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Broken DX7 switch - shall I try to fix it?

Old 10-21-2011, 11:45 PM
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mclarkson
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Default Broken DX7 switch - shall I try to fix it?

Somehow, my FLAP switch has broken on my DX7. No drops or bangs that I recall; I went to fly one day and it was just missing.

I contacted Horizon and talked to my LHS - they both say I need to send the Tx in to Horizon for repair. The thought of being grounded for weeks while I wait for my Tx is nigh on intolerable.

I know I can find a replacement switch somewhere, surely. How risky/dangerous/difficult/tricky is it to pull this Tx apart and replace a switch? I am not at all an engineer, but I've soldered a little bit (battery and ESC connectors, etc.)

I certainly don't want to make things worse, but I also don't want to be without my radio for weeks if I can help it (I fly every day.)
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Old 10-21-2011, 11:56 PM
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rcers
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This is why you need a backup TX. I have never done the repair and if it were me I would send it in. I don't suspect it is rocket science however.

Mike
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Old 10-22-2011, 12:36 AM
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DX7 flap switch replacement?

Broken Gear switch on DX7


Google is your friend.
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Old 10-22-2011, 12:43 AM
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If you have basic soldering equipment and skills it's not rocket science. A digital camera is your friend - take progressive pictures as you dissassemble, will help solve the CRS Syndrome when you put it back together.

Broke most of the top switches off my old Futaba 9C 'way back - fixed it easy enough.
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Old 10-22-2011, 02:36 AM
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kyleservicetech
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Originally Posted by mclarkson View Post
Somehow, my FLAP switch has broken on my DX7. No drops or bangs that I recall; I went to fly one day and it was just missing.

I contacted Horizon and talked to my LHS - they both say I need to send the Tx in to Horizon for repair. The thought of being grounded for weeks while I wait for my Tx is nigh on intolerable.

I know I can find a replacement switch somewhere, surely. How risky/dangerous/difficult/tricky is it to pull this Tx apart and replace a switch? I am not at all an engineer, but I've soldered a little bit (battery and ESC connectors, etc.)

I certainly don't want to make things worse, but I also don't want to be without my radio for weeks if I can help it (I fly every day.)
If your abilities for soldering are fairly decent, fixing this switch is not a difficult job.

First, open the battery compartment and remove the transmitter battery from the unit. Find an old deep dish metal baking pan, and line it with a old towel or similar. (So nothing can roll off and disappear!) Then with a good quality phillips screwdriver, locate the six screws in the back of the transmitter, and remove them. Place those six screws in a secure place.

The back of the transmitter can now be removed. Note that the battery wires will be holding the transmitter and its back cover together, don't strain these wires. Don't worry, nothing inside the transmitter will fall out. (I've got two DX7 transmitters, and have had both of them open at one time or another for switch modifications.)

Now, for removing the busted switch, pick up a cheap pair of needle nose pliars, and grind down the points so they will fit into the slots for the switch's nut. Then spin the nut off, and remove the switch and its attached wires. Use a small 10-20 watt soldering iron, and remove the wires from the switch. No this is not the time to use your 100 watt soldering iron designed for making glass window designs!

Pick up a dual pole dual throw switch from a reputable dealer that will fit into your transmitter. Solder the three wires of the transmitter switch to the corresponding three terminals of the DPDT switch. And parallel connect the two poles of that switch. Note that this flap switch is a three position switch, with a center off position. Radio Shack may not stock it.

Digikey does have a switch whose switch body measures 0.32 by 0.36 inches. Make certain this switch will fit inside your transmitter.
http://search.digikey.com/us/en/prod...2458-ND/378927 Digikey sells to anyone with a credit card. They do have next day air for $$$$.

It's a common trick to use parallel connections on these switches for extra reliability. The problem with this stuff is these switches are operating at very low currents and very low voltages. Even a speck of dust on the switch contacts could result in no connection.

And, NO, don't leave the switch as is. These switches use spring pressure on their contacts. And that spring is located inside the switch handle, the part that is busted off. That would leave that switch with little or no pressure on the internal contacts. Just moving the transmitter back and forth could result in changing the status of that switch.

Hope that helps.

Last edited by kyleservicetech; 10-22-2011 at 04:42 AM.
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Old 10-22-2011, 08:26 PM
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mclarkson
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Thanks for the advice. I've found a few switches on line, like this one and this one.

Last edited by mclarkson; 10-22-2011 at 10:26 PM. Reason: Corrected links
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Old 10-22-2011, 10:15 PM
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kyleservicetech
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Originally Posted by mclarkson View Post
Thanks for the advice. I've found a few switches on line, like this one and this one.
That first JR switch should do it. Looks like a single pole double throw, rather than double pole double throw. So you'd loose redundant contacts, but odds of the switch failing are rather low.

Before retiring, the switches we used might be operated once or twice a year. That is where you can get into trouble in low voltage, low current applications, unless the internal switch contacts are gold plated.

Some of our critical applications used four contacts in parallel for reliability. And we'd still have a switch failure now and then.

Last edited by kyleservicetech; 10-23-2011 at 01:17 AM.
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Old 10-22-2011, 10:26 PM
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I posted the wrong link there. The second one was the wrong switch altogether.
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Old 09-30-2013, 10:42 PM
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Holy procrastination, Batman! I finally worked up the nerve to pull my Tx apart and attempt this repair myself. Horizon Hobby was willing to fix it - if I sent it in - but I was unwilling to live without my Tx for several weeks.

I was also too scared to try and fix it myself. But finally, after nearly a year of dithering, I pulled the DX7 apart yesterday and replaced the broken switch with a $3 item from the local Radio Shack - a #275-0325 Single-pole / Double-throw toggle switch.



So far, it's working perfectly - although do I miss the extra-long original switch.
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Old 09-30-2013, 11:01 PM
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Now that you found how simple it really is...

You can look around for a switch that has the lever you want.
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Old 09-30-2013, 11:15 PM
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Everything's simple, after you know how to do it.

I found a few online but they were $10 or more and out-of-stock, to boot.
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Old 10-01-2013, 02:39 PM
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Heck, all it needed was a chunk of something with the right threads in the end.

Probably could have found the lever with a metal detector at the field!
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