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Measuring transmitter battery voltage - 12/13/2012 4:28 AM   
jeeper80


 

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From: Kekaha, HI, USA
Status: offline 		I was given a Tower 40 trainer with an old Tower 3000 series 72 Mhz FM radio system that I just replaced the batteries on.  Thinking that I could measure the transmitter battery pack voltage through the charge jack, I bought a Hobbico Expanded Scale Voltmeter with a set of leads that has a Futaba charge plug on one end.  When I stick the charge plug in the transmitter's charge jack, I get nothing.  The battery has a full charge on it and the transmitter's meter indicates a full charge.  Is there a diode in the charge circuit that is preventing me from see voltage on the ESV?

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RE: Measuring transmitter battery voltage - 12/13/2012 4:44 AM   
jester_s1


 

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Status: online 		Yes there is. Doesn't your radio have a battery meter on it? That's all you need to make sure you have enough charge to fly.

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RE: Measuring transmitter battery voltage - 12/13/2012 4:52 AM   
jeeper80


 

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Status: offline 		Thanks Jester,  that's what I figured.  I thought it would be good to check the battery under load but it's new and probably not necessary .  I used to have old Futaba FG series radios (gold series) and I think I was able to check through the charge jack. It's been a long time so my memory might be a litle rusty.

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RE: Measuring transmitter battery voltage - 12/13/2012 1:22 PM   
jetmech05


 

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Status: offline 		mostr radios either have a low voltage warning (bells and whistles) or a meter.....I have never had a transmitter ever get close to low voltage.

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RE: Measuring transmitter battery voltage - 12/13/2012 1:35 PM   
Lowvoltage


 

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From: Clinton, IL, USA
Status: offline 		There is probably a diode in the charge circuit of your transmitter that will allow charge current IN, but does not allow current OUT unless you remove the diode from the circuit.  With my transmitter, if I want to cycle the batteries I have to remove the pack from the transmitter and plug it into the charger with a servo type connector. 


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RE: Measuring transmitter battery voltage - 12/13/2012 1:46 PM   
flyinwalenda


 

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Status: online 		If the analog meter on the radio is showing full charge then I would say you are good.


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RE: Measuring transmitter battery voltage - 12/13/2012 1:46 PM   
jester_s1


 

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Status: online 		The meter on the transmitter is a load test. You have to remember the unit is on when that meter is working.

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RE: Measuring transmitter battery voltage - 12/14/2012 2:41 AM   
JPMacG


 

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From: Ivyland, PA, USA
Status: offline 		That is the same trainer and same radio I learned on. Yes, there is a diode in the charge jack circuit. If you want to check voltage via the charge jack you would need to short out (jumper) the diode. But there is no need to - the little meter on the transmitter is what to use.

Directions for jumpering the diode have been given many times here. Do a search if you're interested in doing it.

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