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Old Jan 28, 2013, 01:24 AM
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fnnwizard's Avatar
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By all accounts so far, it seems like the 398 is up to task. However, can any JR rep verify what is the deadband of the 398?
I know the 378s were 4 microseconds and yet they were advertised comparing to "traditional JR resolution" (which at the time I believed was superior to anyone else at 1microsecond and even less). Now these 398's are advertised as the same, so would it be ok if I assumed that the deadband on these 398s are also at 1 microseconds or less?
Surely someone has to know this and share it... or do I have to buy a servo and test it myself now .
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Old Jan 28, 2013, 01:35 AM
launch low, fly high
New Zealand, Hawke's Bay, Havelock North
Joined Dec 2004
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I've not explicitly tested my 188 servos for deadband. All I know is that they respond to a single click on the trim/centering function (which wasn't true for the 171 servo). I'd be interested in seeing what you would find with quantitative testing. I can bring one to the SWC for you to borrow/test if you wish.
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Old Jan 28, 2013, 09:27 AM
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United States, CA, Midway City
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Originally Posted by Joe W View Post
I've not explicitly tested my 188 servos for deadband. All I know is that they respond to a single click on the trim/centering function (which wasn't true for the 171 servo).
Thanks Joe for your info. On the single click trim, is your trim steps set to 1 on the JR tx? If so, that should be close to 1.00 microseconds per click.

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Originally Posted by Joe W View Post
I'd be interested in seeing what you would find with quantitative testing. I can bring one to the SWC for you to borrow/test if you wish.
That would be great! I would love to test one out. Thanks!
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Old Jan 28, 2013, 12:57 PM
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OR Tuan could quit being such a cheap ass and cough up the dough for a single 398 from Horizon..
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Old Jan 28, 2013, 03:57 PM
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United States, CA, Midway City
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Originally Posted by Avaldes View Post
OR Tuan could quit being such a cheap ass and cough up the dough for a single 398 from Horizon..
Yes, I am extremely cheap anytime there's potential for not getting minimal value from a purchase. Don't like "losing" hobby funds wantonly, direct past experience; something about a fool and his money, otherwise I will be a donkey .
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Old Jan 29, 2013, 10:35 AM
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near Sacramento, CA
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Tuan,

Given your awesome reputation for doing great tests, since JR is clueless then perhaps SUSA (who actually does read RCG threads) should be automatically giving you new units to test. SUSA's relationship with JR should be good enough to get credit back from JR for "new unit testing."

It still amazes me how backwards some of our primary vendors are in terms of customer relations...

Chris B.
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Old Jan 29, 2013, 11:56 AM
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Tuan,

Given your awesome reputation for doing great tests, since JR is clueless then perhaps SUSA (who actually does read RCG threads) should be automatically giving you new units to test. SUSA's relationship with JR should be good enough to get credit back from JR for "new unit testing."

It still amazes me how backwards some of our primary vendors are in terms of customer relations...

Chris B.
There are some things I just don't understand. With the internet age, consumers are getting very smart (well most anyway), and providing more info is better than less for sales.
You'd think that providing the deadband info is much easier than say the speed/torque values. I guess it's just not important enough of a spec for most of the manufacturers to include it, or it could be that the deadband is easily verifiable to a degree (no pun intended) by the consumers.

Granted the leaders have come a long way to disclosing specs, and JR has always been at the leading edge in my opinion.

I've been wanting to buy some of these 398's but just couldn't pull the trigger based on past epxerienced with the 378s. I just don't want more unused electronics cluttering up my bins which I really need to clean out per my wife .
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Old Jan 30, 2013, 12:17 AM
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My experience has shown the 398s work and center well, even though I have no idea what the deadband is, and have not conducted any testing other than actually flying. Just an alternative viewpoint.

Tom
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Old Jan 30, 2013, 01:34 AM
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THAT is why you buy one to test instead of 12 In all seriousness, I have heard nothing but great reviews on the 398. Seems like a real winner.
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Old Jan 30, 2013, 12:15 PM
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I have bought a few of the "servos of the future", and I won't be buying any 398 until I read some unbiased technical tests. I know that's more than I would ask from other servos, but I think that JR has to do some extra work to regain my trust.

Therefore, go Tuan! I am willing to share the cost, if you have the will and equipment to run some tests. I also volunteer for torque/current measurements.
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Old Jan 30, 2013, 01:32 PM
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I don't really understand the desire to know the dead band is. It's narrow.
The dead band was really narrow on the 378 and they have all accuracy of a drunken sailor wearing a blindfold.

The futaba s3150s doesn't have a particularly narrow dead band but it is a pretty accurate servo and has a good quality reputation.

Whether a servo can rotate to 60 degrees in 0.10 or 0.11 seconds isn't too important. I admire those people who can tell the difference though.

It's well known that manufacturer figures are not very accurate anyway. Especially torque figures.

Quote:
By all accounts so far, it seems like the 398 is up to task
Maybe it's the servo of the future?



The gear slop on the 378 wasn't anything to write home about. In that sense MKS are far ahead of the pack. Also is accuracy.
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Old Jan 30, 2013, 02:44 PM
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United States, CA, Midway City
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Originally Posted by satinet View Post
I don't really understand the desire to know the dead band is. It's narrow.
The dead band was really narrow on the 378 and they have all accuracy of a drunken sailor wearing a blindfold.

The futaba s3150s doesn't have a particularly narrow dead band but it is a pretty accurate servo and has a good quality reputation.

Whether a servo can rotate to 60 degrees in 0.10 or 0.11 seconds isn't too important. I admire those people who can tell the difference though.

It's well known that manufacturer figures are not very accurate anyway. Especially torque figures.

Maybe it's the servo of the future?

The gear slop on the 378 wasn't anything to write home about. In that sense MKS are far ahead of the pack. Also is accuracy.
The Futaba S3150 is 1 microsecond deadband, which would be considered excellent. I won't buy a servo with more than 2us deadband anymore. At 3us you can tell the difference in the flaps at various flight modes if your linkages were correctly tight to begin with.

One of the reasons why the 378 buzzed so much more at neutral was because at 4us deadband and your tx/rx was giving it a command in between the 2 spots, it does not know where to go.
Most of today's subtrims are in increments of 1us and less, with trims also at 1us or less (user adjustable on most tx's), with pots on the sticks +- 1-2 all the time.

Speed is only really critcal on ele servo... ele resolution not as much due to "gearing" of the arms.

A 1mm error in today's te could mean you are not going up in a light thermal when others would or not make it home from downwind. It used to be we see slop of 2mm before, but most builders have gotten much better.

Anyway, for the wing, it pays to be able to fine tune the te to the smallest increments = smallest deadband possible.

Quote:
Originally Posted by Francesco View Post
I have bought a few of the "servos of the future", and I won't be buying any 398 until I read some unbiased technical tests. I know that's more than I would ask from other servos, but I think that JR has to do some extra work to regain my trust.

Therefore, go Tuan! I am willing to share the cost, if you have the will and equipment to run some tests. I also volunteer for torque/current measurements.
Thanks for the offer Francesco. I'll be able to do some basic current, speed, deadband test on Joe's servo in AZ! If it passes intial tests, I'll order some standard ones to use on LiFe voltage. I don't like the HV ones on 6.6v as it looks like you are giving up 20% for speed and torque and I don't like to run Lipo in a sailplane. If you saw my servo bin you will understand why I am so relunctanct to buy servos just to test anymore ... maybe I go take a picture and post it
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Last edited by fnnwizard; Jan 30, 2013 at 03:01 PM. Reason: Added response to Francesco
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Old Jan 30, 2013, 03:51 PM
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Warwickshire, England
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Quote:
Originally Posted by fnnwizard View Post
The Futaba S3150 is 1 microsecond deadband, which would be considered excellent. I won't buy a servo with more than 2us deadband anymore. At 3us you can tell the difference in the flaps at various flight modes if your linkages were correctly tight to begin with.

One of the reasons why the 378 buzzed so much more at neutral was because at 4us deadband and your tx/rx was giving it a command in between the 2 spots, it does not know where to go.
Most of today's subtrims are in increments of 1us and less, with trims also at 1us or less (user adjustable on most tx's), with pots on the sticks +- 1-2 all the time.

Speed is only really critcal on ele servo... ele resolution not as much due to "gearing" of the arms.

A 1mm error in today's te could mean you are not going up in a light thermal when others would or not make it home from downwind. It used to be we see slop of 2mm before, but most builders have gotten much better.

Anyway, for the wing, it pays to be able to fine tune the te to the smallest increments = smallest deadband possible.



Thanks for the offer Francesco. I'll be able to do some basic current, speed, deadband test on Joe's servo in AZ! If it passes intial tests, I'll order some standard ones to use on LiFe voltage. I don't like the HV ones on 6.6v as it looks like you are giving up 20% for speed and torque and I don't like to run Lipo in a sailplane. If you saw my servo bin you will understand why I am so relunctanct to buy servos just to test anymore ... maybe I go take a picture and post it
You should use mks servos then because the slop is far less than plastic cased servos.
I don't think I have had many, if any, servos less accurate than the graupner ds3288 in terms of double centring surfaces and I doubt they all had less deadband than it. They nearly all cost less too. Deadband isn't the sole measure of how accurate a servo is.
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Last edited by satinet; Jan 30, 2013 at 04:06 PM.
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Old Jan 30, 2013, 06:34 PM
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Harbor City, CA
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Originally Posted by fnnwizard View Post
If you saw my servo bin you will understand why I am so relunctanct to buy servos just to test anymore ... maybe I go take a picture and post it
Sell those things off, Tuan....

You know, the deadband on a Hyperion servo is user adjustable with a $17 programmer.

R,
Target
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Old Jan 30, 2013, 08:32 PM
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United States, CA, Midway City
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Originally Posted by satinet View Post
You should use mks servos then because the slop is far less than plastic cased servos.
I don't think I have had many, if any, servos less accurate than the graupner ds3288 in terms of double centring surfaces and I doubt they all had less deadband than it. They nearly all cost less too. Deadband isn't the sole measure of how accurate a servo is.
I've been using MKS. I like them a lot, but I am at a delima of running regulators, or Nimh with them.
Of all digital servos I have used none had over 4us deadband. None of the ATX have more than 3 though most were 2. Before the 378's, not s single digital JR ever had more than 1us. Hyperions from the factory are 2us. Even Hitec's were 3us or lower.
You are right, deadband isn't everything, but it sure is one aspect of a great servo.
Quote:
Originally Posted by target View Post
Sell those things off, Tuan....

You know, the deadband on a Hyperion servo is user adjustable with a $17 programmer.

R,
Target
I know, I got to clean up the garage. Here's a box of just NIB servos I still have laying around with new backups in that plastic tote .
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