I to have had failures of the Jr 3421 on small 40 size ships and large gas aircraft. Some on short leads some on long leads. I could not find a common cause except the motor was froze . the highest failure rate of any servo that I have ever owned. Needless to say I have not used them for over a year now. Al Ward PS 4cell packs and 5 cell packs

In view of the comments on the JR3421s I am putting mine on long tern test on 4.8 volts, I'll report back on any problems. On my BobCat I use the JR 9411s, on rudders, fit perfectly, work perfectly, more torque than the 3421s I bought the 3421s only last November and with over 150 JR servos bought in the last 20 years I have not had a single failure, quite a record.

How did the testing of the servos turn out David?

In lew of the unexplained problems reported with the 3421's I decided to go with four of the 3301's (2 Rud, 2 Ele). I still plan on running a 6volt pack but will be installing a regulator to avoid voltage issues with the servos. What regulator would you suggest and what voltage??
Todd

I've used Jim Oddino's (Jaccio) regulators in the past and they're very good. Not sure if he has a website for ordering, but you can get them from Central Hobbies (www.centralhobbies.com)

Doug Cronkhite
Team JR

Doug,
What is the regulated output of the the jaccio regulater (not listed on centrals site). Have you ever used his perfect switch harness with the regulator built in?
TIA
Todd

I think Jim's regulators are 5.1v and yes, I've used his perfect switch. It's a very nice product using a high quality switch. I personally use the regulator with the JR deluxe charge switch myself because I like the switch and charging jack all in one clean package, but I don't think you could go wrong either way.

-Doug Cronkhite
-Team JR

I 've been away from home for last couple of days, hopefully I will get the servos rigged up today. I will test them on 4.8 volts. Shame to see any JR servos not living up to the brand's repuation for excellence in reliability, I have never had a JR servo fail in normal operation. Perhaps there was bad batch of motors.
Horizon got any comment ?

David.

Believe me when I tell you we're concerned about it as well. I've received 3 emails today from Horizon asking me for more info on what's going on. They're taking it very seriously and are testing servos in Champaign to see if there is something they can find with off the shelf servos.

-Doug Cronkhite
-Team JR

Hi Doug,

Do you happen to know what configurations they are testing ? e.g. are they doing extended duration testing with a 450 gyro, without a regulator, on a freshly charged 5-cell NICAD pack, etc ?

Any idea what the max voltage is that they test to ?

Hopefully Horizon will by now have received the first pair of servos that I returned to them. These are the ones that were dead from the get-go (tested on a 4.8v setup with no gyro). The second pair are the ones that failed in the aircraft, after 37 flights at up to 6.6V unregulated, and driven by a 450 gyro - very much like David's setup, I believe.

BTW, did DavidR return his faulty servos yet ?

Please convey my thanks to the folks at Horizon for them being so willing to look into this - it would have been oh so easy to just say "user error" right from the start. The fact that they will go to this effort for just two people reporting a problem adds to their credibility as far as I am concerned. (And note that I don't discount the possibility that the two that were on-board failures may still count as user-error due to over-voltage!)

I already gave Horizon my contact info, and they are more than welcome to call me with any questions that they may have.

Once again, for everyone else reading this - please don't over-react and assume that a few isolated failures equate to all 3421's being bad - that would do no-one any good.

Regs,
Gordon

Gordon,

The first two that went south were sent back the week after Superman by me. The last two were again on Vernon's airplane and I think he was sending them back this week but I am not sure. I will be talking to him tomorrow and I will ask him.

DR

Did Horizon indicate what the problem was, or simply fix em ?

Gordon

I had a lengthy discussion with them prior to sending them. They indicated at that time that they would tell me exactly what was wrong but they sent me 2 brand new servos within a weeks time.

More than likely they just replaced the servos so they could keep the failed ones for more testing. Gordon, send me your name/address/phone and I'll send it along to the service guys in case they need to get ahold of you.

-Doug

As a matter of interest since the advent of digital servos I have been running all of my digitals on Duralites with either 5.1 volt or 5.4 volt regulators, never without a reg. and absolutely no problems I bought a couple of 3421s for the rudders on my BobCat but upgraded to 9411s , work perfectly with a JR 1000 gyro but the rudders are VERY active.and clearly the servos are working very hard. The 3421s are now on test at 5.4 volts.


My BobCat is now equipped with Durostruts, so much better than wire struts. and will give everything a smooth ride on the ground.
BRG,
David.

Gordon,
Didn't want to come off as over reacting, my point was I would hope (which they appear to be doing) that JR/Horizon would take a serious look at these failures and try to isolate the cause, not just toss them aside as user error and move on. Although I am a futaba radio user (just prefer the programming) I do believe the JR equipment is of the higest standards, when there is a failure of multiple servos under the same conditions by diffrent modelers it definitly raises a caution flag. I have NEVER had a JR sevo fail on me, not even a dirty pot. Although I did not buy the 3421's because of these failures, I did order the 3301's instead, still trusting JR servos 100%, just being cautious until an reason for failure is found (although, over-voltage does sound like the culprit).
I would also like to convey my thanks JR/Horizon for taking the time to look into these failures, It shows their dedication to providing us the highest quality products available.
Please keep us informed...
Todd Witkoff

Originally posted by lov2flyrc
Gordon,
Didn't want to come off as over reacting, my point was I would hope (which they appear to be doing) that JR/Horizon would take a serious look at these failures and try to isolate the cause, not just toss them aside as user error and move on.

Sorry Todd - I did not mean that remark directed specifically at you - I meant it as a caution in general to everyone reading this thread. Forums such as this are an incredibly valuable way for us to share information, but its also very easy for things to get a bit out of hand if the whole context is not considered.

Although I am a futaba radio user (just prefer the programming) ...

Aww man ... Todd... you are one sick dude !! ;-)

Just kiddin. Personally, I find the Futaba programming to be a pain, but that's probably just because I've spent a few years designing user-friendly interfaces for software, so it annoys me to see hardware with great capabilities hampered by a user interface that (to me at least) doesn't live up to the high standards of the rest of the radio. Anyway, that's another, very long, story... so I should just shut up about it right now ! (and at the same time, I should probably run for cover!) BTW, I have a Futaba WC2 in my Raptor.

when there is a failure of multiple servos under the same conditions by diffrent modelers it definitly raises a caution flag.

Absolutely - and caution is always good. I was just trying to ask folk to draw a line between caution and panic ;-)

just being cautious until an reason for failure is found (although, over-voltage does sound like the culprit

Again, can't fault your caution at all.

While over-voltage can't be the problem for my two servos that were dead right out of the package, it certainly could be at least part of the issue for the other 2 that I had fail in the aircraft, and the 4 that David/Vern had fail in theirs.

Doug earlier indicated that he has run 5-cell packs unregulated a lot, and not had any servo failures caused by doing so. Not sure though, if he has run the 3421's that way, and had them gyro-driven. That may be an important distinction, because as Tony pointed out earlier, while the aircraft has the gear down, the gyro is making the servos work more. More work, at higher voltage (and hence higher current) = more heat, etc.

While Tony does run 3421's unregulated in his Bobcat rudders, driven by the gyro in the same way, he is running Duralite's rather than NICADS, which I believe he said peak at a LOWER voltage than the nicads - perhaps just low enough to make a difference... ? IIRC, David indicated that both times they had failures, it was with a freshly charged RX battery; with mine, it was the second flight after charging. So, it could be that the issue is simply caused by a combination of unregulated higher voltage and constant workload that the servos see while driven by the gyro... or the gyro itself could be affected by the higher voltage, causing it to drive the servos harder than they like... (which could help explain the simultaneous hard-over of both rudders).

Generally, I try not to speculate about causes, because it can lead to a whole lot of exaggerated what-if's that bear no resemblance to reality, and which can easily do more damage than good. I've thought long and hard about whether to post the above speculation, and the only reason that I finally decided to go ahead and post it is that I hope it may reinforce the point that the few on-board failures we've seen probably happen in extremely isolated circumstances which can easily be avoided.

I'm putting my money on these servos working just fine now that I'm running regulated. (16 flights on the new 3421's so far, and nary a twitch from them).

Later,
Gordon

I have now run my 3421s on a regulated Duralite (5.1 volts, nomimal 5.37 measured) for over 6 hours. Both got very slightly warm, as did a 9021 on parallel test. As one would expect from JR, everthinbg is fine, test discontinued. I think very high voltage coupled with very active gyro driven rudders most likely cause for simultaneous failures reported earlier. (both servos failing at identical times under identical conditions says a great deal about JR's consistency) The rudders on the BobCat are unbelievably active but just how active is the tail servo on a helicopter ?
David G.

The tail of a heli is generally very active, but we're also not running up to 100% gyro gain continuously either. The only time I ever ran that high was in a tail locked mode for advanced 3D tumbles and such. Normally I wouldn't run that high. But also, I never ran this servo. I always used the 8700G for tail rotors, but these are $250+ if I remember right.

I think your assumptions might be correct however but I prefer to let service decide for sure.

-Doug