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Futaba FP-S28 servo quality

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Old 04-27-2014, 05:44 AM
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Roo Man
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Default Futaba FP-S28 servo quality

I purchased an old Cub that had FP-S28 servos. I replaced with current servos but am wondering if the S28's were a good servo. I am thinking of changing the plugs and using them on throttles.

Gary
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Old 04-27-2014, 08:15 AM
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macdona
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Default old servos

I see no problem using old servos. Do it all the time. Some of my throttle servos are 35 years old and work just fine. Have occasionally used them on rudder on smaller aircraft.
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Old 04-27-2014, 11:58 PM
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Steve Percifield
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I still have some S28's working after 25 years.
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Old 04-28-2014, 04:21 AM
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Digging through my servo stash, I rently discovered a pair of 28s, that looked almost new. I installed them as aileron servos in my new Alien Aircraft Taylorcraft.

As I remember, they has a little more torque that the 148s that replaced them.
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Old 04-28-2014, 06:59 AM
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Roo Man as you may surmise from my fellow responders and I that your plan is perfectly acceptable and practical. This as long as you have the soldering skills and a supply of the modern J plug or compatible to replace the old G plugs with.

I believe the 28"s were a step up plug from the old standard at the time however my memory is vague as to specific differences. Like the others I still have many in service and not just on throttles. Between the 'old style' airtronics and the futaba 'G' it must be hundreds I have snipped and replace with modern plugs for myself and others. At least with futaba there is no polarity reversal to deal with on the futaba plugs.

Also I would recommend the best way to do the changeover is not by soldering plug pigtails at the circuit board or crimping new plugs but instead simply snipping the lead in the middle and soldering the pigtails then shrink wrap. This is a perfectly reliable and easy way to do it.

John
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Old 04-28-2014, 07:33 AM
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Rodney
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I just yesterday found several of the old S28's in my junk cabinet. Took them out, checked them and all worked very well. Put new connectors on them and will have no apprehension in using them on the slower or trainer type aircraft.
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Old 04-29-2014, 06:42 AM
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CafeenMan
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All Futaba "Standard" servos have always been good. You have nothing to worry about as long as they are in good condition.

The only thing with standard servos is their size and weight. Modern mini servos are stronger, faster and lighter than standard servos so there is no reason to ever actually buy a standard servo but if they come with something might as well use them unless you really want the weight savings.
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Old 04-29-2014, 10:34 AM
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I would think they will work fine... although a tad rougher, with a bit less resolution the a more current servo.. I'm thinking its in the gearing.. I've checked out a few of the older Futaba servos, and have several in my "servo drawer".. and memory tells me... individually they sound good and operate smoothly... but an old model servo against a newer version.. I'm thinking a newer generation servo would win out on smoothness and resolution...

Ya know though... we all used those at some point.. and will again...You'll do fine with them.. . Good luck with it.
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Old 04-29-2014, 12:11 PM
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Rodney
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Those old servos are very often as smooth and powerful as the newer ones, in some cases more powerful. Some are slower though, especially the more powerful. After all, that is why they are more powerful, they are geared down so move slower but with more power.
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Old 05-01-2014, 06:50 AM
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"The only thing with standard servos is their size and weight. Modern mini servos are stronger, faster and lighter than standard servos so there is no reason to ever actually buy a standard servo but if they come with something might as well use them unless you really want the weight savings"

If you look inside, I believe you will find that "standard" size servos have a much sturdier gear train than the smaller variety, even though torque and speed may be comparable.

Les
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Old 05-01-2014, 07:15 AM
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Les - A lot of modern mini servos are very robust. But yeah, you always need to look at the entire servo to make sure it's up to the task - speed and torque aren't everything.
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Old 05-01-2014, 06:10 PM
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+1 with all of the above post, But I have to say one more thing and I don't have a clue why this happened but I have 2 that work just fine on the bench, but if you just hold a slight finger pressure they will not move just growl, fresh batteries etc. These were a pair of elevator servo's. It is like the motors just got week.

cheers Bob T
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Old 05-02-2014, 03:38 AM
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Black Wire Disease ?

I thought that they had eliminated it, but maybe a few servos made it through without a vaccination.

I've seen these symptoms ( low power) in older Futaba 148s, even if they looked to be in relatively new condition. I also remember something they called Black Wire Disease, in servos from the era. Maybe Les, or another "experienced" modeler may remember.
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Old 05-02-2014, 04:05 AM
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Mr Crump Great idea and I did nave some of the in the old style connectors mostly wth the 148's the 2 I am talking about were S28 I/we my fling buddy and I stripped both the red and black wire's back about an inch form from both end's and no evadance of black wire,

Cheers Bob T
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Old 05-02-2014, 06:51 AM
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" "experienced""

Thanks, Tom. You could have said "one of those old farts" :-))))))))))

and yes I do remember black wire disease, but never related to servos. I am still flying some of my original Futaba 148's without qualm. That having been said, I gave an electric Grumann Albatross to my son, and early in its life with him, the battery pack failed in flight. The post mortem showed that the BLACK wire had oxidized all the way through the run.

Les
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Old 05-02-2014, 10:29 AM
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Black wire disease is a problem only when NiCad's are used and the seal on one is broken or if you are using wet cell (yes there are wet cell NiCads) and it will ALWAYS start at the battery terminal and work it's way out usually stopping at the first interruption in the circuit. At one time I kept a sample of all the black wire problems I encountered over the last 60 years but have recently scrapped them. Red (at Red's battery clinic) has some pretty good discussions on black wire disease. It was almost always caused by someone storing a system with NiCad's installed and left unattended for a long period of time.
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Old 05-03-2014, 04:58 PM
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I have had the black wire disease on a lot of battery packs, and even a switch. Not on a servo. Yet? I like the old slow servos for a throttle. Lots of my old motors can't take a quick blip of throttle without stumbling or cutting out anyway.
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Old 05-07-2014, 03:25 AM
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I have been using older standard servos for years without any problems. Sometimes I will use a newer digital servo hoping to get tighter resolution. And sometimes shaft/case wear will be large where a ball bearing servo should have been used.


Don't ever remember black wire disease in servo wire.


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Old 05-07-2014, 05:04 AM
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Thanks for all your input. Will definetly use them.

Gary
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Old 08-08-2017, 09:08 AM
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48oz
Futaba® Discontinued Servos

Great servo,I use them on 7.5 K&B outboards for steering (2) and one for throttle.
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