I have a plane that I recently acquired. When the battery for the receiver was removed, the terminal had been melted a little. I did not think much of it at the time, could have been done when putting heat shrink on it. It had a 5 cell Nicd battery. I replaced the battery with a Fromeco 5600 7.4v pack I have the battery run to a M.P.I switch/charge jack, then to the regulator, then to a new receiver. After about 30 seconds the heat sinks on the regulator become very hot. It is the adjustable type regulator. So, my question... is this normal, if not where could my problem be? All the servos are working correctly. Maybe a bad servo motor?

Thanks for any help.
-C-Man-

What is the output voltage of the regulator set to? A fully charged Li-Ion pack can put out around 8.4v and the lower the regulator is set, the more voltage that will have to be bled off in heat.

I have it set to 6-volts.

What kind of regulator is it?

If it's the MPI one with red shrink then you are operating well within the limits so one of the components probably went bad. Most regulators should be able to handle these numbers without heating up too much.

Also,

How hot is hot? Can you hold it still or is it too hot to touch for more than a few seconds?

What kind of regulator is it?

Yeah, I guess that would be useful information. It is a Smart-Fly adjustable regulator. (With the yellow shrink wrap)

It is hot (don't have a temp gun) but I would guess about 120* or so. Not hot enough to burn you, but enough to let you know it is pretty warm.

If it is a bad servo, how do I check them. Can I use an ohm meter? What reading do I look for? I know it is not a dead short... Well, I think I know All the servos are working, so I would think no dead short.

Canardman.

How hot is hot. Burn the fingers hot or just super warm to the touch. If your using a freshly charged battery pack your turning some 2.4 volts into heat. If you were to lower the output from 6 volts to say 5 volts your dumping 3.4 volts and that regulator is going to be even hotter.

I have seen these regs get hot with large battery packs fully charged. But dont panic.

Set up a voltmeter in the battery circuit before the regulator and turn your model on. Waggle servos, do what ever you can and run it for 20 minutes or so. Then when your pack voltage has settled to around about 7.6 volts or such touch the regulator again and see if its running cooler. It should.

If your concerned about an after regulator load then I suggest you look for a pwer meter or something that reads volts, watts, amps etc in line and real time. You can find them at Eagle Tree, Medusa research etc and they are really invaluable when it comes to setting up your planes.

As a rule of thumb with a model on the bench and everything running I look for a neutral current draw of less then 200 Milli Amps. Any more than that indicates servos fighting each other, maybe a bad servo pot or a sticky flying surface.

If you have a good setup you can have the no load current draw as low as 100 MaH.

But first step mate would be run that battery pack down a tad to the operational; voltage and see what gives. Another one is raise the regulator output to 6.5 volts so you get the output voltage closer to the input voltage. The lower the difference the less heat you will produce.

Hope this helps some.

Ended up being a servo going out. In the final setup, the choke servo ended up going out. After that, the reg stayed much cooler.