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Did I fry my transmitter?

Old 05-17-2015, 06:28 PM
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AllModesR/C
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Default Did I fry my transmitter?

I have a JR XP642 72mhz transmitter with a regular Nicad battery. I plugged a Futaba brand charger into and and now it won't even turn on. The charger got very hot. Any ideas?
Old 05-17-2015, 09:01 PM
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JohnBuckner
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No very unlikely that you fried anything, what you did do was burn out the fuse. Yup good old fashioned glass fuse easy to replace on the simpler radios like the 642 but a bit more difficult on the more complex radios like the 10 channel stuff.

Open the case and you will find it.

John
Old 05-17-2015, 09:15 PM
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Oh yes forgot to mention. For whatever reason JR choose to wire their tx charge jacks reverse polarity of all the others at the time and not sure about Spectrum since I do not speak Spectrum

Their servos are the same as all modern systems it is only the reversed tx charge jack and their chargers. If you like you can simply reverse the wires on the wall chargers however do not ever use it on another brand tx.

John
Old 05-18-2015, 02:40 AM
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Rodney
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If the charger got very hot, you had more than a burned out fuse problem. A blown fuse would not cause the charger to get hot. More probably you got a short circuit somewhere (bare wires touching, frayed cable, ???).
Old 05-18-2015, 03:45 AM
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Rodney is correct the fuse would have opened and at that point no current flow. No flow the charger doesn't heat up.
i was given a Futaba 8 once where a JR charger was hooked to it if you looked at the board and followed the conductor you could plainly see where it burned.
i recommend opening up your transmitter and following your nose. You should smell where the magic smoke came from. You know the magic smoke once it's out can't be put back and whatever doesn't work.
Perhaps it's an excuse to get a new 2.4 transmitter
Old 05-18-2015, 04:21 AM
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I opened up the transmitter and could not find the fuse anywhere.
Old 05-18-2015, 05:01 AM
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JohnBuckner
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Find the fuse and replace it. Its there!

John
Old 05-18-2015, 06:57 AM
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All Day Dan
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You reverse charged the battery pack in the transmitter. It is possibly ruined. Try charging it with a Futaba charginger. It may regain some charge and the transmitter will start working again. The battery will defintely have to be replaced before you use it. I doubt if the fuse was effected. Dan.
Old 05-18-2015, 07:12 AM
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both jr and spectrum are reversed polarity. I would send it in for service to be on the safe side. I have never seen a fuse in my airtronics radios.
Old 05-18-2015, 07:49 AM
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JohnBuckner
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This is not an Airtronics it is a JR Yes there is a fuse and it did its job your battery pack is fine. If the charger was heated any shorting likely occur external of the transmitter typically at the plug wire juncture or at the wire where it enters the potted charger.

Find an replace the fuse! On your its likely behind the circuit board.

John
Old 05-18-2015, 07:52 AM
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Originally Posted by AllModesR/C View Post
I opened up the transmitter and could not find the fuse anywhere.
All the transmitters I've had - regardless of brand - in which there was a fuse had it right by the socket that the charge cord plugged into. Some were soldered in line.

The fuse looks like a small, glass tube with a silver band on each end. Inside there is a fine wire or strip of metal connecting the two metal ends. If it's fried, you will see that it is broken. Could even be some black residue on the inside of the tube from when it went poof.

I've also found that chargers get warm when plugged into a wall socket, even if not charging anything. That's because there is electrical current running through the coils of the part that's plugged in.

If you look at how these things are constructed, you'll see that there are two wire wrappings around a soft iron core. There's the side which plugs into the wall and then the side which goes to your batteries. The input current turns the soft iron core into an electromagnet. The magnetic field creates an electrical current in the the output coil. The amount of current is determined by the amount of wire that is wound around the soft iron core.

Look up electromagnetic induction and you'll learn all you need to know about how these things work.
Old 05-18-2015, 08:24 AM
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Do335a, you just described a crude transformer. There is much more to a charger than that. There's always rectifier circuits, voltage regulators and current regulators.
As how much current comes out of a transformer, you really need to define turns ratios as well as understand Ohm's law and it's current to voltage relationships. If there are more coils on the output side of the transformer than the input side, you have higher voltage and lower current while less output coils results in lower voltage and higher current. Normally, the charger is designed around the transformer output voltage so that the voltage regulator circuit only has to maintain the voltage, not take the stress of increasing/decreasing as well as holding the voltage to some other figure
Old 05-18-2015, 12:09 PM
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Originally Posted by Hydro Junkie View Post
Do335a, you just described a crude transformer. There is much more to a charger than that. There's always rectifier circuits, voltage regulators and current regulators.
As how much current comes out of a transformer, you really need to define turns ratios as well as understand Ohm's law and it's current to voltage relationships. If there are more coils on the output side of the transformer than the input side, you have higher voltage and lower current while less output coils results in lower voltage and higher current. Normally, the charger is designed around the transformer output voltage so that the voltage regulator circuit only has to maintain the voltage, not take the stress of increasing/decreasing as well as holding the voltage to some other figure

Quie right.

All of which is totally useless in helping AllModesRC understand anything about locating the fuse in his TX or appreciating why the charger may get warm.

I'm certain he could not care less what colors the wires are for the connnections inside the box, as long as it works. Same for the charger.

And as far as those basic, manufacturer supplied RX chargers go, open one up to see how little there is inside, other than two wire coils wrapped around a soft iron core. A high zoot device with all sorts of possible adjustments for battery type, capacity, pack voltage and so on is an entirely different matter. However, that's not what the OP is talking about.
Old 05-18-2015, 01:58 PM
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http://www.amazon.com/JR-Transmitter.../dp/B000BMAJLC


Allmodes this is a no brainer, this is the fuse you need and there is no magic just an ordinary micro glass fuse. An no they may not be located near the jack. On the 642 its most likely under the circuit board and that may require removing three post screws. I have replaced many from the six hundred series as well as the four hundred series. I did on one occasion actually replaced one on my trusty old 10SX, don,t care to repeat that.

John

Tell Ya what Dude I'll bet three burned out glow plugs aginst a stale glazed donut that if you replace the fuse in (rest assured its there) your tranny that it t is fine but may not be able to say the same for your wall charger.
Old 05-18-2015, 04:37 PM
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I found the fuse and it was fine. So I tried plugging in a different battery pack in and the transmitter works! Making progress with the problem child of a plane I bought off of Craigslist. Tried firing up the Super Tigre 40 and it fired instantly. I noticed that JR radios have a different battery connection than my Hitec radios. I did make it fit though. I can not make the original JR battery fit my charger connector. Will have to look for an adapter.

Last edited by AllModesR/C; 05-18-2015 at 04:40 PM.
Old 05-20-2015, 04:52 AM
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Originally Posted by AllModesR/C View Post
I have a JR XP642 72mhz transmitter with a regular Nicad battery. I plugged a Futaba brand charger into and and now it won't even turn on. The charger got very hot. Any ideas?
All this to get to here; a dead battery. Now what will we do for fun? I know lets go find an whats the best 2 stoke oil thread. Glad it was something easy to fix, I like easy, good luck with the rest of the project.
Old 05-20-2015, 08:54 AM
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Originally Posted by AllModesR/C View Post
I plugged a Futaba brand charger into and and now it won't even turn on. The charger got very hot. Any ideas?
The reason the charger got so hot was due to connecting the charger that had the opposite polarity. When you charge a battery pack, you're forcing electrons into the negative end of the cells. By connecting a charger that is reversed, you're now feeding electrons into the positive end of the cells and pulling them from the negative. The current flow is greatly increased, due to lack of resistance from the cells, heating up the components inside the charger
Old 05-26-2015, 06:50 AM
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My Spektrum DX6i appears to have a diode in series with the charging jack. That's for reverse polarity protection.
I say that because, if I try to discharge the battery, the discharger doesn't draw any current from the battery, but it will charge (send current to) the battery.

Jack
Old 05-30-2015, 05:25 PM
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AllModesR/C
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Now I think I really did "fry" my transmitter. I go to turn it on and nothing happens. So I think maybe the battery is plugged in backwards so I revers the connection, turn it on, and a horrible burning smell comes out from inside. I shut it off and again reverse the battery polarity and nothing happens when I turn the switch on. Battery is 100% charged and the fuse inside the transmitter case is intact. Anyone have a JR XP642 transmitter you want to sell?

Last edited by AllModesR/C; 05-30-2015 at 05:38 PM.
Old 05-31-2015, 07:22 AM
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Can you open it and see if you can see what's burned? If you're anywhere near Ft Worth, TX, I might be able to fix it for you.

Jack
Old 05-31-2015, 08:02 AM
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AllModesR/C
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I opened it up and can't locate anything burned. Thank you for offering but I'm in Chicago. I am thinking of sending it to JR for repair. It's a really nice radio, would hate to toss it in the trash.
Old 05-31-2015, 09:04 AM
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Don't toss it, send it to me.
Old 05-31-2015, 09:53 AM
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AllModesR/C
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Does anyone know if this JR transmitter will work with my R600 receiver?

http://www.ebay.com/itm/JR-XP6102-RC...item1e9f451436
Old 05-31-2015, 09:05 PM
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Yes it will

Last edited by JohnBuckner; 05-31-2015 at 09:08 PM.
Old 06-28-2015, 08:33 AM
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Originally Posted by Jack_K View Post
Don't toss it, send it to me.
Jack I ended up getting a different JR TX from a gentleman on this forum. If the want the broken XP610 Paypal me $15 for shipping and it's yours.

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