TH9x Power switch and charger Jack Mod

General mods that are considered worth doing; regardless of the end firmware you use.
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TH9x Power switch and charger Jack Mod

Post by Helle » Sun Nov 11, 2012 7:57 am


does anyone know the homepage of this one?

I have only 2 pictures of the Mod

Original Power and charger jack
Modified Power and charger jack

Most destroyed th9x are from wrong polarity at the charge jack (or not?) with bridged diode

How can we change it to a safty charger system.

Power system needs an upgrade

ok , now I found it: ... 2&page=846

Modified TH9x Power flow.jpg
Original Th9x Power flow.jpg

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Re: TH9x Power switch and charger Jack Mod

Post by Kilrah » Sun Nov 11, 2012 8:26 am

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Re: TH9x Power switch and charger Jack Mod

Post by ShowMaster » Mon Nov 12, 2012 4:13 pm

The original charge circuit as you can see travels through (I use hole flow + to - not electron flow - to +)
the diode and many small connector pins on the circuit board to get to the battery.
This circuit is typical of the circuits used with or without the diode, usually with, for most TXs is the last 20 years. It was designed around nicad packs charging at 50-120Ma, and not for fast charging. The diode was added to prevent one from shorting out the charge jack or reverse charging and drawing AMPS through circuits designed to carry 200-300 Ma for normal operation.
The diode has a limitation of 1Amp and does drop .7v. This to be safe, limits fast charging to less than 1A to be safe. It also can "spoof/trick" some smart chargers to over or under charge.
Eliminating or shorting the diode out removes the 1A charge limitation but then the tx wiring becomes the "fuse" if too much charge current it used or worse, the charge jack is shorted or connected in reverse to the charger.
So without rewiring the charge path the risks are shorting out the jack and frying your internal tx wiring, or reverse charging the battery pack.
When I do remove the diode I jumper it with a 3A Pico fuse instead. If I do blow the fuse and not the wiring I still have the normal diode path to keep me charging as a backup.
The rewiring of the charge circuit to bypass the diode and most of the critical tx wiring is, in my opinion, the best option. I would also add the fuse and after it a diode from the battery side, wire it Cathode (White Bar) to + lead and Anode to ground. This way if the charger is connected reversed the diode conducts and the fuse blows hopefully before the new TX charge circuit wiring and also hopefully, with the tx off!
The fuse also protects the circuits from shorting the charge jack.
The fuse should have a current rating maybe double of the charge current that could be used in reverse. Depending on the chargers used it may not be posable to charge in reverse but then again??
I've repaired many burned tx wiring over the years so some are able to do the impossible it seems.

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