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  1. #1
    Moderator CGRetired's Avatar
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    Field charger use on DX7

    Does the DX7 utilize a blocking diode (reverse polatity protection)?

    I have a Sirius field charger for NiCd and NiMH batteries and it won't work unless the diode, if it has one, is shorted out. Does this void the warranty for the DX7? If it does then we are pretty much stuck with the wall mounted 50 ma charger and would be limited to battery life duration flights with the DX7 for that day's flying unless we carry a spare battery.

    DS.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  2. #2

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    RE: Field charger use on DX7

    G'day Mate,
    I would say definately "yes" it is made by JR so it would have a diode. dunno about the warranty though.
    I just sent you a pm about this radio, & if & when I get one I will be taking the diode out of the circuit the same as I have done with my X378, for the same reason as you.
    Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee,
    Allan.

  3. #3
    dsnyder's Avatar
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    RE: Field charger use on DX7

    No, it does not have a diode in the charge circuit. All JR and Spektrum air systems in the US do not use a diode in the charge circuit. Also Spektrum is not "made by JR". Some parts are sourced from JR, but JR is not the manufacturer of the Spektrum systems. They are 2 different companies. Make sure you have the polarity correct (center pin negative) on your charger. Reverse polarity damage is not covered under warranty.
    Danny Snyder
    Horizon Hobby / Team JR

  4. #4

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    RE: Field charger use on DX7

    G'day Danny,
    I was wrong, I stand corrected.
    My JR Radios had a diode in the TX charge circuit here in Australia.
    Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee,
    Allan.

  5. #5
    Moderator CGRetired's Avatar
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    RE: Field charger use on DX7

    Danny:

    So you are saying that there is no reverse protection diode in the US distributed Spektrum DX7 transmitters, correct? Also, by this, I imply that I can use my Sirius field charger provided I observe that the center pole is opposite polarity from my Airtronics, that is the center pin is negative vs. positive which is the way Airtronics and Futaba are. Correct?

    I fully understand that damage caused by accidental reverse polarity would not be covered.

    It seems that the safest method of charging this in the field is to charge it with the battery removed. Does it have a non-volatile memory for model settings? (I would assume so, there isn't much on the market now that has volatile memory for such important functions). Reason I ask, of course, in case someone does not understand the question, if I remove the battery for an hour of charging, the transmitter retains all model memory information... please correct me if I am wrong.

    DS.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  6. #6
    Mac_Man_UK's Avatar
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    RE: Field charger use on DX7

    alan, thats one of the few differences between the US sets and ROTW (rest of the world) sets manufactured by JR. The ROTW ones invariably have the protection diode fitted and the US ones will have a strap bypassing the diode (if fitted).

    I know the DX7 isn't a "JR" set per se, but as the body and cpu pcb etc are manufactured by JR on behalf of Horizon/Spektrum, I would imagine that the usual build standards/variants apply. Mind you, I could be wrong on this as the DX7 (before it is a true DX7) is shipped only to the USA.

    UK JR Tech.

  7. #7

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    RE: Field charger use on DX7

    G'day Mac Man,
    The DX7 is available now in Australia, I have a couple of X370 JR's & I had no problem bypassing the guiding diode, in them.
    I'm sure most of the DX7 is manufactured by JR, too many similarities with JR sets.
    Maybe the circuity is Spectrum design, anyway they sure seem like the way to go.
    I assume they can be purchased in Mode 1 or Mode 2.
    Here in Aus, mode 1 is the most common, but mode 2 is used as well, of course.
    Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee,
    Allan.

  8. #8
    dsnyder's Avatar
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    RE: Field charger use on DX7

    There is no diode in the charge circuit, there is a fuse, but no diode. The polarity is center pin negative, which is the same for all Spektrum and JR equipment.

    The DX7 is not manufactured by JR. JR does supply some parts, but they are not the manufacturer of the system. Spektrum is the manufacturer.
    Danny Snyder
    Horizon Hobby / Team JR

  9. #9

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    RE: Field charger use on DX7

    Danny

    This may have been answered before and I apologize if it has but why in the world have the charge plugs reversed from the other manufactures? So us old guys will have a better chance of screwing up the battery by using the wrong charger?

    Also, why are they using a 50 mah charger for a 1,500 mah battery, makes no sense. Why didn't they use a 100 mah as ststed in the DX-7 manuel?

    Thanks

    Larry

  10. #10
    dsnyder's Avatar
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    RE: Field charger use on DX7

    Some manufacturers set their eqipment up one way, others chose another. There are a few brands that use center pin negative and a few that use center pin positive.

    Here again, this is simply a choice that was made.
    Danny Snyder
    Horizon Hobby / Team JR

  11. #11

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    RE: Field charger use on DX7

    Dan,

    Thanks for your reply. If must add that I have been flying the DX-6 and now my new DX-7 with no glitches or any indications of control problems. Today I was standing within 10 feet of a guy on channel 48 and another guy with a DX-7 and no one had any issues. Keep up the great development work for we all benefit from these modern electronics gizmos.

    Larry

  12. #12
    dsnyder's Avatar
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    RE: Field charger use on DX7

    Great to hear!
    Danny Snyder
    Horizon Hobby / Team JR

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    RE: Field charger use on DX7

    Dan,

    I have the DX7 Transmitter. I tried to charge it with my Sirius Peak Charger. It blew the fuse. I did use the reverse polarity connector. If there is no diode then why would the fuse blow.

    Thanks, Arno

  14. #14
    dsnyder's Avatar
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    RE: Field charger use on DX7

    When you say "reverse polarity", did you use a connector with center pin negative? If not, that is reverse polarity damage. If you did have polarity correct, any number of things could have caused the fuse to blow, static electricity discharge when you plugged the connector in, a damaged/worn/incorrect charge plug, too high of a charge rate (I recommend 1 amp or under), or any number of other possibilities.
    Danny Snyder
    Horizon Hobby / Team JR

  15. #15

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    RE: Field charger use on DX7

    I have a SPEkTRUM DX7, mode 2, heli, purchased locally from a dealer supplied by the authorised distributor in Australia.

    Firstly, thanks to Horizon for bringing us SPEkTRUM. Although just commencing the transition, adopting DSM2 has been the best move I've EVER made in RC. Other than serving as buddy boxes or retention of my now synthesised module driven venerable X-388S for legacy compatibility purposes when required, I doubt I'll have any other PPM/PCM kit left in my hanger within 18 months time. The change-over will cost me less than a single idiot or interference driven shootdown.

    Because of the 'conservative' charge rate of the set included charger, I regularly charge my DX7 TX NiMh via its charge port using an external charger (SJ Propo PlatinumEX) using a JR orientated polarity charge lead. (Hyperion/Hobbico/CY, etc). It charges without issue, and importantly for NiMh, will peak detect (uses zero delta V) and cut-off or fallback to trickle depending upon how the preference is set. The zero peak delta sensitivity can also be adjusted. For basis of comparison, I similarly charge my NiCADed X-388S ('97), XF631 ('04), MAX66ADT (XP-662) X3 ('06), Quattro ('05), venerable MAX44 ('96) all without issue via their TX charge ports at rates > C/10 using this charger. Never blown a fuse. This charger does have reverse polarity detection, though TMK it's never been tested on the JR TXs as Cap'n Crosscheck here tends to be kinda' extra careful about that sort of thing.

    Worthy of mention, Danny has oftimes said here that 1.2A is JR's recommended maximimum charge rate via the TX charge port. So that said, I don't charge my 1500mAh NiMh at 1C when in the TX because of that and the fact that NiMh cells get notably hotter than NiCads when being fast or rapid charged. This is discernible in the DX7 case even at C/2 or C/3. Playing it safe (NiMh overcharge) or supply oversight......I am surprised though that the unit wasn't supplied with a wall wart capable of C/10 output for the TX battery.

    IME, apart from seldom being flattened to the extent that a 1C full capacity charge is necessitated timewise, I am conservative for all the obvious common sense reasons when charging via the TX charge port. If I have the time, I charge at C/10. If under pressure of time, usually C5, C/3 or C/2. Topping up seldom takes longer than 20 minutes. I have charged at 1.2A. All without incident. Ordinarily however, if I want to cycle or charge the TX NiMh (or NiCads) at anything higher than 1A, I remove the batteries and charge externally where they are surrounded by air and resting on a heatsink of sorts so the generated heat (esp. from NiMh) is more readily dissipated.


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    RE: Field charger use on DX7

    Dan, Thanks for the fast reply. Yes the center pin is negative. What I didn't make clear was that I used the same reverse polarity connector on my Serius as I use to charge my JR 10X. I'm an old Electrical/Electronics guy so I understand that fuses can blow from a surge. I did install a new fuse and all is okay (no damage) but I hesitate to try the Serius again at least until I could get more info on the transmitter.

    I have been pulling the battery out and charging it with the same Serius and no problem. Also I am flying with the spektrum, Love it and especially enjoy the digital throttle trim.

    I'm open to your suggestion as to trying it again. Do you know if others are using the Serius Pro to charge the transmitter:

    Arno


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    RE: Field charger use on DX7

    Dan,

    I also meant to tell you that my Serius max output is 1 amp and it was set on that when I plugged it in. I have 3 settings, 250 ma, 500 ma and 1000 ma.

    Arno

  18. #18

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    RE: Field charger use on DX7

    Dan,

    Update! I decided to go ahead and take the chance. I reduced the ouput of my Sirius to 500 ma and plugged it into the DX7. This time the green charge light lit and it is charging. I am really glad because pulling out the battery for each fast charge is both hard on the battery wires and connector.

    I had decided if it gave me more trouble, I would install another jack that would cut off the circuit to the transmitter when I plugged in the charger. That might have canceled my warrenty but I have found that using the Sirius charger really extends the life of NICD's and I hope NIMH's.

    I really appreciate these forums. It gets pretty lonely when one has a problem.


  19. #19

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    RE: Field charger use on DX7

    Problem not resolved! After the second Sirius charge of the Spektrum transmitter I turned it on an it worked fine. I went to the field, turned it on and it blew the fuse. So now I know it is not the Sirius coausing the problem.

    I think it may be NIMH Battery causing a high current suge. Two things I intend to try:

    1. Install a slow blow 3 amp fuse

    2. Install a NICD battery and see if it the quick 3 amp fuse holds.

    Arno

  20. #20
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    RE: Field charger use on DX7

    I have just the charger that came with the DX7-- for charging the TX
    I can fly all day long on one charge.
    why the need for fast charging it ?
    After an overnight charge (typical)-The tx reads 11.5 -
    that will (and does)fly it for the entire day. Are you guys just playing around with chargers are do you actually, find that the batter does not fly for 8 hours ?
    did you initially charge with with the wall charger? for acouple of cycles?
    I do have a bunch of fast charging equipment for NiCad/Ni Mh and A123 cells but so far never seen a need to "fast charge " THIS tx.
    My rx are all DX2 types.
    The JR radios 10 series --x/6102 / 9303 etc., all came with batteries which ran from 2 hrs or more but this DX7 -on DX2 mode flies the entire day for me .
    I can't see why a fast charge is needed.
    Libby is still watching you

  21. #21

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    RE: Field charger use on DX7

    Well first I have a couple of reasons to use the Sirius Peak charger. I cannot plan my field trips ahead any more so I have a self containd box with battery, meters and a Sirius charger. Anytime I am free to stop at the field I just put the transmetter and receiver on charge for about 15 minutes and I'm flying.

    Also I have proven that using the Sirius really extends the life of the batteries since they never overcharge as with a wall charger, causing loss of battery life.

    Yes, i always cycle new batteries. However in this case since the manual said the charger was 110 ma. I believe the charge cycles of 10 hours did not do the job. Of course I know now the charger is only 50 ma.

    I also am an old timer and could never trust a battery for flying without peaking it. I also had problems with NIMH batteries failing in the past and swore I would never use them again. Perhaps they were faulty when I purchased them. After using the transmitter for awhile I may learn to trust it more.

    At any rate it should be possible to quick charge the battery in the Spektrum without blowing the fuse. If not then the circuit is underfused or there is a problem with the charge circuit. As said previously I think the battery surge may be the cause. After the battery is cycled enough maybe the problem will go away.

    Dick I appreciate your comments but since you are using a 50 ma charger, your plane may be at risk unless you are charging for 22 or more hours.

    Arno

  22. #22

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    RE: Field charger use on DX7

    ORIGINAL: dick Hanson
    I have just the charger that came with the DX7-- for charging the TX
    I can fly all day long on one charge.

    After an overnight charge (typical)-The tx reads 11.5 -
    The charger which came supplied with the DX7 has just 50mA output for the TX. Using the conventional math, ie: capacity / rate x 1.4, it takes 42 hours to fully charge the supplied 1500mAh TX NiMh. According to my reckoning, assuming a fully discharged battery, that's just 6 hours short of two days continuous charging using the supplied wall wart, not overnight.

    why the need for fast charging it ?
    Flying continuously hour after hour after hour with consecutive students whilst professionally instructing RC, I can assure you that whilst it's a welcome improvement over a 600 or 800mAh NiCad, the supplied 1500mAh NiMh the battery doesn't last literally "all day", and certainly often isn't recharged to full capacity "overnight" with the supplied 50mA output charger. Ordinarily, a "fast" charge isn't required in the conventional sense of the term, but a charge rate higher than C/30 is. If I have the luxury of overnight, charging at C/5 is fine ...and preferred. Charging at C/30 is fine for a top up, but rather than leave NiMh on at even that rate when they're fully charged, I prefer the zero Delta V Peak detection and cut-out facility offered by my external charger, the audible alarm it sounds when the charge is completed, and the information supplied by it in terms of battery condition (capacity and charge) and time taken to achieve it.

    Naturally, a form charge rate was used for the first few cycles. In my own case, I form charged at C/10 x t determined by zero delta V peak detect.


  23. #23

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    RE: Field charger use on DX7

    Really good info sigrun. I instructed for years and purchased the Sirius in 1999 for the same reasons. Do you have any comments about the fuse blowing? I want to let everyone know that since my last fuse replacement I have charged the Spektrum 3 times and have been constantly turning it off and on without a problem.

    Looks like I am correct about the battery surge. (knock on wood)

    Arno

  24. #24
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    RE: Field charger use on DX7

    do as you wish - however - my overnite charges are NOT starting from a dead battery and therefor the full charge is as stated .
    once again - from a full charge a days worth of flying is available
    also at 50 ma the charger is well below 1/10C -so leave it on a couple of days so what? do you fly everyday ?

    sigrun -do you actually run students for 8 hours in a day ?
    really?

    you have my condolences -
    for the typical user - the 50 ma charger is just fine.
    Libby is still watching you

  25. #25

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    RE: Field charger use on DX7

    Hi arno

    In short, if you'rer blowing the DX7's fuse, don't replace it with a higher rated fuse or you'll likely damage your TX. Determine the cause, which is most probably your 8 year old charger. Nothing lasts forever, and sounds to me that your charger is malfunctioning if you're setting a reasonable charge rate and it's consistantly blowing the fuse.

    We shouldn't really be discussing stuff in here Arno as it's the manufacturer's oficial forum, even if Danny is lenient about third party comment which I'm sure we appreciate. If you want to chat about it some more, we can take it to PM.

    Cheers,

    sigrun


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