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Futaba 149DP PCM RX & 9CAP servo check?

Old 06-18-2005, 02:14 PM
Todd D
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Default Futaba 149DP PCM RX & 9CAP servo check?

Okay this one may stump you BAX. I have a 149DP PCM RX in a Funtana90 with 5 Hitec 5645MG servos, standard throttle and a 5 cell 1700mah ni-cad-pack. When I initially installed to servo's I had one fail during installation and sent it to HiTech and they diagnosed a damaged amplifier and repalced the servo. The problem with the orogianl servo only showed up after the servo was powered up for 20-25 minutes during setup and rigging. So, now as a check on the rest of the servo's and the new one Hitec sent me I set my 9CAP transmitter to the servo check mode and let it run for about 25 minutes cycling the servo's slowly in the shop. (TX and RX Antenna fully extended). After 25 minutes or so the whole system locked up, I mean it stopped working. I shut down the servo check feature on the 9CAP and tried to run the control surfaces normally with the sticks and got very erratic operation and in some cases none at all or even uncommanded operation. Seemed to me like the RX was failing for some reason.
I immediately tried the TX on a different RX in a different plane to eliminate that and it worked normally. Also checked Tx batt and RX batt and they were both fine 9.9volt and 6.4 volts. So I shut down every thing and put it on charge overnight just to make sure. Next day I power up the system and everything is working normally, so I run the experiment again and get the same results. Erratic operation after 20-25 minutes while running the servo check feature. So I shut down again and come back the next day. (charge overnight) Once again everyhting operates normally.
This time I power up the TX and RX in the plane and manually cycle the servos through with the TX for over an hour and it works with just the sticks normally! Today I run the plane in the backyard and range check with the engine running and antenna collapsed and range check is fine, easily 100 feet.
Is there some reason the RX will stop working after extended check with the servo check feature?
Perhaps you've seen this before?
After the final test (one hour of cycling manually) and range check I feel the plane is okay to fly.
Your thoughts on this are appreciated!
Old 06-22-2005, 04:41 PM
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Default RE: Futaba 149DP PCM RX & 9CAP servo check?

We're sorry, but this isn't something we've heard of before. We don't think it's the receiver, since the receiver's decoder is always putting out a signal, regardless of whether the servos are moving or not. If there was a problem with power supply to the servos, it would show up as physical damage to the power bus on the receiver. The current used to drive the servos does not pass through the receiver, but goes through the servo power bus.

The only thing we can think of is something in the transmitter. We'd have to try one of our units here to see if we can duplicate the problem. You may wish to send us your transmitter for examination. You can also try running your transmitter only for about 20 minutes in the servo test mode and then turn on the receiver. If it continues to work for a few minutes, then we'd tend to belive it's something in the transmitter.

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