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Killed 4 servos at once...

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Old 08-01-2007, 08:57 PM
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domanonamous
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Default Killed 4 servos at once...

Is it possible that 4 AA batteries fried all my electronics? The switch got bumped "on" in transit and not found until the next day. New batteries installed and now 2 servos barely respond (analog), my 333oz digital is out and a 645mg is out completely as well. Swapped rx's and same response. I think my gyro and receiver are good but nothing else. This is going to be an expensive lesson learned. To me it seems unlikely that all 4 servos fried from the power of 4 AA. Murphy's law says it probably did. ANY input to this is appreciated. BTW no more switches, I'm pulling the batteries from now on.
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Old 08-01-2007, 09:29 PM
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Default RE: Killed 4 servos at once...

I have left transmitter and receiver switches on until batteries were dead, more time than I can count. NEVER any damage, to any components, except the batteries.
Only thing that MAY have happened, that I can think of, is if the servos were driven over hard against the stops. That could possibly damage the servos, and some receivers, do drive the servos over hard without a Tx signal.
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Old 08-01-2007, 09:31 PM
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Default RE: Killed 4 servos at once...

Maybe I'm wrong but i find it pretty hard to believe that 2 servos died and 2 barely work from leaving the switch on. Have you eliminated the switch and used another receiver to double check everything? What radio system are you using? If it's spektrum based the batteries may not be supplying enough power to the receiver. Also, if you just put a brand new battery on to try, it may not be delivering full power to everything. It would need to be slow charged and cycled??
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Old 08-02-2007, 12:50 AM
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Default RE: Killed 4 servos at once...

2 servos (the big ones) probably were pushing against the stops. The other two had very little load, and still respond but take about two seconds to travel. The receiver is a FMA M5 (I believe) and I'll be very thorough tomorrow when I revamp the electrical system (to eliminate the switch). I have 2 other receivers to swap (both using a different crystal). Murphys Law says the tx probably went out, coincidental to any perceived problems I might have. Thank you for your time, I'll update this thread with any results.
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Old 08-02-2007, 07:43 AM
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Default RE: Killed 4 servos at once...


ORIGINAL: domanonamous

Is it possible that 4 AA batteries fried all my electronics? The switch got bumped "on" in transit and not found until the next day. New batteries installed and now 2 servos barely respond (analog), my 333oz digital is out and a 645mg is out completely as well. Swapped rx's and same response. I think my gyro and receiver are good but nothing else. This is going to be an expensive lesson learned. To me it seems unlikely that all 4 servos fried from the power of 4 AA. Murphy's law says it probably did. ANY input to this is appreciated. BTW no more switches, I'm pulling the batteries from now on.
I have seen servos hammer back & forth lock to lock, when the transmitter is shut off. It is possible, in your absence, the receiver found a hint of a signal and responded to it by jittering the servos. Under those conditions, I could understand if some gears lost teeth, or servomotors were held at full deflection against the stops until they overheated.

Bummer.
Dave Olson
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Old 08-02-2007, 09:27 AM
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Default RE: Killed 4 servos at once...

I've taken 2 servos apart (no missing teeth) or anything obvious. I'm leaning toward Scars overheat theory but I am having a problem applying this to 4 servos including one with an aluminum heat sink! Seems unlikely and unlucky. Would a burned out servo "smell " when taken apart? I am going to find another tx to try since I've had the same results with 2 receivers. (Coincidence theory).
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Old 08-02-2007, 11:47 AM
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Default RE: Killed 4 servos at once...

Starting with trouble shooting 101, check the power source. I recently switched back to the stock set up with the AA's in a holder. I have two of these identical battery holders, one as a back-up. I know the batteries are good, so closer inspection reveals that the substandard (cheap) wires/solder connection was down to a few strands on BOTH battery cases. It looked good until I forced the issue with a good wiggle test revealing broken wires at the insulation. I put the old ni-cads back on and WHEW! I think its going to be OK. Thanks for your help. Common sense prevailed. This was the cheapest fix possible and I "saved" 4 servos at once.
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Old 08-02-2007, 02:09 PM
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Default RE: Killed 4 servos at once...

That's better[8D]
Now please throw out those battery cases, while many use them in transmitters (arguably a bad practice), using them for an airborne receiver pack is a terrible idea, it's not an issue of will it cause a problem, only of when
Good luck,
Pete
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Old 08-03-2007, 06:10 PM
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Default RE: Killed 4 servos at once...

if the receiver was an FMA M5 then the servos shouldn't have banged against the stops or even moved at all with the Tx off.





dave
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Old 08-04-2007, 04:32 PM
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Default RE: Killed 4 servos at once...

We should come up with some harsh punishment for people who use snap-in battery holders for airborne packs. Let's see, we could catch him at the field and break off his transmitter antenna. [img][/img]. Maybe someone has a better idea.
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Old 08-12-2007, 04:02 PM
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Default RE: Killed 4 servos at once...

Now everything is suspect. I want to upgrade my switches too. I have a need for 2 switches, (one for rx and another for servos). Is there a good switch for this. A DPDT will do 2 different circuits right? Is there one for rc applications?
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Old 08-12-2007, 08:20 PM
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Default RE: Killed 4 servos at once...

Standard flightpack switches ARE DPDT. They switch both the POS and GND leads.

Why do you feel that you need a seperate switch for the RX & servos? In 99% of installations the servos draw their power from/through the RX with no problem.

You also need to tell us what you are using all of this in, what electronics you have and why you are trying to be so cheap and using inferior equipment like regular AA baatteries and snap-in holders. Sorry to be so blunt.
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Old 08-13-2007, 07:25 AM
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Default RE: Killed 4 servos at once...

Bruce,
Never seen a switch harness that used the two poles of the switch for the neg/pos, normally the two poles of the switch are connected in parallel to provide redundant switch contacts, if it were connected to switch both neg and pos leads it would be only half as reliable as a single pole switch in the positive lead, not a good idea
Pete
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Old 08-13-2007, 10:46 AM
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Default RE: Killed 4 servos at once...

I am installing an FMA opto4. It isolates 4 channels optically from any RF that might feed in from servo wires to the rx. In order to fully isolate the systems they recommend 2 batteries.
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Old 08-15-2007, 01:45 PM
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Default RE: Killed 4 servos at once...

I had some hitec didgitial servos go out because I had the fail safe set wrong and when I turned off the radio they went into a position that caused high current
burnt the servo out in less than 10 minutes
hitec didgitial servos automaticaly hold the last known position once the power is off
6 volts 3 amps that is 18 watts
touch a 18 watt light bulb and it is very hot
now confine the energy in an even smaller object
you have just invented a soldering iron

joe
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Old 08-15-2007, 02:01 PM
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Default RE: Killed 4 servos at once...


ORIGINAL: polikarpov i16

I had some hitec didgitial servos go out because I had the fail safe set wrong and when I turned off the radio they went into a position that caused high current
burnt the servo out in less than 10 minutes
hitec didgitial servos automaticaly hold the last known position once the power is off
6 volts 3 amps that is 18 watts
touch a 18 watt light bulb and it is very hot
now confine the energy in an even smaller object
you have just invented a soldering iron

joe
This is why it is ALWAYS: RX off first and then the TX. Only one allowed exception, a crash.
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Old 08-26-2007, 08:13 PM
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Default RE: Killed 4 servos at once...


A couple of years ago I bought 9 Hitec servo's for my T34B. I tried all of them once a couple of years ago then put them away in a box. Now that I'm working on my T34B again, I took them out of the box and installed them in the plane. 6 of them are 635 KG's (Karbonite gears). 3 of the 635 KG's do not work. The ones that do not work appear to move against the stops when the power is turned on. I'm using a Hitec 8-channel receiver and have a 4.8 volt battery which is probably not enough for all of those servo's (?) Have ordered a 6 volt battery.

But I tried those bad 635KG servo's on another plane....they still don't work.

So what the heck could happen to those servo's while they're sitting in the box? (Do they come out at night and wrastle? ) But seriously, I assume I stored them away in a hard-against-the-stops state.

How do you set the fail safe on a Hitec digital servo?

I think I'll replace all of my 635KG's with 645MG's just to be safe.

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Old 08-30-2007, 12:06 AM
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Default RE: Killed 4 servos at once...

you set the fail safe with there programer
I think it is set at last known position from the factory
the programer is cool

even though I use it more for just testing servo's
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