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Radio question

Old 01-16-2017, 01:49 PM
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Thoken
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I have been out of the sport for awhile now and i am wanting to get back in it. I have a Spektrum DX7S radio that i went to go buy batteries for it and they are not finding them being offered anymore? Does anyone have any suggestions or have you run across this before? They discontinued the radio this year is what i heard.
2000mAh 4.8V NIMH

I just received a phone call as i was typing this and they are recommending this battery pack as a replacement
[h=1]2000mAh Transmitter Battery: DX9, DX7S, DX8 (SPMB2000LITX)[/h]

yes it is a 2000mAh but is says 7.4V and it looks like it is a 2 batteries pack rather than like my old pack had 4 batteries in the pack.
Will it fit?
Old 01-16-2017, 04:34 PM
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Hydro Junkie
 
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I would send your radio gear to Radio South and have them check it over as well as replace the batteries. Then you'll know you're using a good system. Something that isn't common knowledge is that circuit boards can go bad over time. They can and do corrode, solder can magnetize and other parts can fail.
Old 01-16-2017, 05:34 PM
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Agreed, if it's been shelved for awhile, then it should be checked.

The battery only has 2 cells, becase 1 lipo cell has a nominal voltage of 3.7, fully charged a 4.2. So 2 cells is 7.4 nominal/8.4 charged, unlik 1.2/1.45 volts per celll on a nimh. Personnaly, I recommend a eneloop pack for you transmitter. It is a low self discharge cell, will last long, so the only real advantage that the lipo has is weight, but it's only a transmitter. I don't like lipos in my transmitter, but that's just me.

These guys have a pre soldered eneloop pack designed for a dx7s: http://www.batteriesamerica.com/newpage8.htm

Hubert
Old 01-17-2017, 07:13 AM
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Originally Posted by krokodyl View Post
Agreed, if it's been shelved for awhile, then it should be checked.

The battery only has 2 cells, becase 1 lipo cell has a nominal voltage of 3.7, fully charged a 4.2. So 2 cells is 7.4 nominal/8.4 charged, unlik 1.2/1.45 volts per celll on a nimh. Personnaly, I recommend a eneloop pack for you transmitter. It is a low self discharge cell, will last long, so the only real advantage that the lipo has is weight, but it's only a transmitter. I don't like lipos in my transmitter, but that's just me.

These guys have a pre soldered eneloop pack designed for a dx7s: http://www.batteriesamerica.com/newpage8.htm

Hubert

Good advice krokodyl, agree whole heartedly.
Old 01-18-2017, 07:47 AM
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Hi!
??? I would solder four (if that is what the radio had ) NiMh cells/batteries together so you get 4,8V.
Lipos in a transmitter is not what I would use as the fire hazard is to high.
Pictures below show two sets of receiver packs, one 4,8V 850mAh and one 6V 850mAh.

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Old 01-18-2017, 10:45 AM
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This looks like a good fit, you'd need to swap the connector from your old batter with the standard servo connector that it comes with:

https://hobbyking.com/en_us/turnigy-...8v-nimh-1.html
Old 01-18-2017, 12:11 PM
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Why would you send it anywhere but back to Horizon for a check up? They are the authorized service center and will do the best and most economical job.
Old 01-18-2017, 04:11 PM
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EloyM
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Solder will magnetize??????????????????
Old 01-18-2017, 07:07 PM
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Yes, it will. Any time electricity is sent though a wire, solder joint or anything else, it creates a magnetic field. Over time, most metals will become magnetized. Silver solder is very susceptible to this and will, in a very short time, stop conducting electricity. Anything made with ferrous metals will do the same, again in a very short time. Copper and aluminum are the most resistant but, like everything else, resistance is not proof against something
Old 01-18-2017, 08:10 PM
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I would put an enloop nimh pack in it from a reputable source such as electrodynamics.. I would not put a lithium battery in it. Depending on the version of dx7 it could shorten the life of the transmitter deck inside. I wouldn't send it in if it works properly.. more likely to cause more problems by having it banged around in shipping both ways plus having somebody crack it open.. A birdie told me that the older dx7 may have a bit more output power than than the current issue spektrum transmitters.. I know my old dx7 will outrange my dx18 by 2x the distance.
Old 01-19-2017, 05:32 AM
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Is this the original DX7S in the JR case? If so, I think they were NiCad batteries. SR batteries can put a pack together for anything with the correct connectors. There are still a few of these radios flying at our field and seem to work fine. They have the older, more to difficult programming but if you are not doing anything complicated, these were great radios. But as someone suggested, would not hurt to send back to Horizon Hobby to get checked out. They have always been reasonable cost wise for me

bob
Old 01-19-2017, 07:32 AM
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Hi!
Why send it back if the radio is working?? I supposed it was just a battery change!? In that case solder a pack together yourself! -Could not be easier.
I have that transmitter too (Spektrum DX 7S) contains 8 NiMh cells.
Old 01-19-2017, 06:39 PM
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Originally Posted by jaka View Post
Hi!
Why send it back if the radio is working?? I supposed it was just a battery change!? In that case solder a pack together yourself! -Could not be easier.
I have that transmitter too (Spektrum DX 7S) contains 8 NiMh cells.
Because, as stated above, parts can go bad. Would you trust your new plane to a radio that may have corroded gimbals or battery leads that's been sitting on the shelf for several years? Sending it in and getting it checked out means that these possibilities are removed
Old 01-19-2017, 08:51 PM
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A. J. Clark
 
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I have the DX7s. When my battery went bad I didn't want to use a lipo . I put a Hobbico hydrimax 2000 mah in. Took the connector from the original battery and soldered it to the new battery .
Old 01-20-2017, 07:55 AM
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Hi!
??? Just take it apart yourself! It's not too difficult .
Old 01-20-2017, 02:35 PM
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Thank you all for your help.
Old 01-20-2017, 04:40 PM
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Originally Posted by jaka View Post
Hi!
??? Just take it apart yourself! It's not too difficult .
Trust me, I know electronics and, you're right, taking it apart isn't hard. What is hard is to get the US FCC license to be able to do so legally. To change anything inside a transmitter, without the proper training and licensing, is asking for major legal problems.
Old 01-22-2017, 06:24 AM
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Rodney
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As long as you do not tinker with the RF section (and most problems are NOT in that section) there are no legal problems. All the programming, stick functions, charging, buddy box stuff etc. are fair game to repair or play with.
Old 01-22-2017, 01:41 PM
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Play inside your transmitter if you want but, without a manufacturer's parts list and schematics in hand, I'm not touching mine. I'd rather send mine in and let someone that knows them and has the literature check it over. When you think about it, would you rather work on your own flat screen TV or let someone that knows them do it?
Old 01-29-2017, 01:47 PM
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Hi!
Changing batteries in a transmitter isn't rocket science !
Old 01-30-2017, 08:35 PM
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Originally Posted by jaka View Post
Hi!
Changing batteries in a transmitter isn't rocket science !
No it's not, but I'm not just talking changing batteries here. I'm talking a complete check up on everything, batteries are just a small portion
Old 02-03-2017, 07:49 AM
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Originally Posted by Hydro Junkie View Post
Yes, it will. Any time electricity is sent though a wire, solder joint or anything else, it creates a magnetic field. Over time, most metals will become magnetized. Silver solder is very susceptible to this and will, in a very short time, stop conducting electricity. Anything made with ferrous metals will do the same, again in a very short time. Copper and aluminum are the most resistant but, like everything else, resistance is not proof against something
Standard solder for electronics work is lead/tin. Soldering battery leads AND radio circuits with it WILL NOT cause magnetism problems. In all the electronics assembly and work I've done including digital circuits, never had a problem with it. However, I've had problems with a magnetized screwdriver near radio circuits. I've brazed with silver solder, definitely not suitable for hand assembled / repaired electronics.
Old 02-03-2017, 03:28 PM
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The problem with silver is not magnetism but migration. Silver, over time can migrate enough to cause problems with printed circuits where the traces are very close together. I've never had a problem with magnetism being caused by soldering and that is after some 40 years of working with electronics and instrumentation on most all types of electronics.
Old 02-03-2017, 07:26 PM
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Just got to thinking, the EU and other countries have gone to lead free solder. Here in US, it is still permitted, although in manufacturing there is less and less. Hence, am less familiar with the newer tin solder with silver alloys. When one said silver solder, usually referred to non-electronics work, and those rods were getting into brazing temperatures.

I've been soldering for the past 48 years, started with point-to-point tube (valve) circuits, then discrete component and low scale integrated circuits. Never had a problem with 60/40 and similar standard tin/lead solder. Still have plenty of it, so for radio and electronics repairs suit me fine.

Haven't used any of the lead free (electronic assembly) solders yet. Times have changed with the green movement. Loved using the Weller temperature control stations with my employer 30 years ago. At home, still using my Graymark 40 Watt soldering iron from high school, albeit changed out the power cord 30 years ago. Never invested in a sophisticated soldering station for home use, the old 40 Watt and newer Radio Shack 30 Watt were hot enough. Then, put together a Charlie's R/C Cannon 810 4 channel mini R/C system kit. Only thing assembled was the transmitter section circuit on the PC board. At least in US, as long as one (unlicensed that is) doesn't dink with the RF (radio frequency) section, should be OK.

Gone are the 40 Watt $1.50 Graymark soldering irons of the late 1960's. (Still got one with screw on wooden handle albeit with a new cord replaced 30 years ago.) Did some work recently on an FM broadcast receiver kit that included a few surface mount components like an IC and several resistors. That was a challenge to not bridge solder joints with such tight spacing. With a schematic written in Chinese, was a challenge to decipher.

As in all things, if one doesn't have the knack for working with electrical circuits, best let someone else do it.

Last edited by GallopingGhostler; 02-03-2017 at 07:31 PM.

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