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HS-5485HB Problem

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Old 01-06-2018, 02:53 PM
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Default HS-5485HB Problem

Was setting up a new plane with a Futaba receiver. Initially installed a couple of HS-5485HB from a previous plane, but they would not operate properly. They would twitch a bit, then nothing. Thought it was the receiver so switched to another one. Same problem. Hmm. Took a new servo out of the box. Still nothing. Transmitter? But wait. The 225MG servos were okay. Plugged the NIB 5485 into the HPP-21 servo tester. No sweep!! But the 225 in with it worked fine. Plugged in the 5485 alone, pressed Refresh and the message came back that a digital servo was connected, but still the servo would not step or sweep. Same problem with two more NIB 5485's. What's going on?

Of course Hitec is closed today. Anyone here have suggestions (other than Buy Futaba!)? I've used Hitec servos, including the 5485, for years with nothing but good operation.
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Old 01-07-2018, 02:14 PM
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Just to add to the problem, two of the four new servos I tested are not recognized as digital servos by the HPP-21 tester/programmer. I do notice that some of the internal electronics are working as I can't rotate the servos when they are plugged in.
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Old 01-10-2018, 12:13 PM
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What voltage are you operating the servos at? 2 servos in a row to have the same issue is exceedingly rare.
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Old 01-10-2018, 03:30 PM
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Using a 5-cell NiMH battery. During the tests, I measured the voltage at the pins from 6.43 to 6.48 volts. Tested all 11 of my NIB servos and they all show the same problem. The HPP-21 sees them as "Digital Servo connected" but they will not sweep and they do not hold position. Hook up an analog servo and it sweeps properly and is identified as analog. A Futaba 3151 digital servo operates properly but I did not check if it was seen as digital. If I try to program the servo, I can set Failsafe to "On" and the rotation to CCW and these will show after I unplug and reconnect that servo! However, when I exit the programming I get a message that the servo is disconnected, however "Refresh" says a digital servo is connected.

The tally is now 11 NIB and 3 used!! The used ones are from a plane that lost control of ailerons and elevator (where the 5845'a were installed). I find this hard to believe as well but, the servos would not work on two different radio systems and on the HPP-21. Other servos, both digital and analog, work correctly on the HPP-21.

BTW, these servos were for two planes I'm trying to get airborne! I have nothing to replace the 5845's with so i am dead in the water (actually on the ground)

Was packing up all the servos to ship them back to you but, like you, I can't believe they all failed.

Need a bright idea right about now.
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Old 01-12-2018, 02:31 PM
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We have never recommended a 5 cell battery to be used with the HPP-21, roughly 6 volts is its maximum operating voltage. My best guess is that you're pushing too much voltage to the HPP-21 which is causing it to brick the servos. Try a 4 cell receiver battery and see if it still continues this behavior.
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Old 01-12-2018, 03:27 PM
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I'll give it a try (if I can find a 4 cell pack), but the servos exhibited the same behavior with two different radio systems with 5-cell batteries. That's what started me checking them out with the HPP-21 which, by the way is rather useless if it can't be used with a 5 cell battery. Pretty well everyone is going to 5-cell NiMh, two-cell A123....
Or does this mean that the 5845 can't be used with 5-cells?

Just checked the user guide for the HPP-21.
"Required Optional Parts (..)
-
-
One 4.8V or 6V "receiver battery"

Yes, there is a recommendation for 4.8 volts but it says that it may be used with a 6V pack for servos rated at 6V. It also says to make sure the pack is fully charged. It works fine with JR (DS821) and Futaba digital servos and the Hitec analog servos I have. Also, the data sheet with the 5845 says it can operate at 6V (nominal) range. Looks like I need to ship back 14 servos and the HPP-21.

Frankly, my opinion of Hitec is not as high as it was before.
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Old 01-15-2018, 11:14 AM
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Just to add to the confusion (and perhaps provide an answer), I tried out three of the servos on my older Futaba 72MHz system. They work as they should. I'm now wondering if the 5845 is one of those servos that requires a higher drive voltage than normal. The Futaba manual mentions that some servos will not work with modern 2.4G receivers as they have gone to slightly lower drive voltages. This may explain why they would not work with the HPP-21 if it also provides a lower drive voltage. If this is the case, I have a very expensive trash pile of 14 useless servos. Unfortunately, I do not have an oscilloscope to measure the drive voltage from the 2.4G and 72M receivers.
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Old 01-17-2018, 01:24 PM
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What Futaba receiver are you using? There are a couple that can only be used with extremely high refresh rate servos of which the HS-5485HB is not. The fact that you say your 72mhz system works fine with the servos but not your 2.4 system leads me to firmly believe the cause of your problems is the 2.4Ghz Futaba receiver, not the 14 servos. It is impossible for 14 servos in a row to exhibit the same exact characteristics out of the box, from any brand.

Last edited by Xpress; 01-17-2018 at 01:28 PM.
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Old 01-19-2018, 03:04 PM
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The situation has gone from frustrating to confusing, which I guess is an improvement. The good news is that its working. The bad news is that Im not sure why. Some of that is below. Sorry for the long dissertation but I'm trying to give the whole story in one place.!

System is a Futaba 10CAP transmitter and initially an R6014FS receiver, then an R6008HS. Receivers were properly bound to the transmitter. I was setting up a new plane on the transmitter, went in to Parameters, reset everything on that channel and checked to make sure Modul was set at 2.4G/10CH. Plane was set up for split ailerons and split elevators as Id done on other planes. The elevators and throttle were on analog servos and worked fine. The rudder and ailerons with the 5485s sometimes twitched, but did not work properly, even when plugged into the channels where the analog servos worked! Also, even when powered up you could rotate the output without a lot of effort, like when they were not plugged in. Switched out the receiver, but the 5485s still did not work. Tried a couple of NIB 5485s with no luck.

Pulled out the HPP-21 in test mode, and the servos would not work properly! However analog and other brand digitals worked! By now I was going nuts! Plugged the older (used) 5485s into an older plane on 72 and they worked! All tests were done with (different) fully-charged 5-cell NiMH batteries.

Went to see a local guru to see what his radio (also a 10CAP) would do. Took the used servos as well. He mentioned that with his 10CAP, sometimes you needed to go through setting the parameters a couple of times before they stuck. Did that a few times and everything worked!! Came back, plugged the servos into the HPP-21 and they worked! All the others did the same.

So the remaining questions are:
  1. What was the transmitter doing that blocked the 5485s, but left the analog servos working?
  2. Why did the HPP-21 somehow get into a mode where all the 5485s (4 used, 11 NIB) tested bad, but the analogs and two other digitals tested fine?
  3. Is the setup safe to fly?
I use Hitec servos exclusively, except for a few planes I bought with other (usually Futaba) brands. What worries me is that the plane those used 5485s were in, crashed from loss of control not, as is usually the case, operator error.

Hopefully this closes the issue but, if some of you have an explanation, I'd like to hear it. I did send this to Mike at Hitec service as well.
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Old 01-23-2018, 02:46 PM
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This is an extremely confusing one, I dare say you may have received a defective HPP-21, but there's just no possible way 14 servos in a row were bad. Consider me completely stumped..
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Old 01-26-2018, 12:56 PM
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I am stumped as well. I've gone through the setup on the transmitter a number of times and the problem does not reappear. There were three used 5485's installed in the plane, along with 3 analog servos. I suspect that somehow, the programming in the digital servos was disrupted by the signals from the transmitter. When I hooked them up to the HPP-21, they somehow disrupted it. I did try to go into the programming when I was checking out those servos and got inconsistent results. When I got the transmitter sorted out, the used 5485's worked normally with the receiver, then did also with the HPP-21. And the NIB ones then tested normally. A rather curious point is that the HS-7955TG servos that I checked out on the HPP-21 while it was "ill" checked out okay!

The good news, if there is any, is that the problem appeared as soon as I turned the system on. However, I will be nervous for the next flights!!

I appreciate the support from Hitec in this issue and with the very few issues (mostly crash related!) I've had in the past.
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