DX7 died, and remains dead

[xJAEx]

I accidentally plugged in a 12v power supply to my DX7 that I use to power my Cellpro charger...and now my DX7 will not turn on at all. When I plug in the correct charger for the DX7 the light does not turn on to indicate it is charging. I was just using the TX so I know it was working about 30 minutes before I made this error.

Any ideas on what exactly may be wrong and is it something I can fix? If not, where can I take it to? Or where do I send it? I bought it from a private party so its not under any warranty that I am aware of.

P.s. I'm in the San Fernando Valley, 818 (So. Cal)

Thanks,

[Jermo]

There's a fuse inside you probably blew out. If you can't fix it you can sent it back to horizon hobby for repair. Personally I'd goto a local hobby shop for help. Replacing the fuse is a pretty easy thing to do for someone comfortable working on things.

[Hughes500Bob]

The DX-7 has positive polarity on the outside of the plug case and negative on the core .... which is opposite of almost any charger plug I have used. This is clearly noted in the manual and on the stock Tx /Rx charger. :dontknow Why they did it this way is a mystery to me!

For safeties sake .... never plug a power supply into anything without knowing polarity and mAh voltage output? The stock DX-7 charger does the Tx NiMH (edit) at 11.6V @ 50 mA and I here it will take 150 mA max.

Probably you just blew the fuse as Jermo pointed out. If not you will have to send it back to Spektrum (Horizon Hobby) for repairs.

[Jermo]

The batery pack in my DX7 is NiMH 1000mAh. I charged it the first several times at 100mAh. I've ramped up to 500mAh now. Eventually I'll be able to do up to 1A.

[Hughes500Bob]

Jermo ..... You might want to read this:
http://www.powerstream.com/NiMH.htm
before you kill that NiMH battery, or heat it up to the point of damaging your DX-7. Of course you can push it with the correct charger and temp sensor as stated in the article. I'd remove it from the DX-7 if I was going to push it! Respectfully,..... Bob!

Highlights of article specific to this thread:

The coulometric charging efficiency of nickel metal hydride batteries is typically 66%, meaning that you must put 150 amp hours into the battery for every 100 amp hours you get out. The faster you charge the worse this gets.

The cheapest way to charge a nickel metal hydride battery is to charge at C/10 or below (10% of the rated capacity per hour). So a 1000 mAH battery would be charged at 100 mA for 15 hours. This method does not require an end-of-charge sensor and ensures a full charge. Modern cells have an oxygen recycling catalyst which prevents damage to the battery on overcharge, but this recycling cannot keep up if the charge rate is over C/10. The minimum voltage you need to get a full charge varies with temperature--at least 1.41 volts per cell at 20 degrees C. Even though continued charging at C/10 does not cause venting, it does warm the battery slightly. To preserve battery life the best practice is to use a timer to prevent overcharging to continue past 13 to 15 hours.

[Jermo]

Thanks Bob, It won't hurt me to charge at 100mAh since I generally recharge at the end of the day anyway.