for free and sent it right back to me. When it was still in warranty I broke a switch and they replaced that for free when it was clearly my fault for breaking it.

But yes sadly you will have to part with it for a bit while it gets repaired.
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Old Apr 30, 2013, 09:26 AM
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Originally Posted by AA5BY View Post
I glanced at the picture but did not see where and what. Yes, an R # would no doubt be a resistor.and you could be right, that the resistor gone, eliminates the path from the internal power supply and it is possible that is all that is out.

Where is the board? What has to be taken apart to see it?
The board is pretty easy to get to, just a dozen screws on the side panels and the top lifts up, and you disconnect some ribbon cables.

I was thinking: What about using a 10 watt variable resistor to figure out the size of the actual resistor? Connect it to the wire stubs, set it at infinity, then gradually lower the resistance until the thing works. Measure the resistance at that point to figure out what the actual resistor should be. My guess, from the size, is the actual resistor was probably not much more than 1 watt. As I said, it's already broken, so not too much risk if you're careful. Anybody think that would work? I'm thinking since we now know the DC and AC power supplies are connected, you could probably just monitor the voltage produced at the DC connector.
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Old Apr 30, 2013, 03:16 PM
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If u look at the picture u see a red and black wire and a small black round thing. You will see the r29 there is a part thats burnt thats the resistor all u should have to to is take out the screws and you should be able to see it with out disconnecting. Anything if u could do that and get a good picture of the color rings on the resistor and list them in order that would be awesome
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Old Apr 30, 2013, 03:44 PM
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It seems to me that the resistance had to be less than 1000 ohms (and probably less than 500). Otherwise, there's no way that a 12 volt battery could vaporize it in a split second. Can someone who knows something about electronics confirm this?
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Old May 10, 2013, 09:59 PM
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I also have R29 "blown" in my unit and Hitec refused to tell me the value and I am an electronics engineer. Judging by the size of the leads it would be a high current/high wattage resistor probably around 100ohms and maybe 5/10 watt.

Verification by someone with a serviceable unit would be great and if you don't know how to read resistor colour codes just a quick "in focus" photo as above from your phone would be great and much appreciated.

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