Originally Posted by Fixed Wing

Hi Drew,

Don't believe all the answers you get on the internet. I had 3 of the 7980's get real bad jitters, had a hard time holding center, and sometimes jumped for no reason. This was even with Hitec provided signal line boosters installed. I never did try the option of soldering a .22 tantalum capacitor between the +/- on the extension like I believe Bob did way back once.

Since I was locked into the case size of the servo I switched to the HS-M7990TH which has the magnetic encoder. So far they have been rock solid and I like them.

I have both the 7980's and 7990's and have been using them for a little over a year on two 40%ers for the elevator halfs and rudder on both planes with a couple hundred flights each, both have been good (very quite) but the 7990's seem to center better, for the cost difference between the two I would stick to the 7990's.

Originally Posted by Mrs R

Hi! Smacka,
What happened was that I posted a question asking for feed back or just asked who had done the first part of the fix and the only replies were " I bought SAVOX " or similar.

No one said they had tried to have a go, if I had a positive reply like "I want my HITECS to work I have done the first bit and would love to do the rest then I would have gone to the extra trouble and finished doing the Repair write up. All I saw was HITEC are rubbish and I am going to this servo or that, the thread fell apart.

I am still ill but have been able to muddle on " I haven't flown for over a year and that hurts"

I would have liked HITEC to have been a bit generous but that's life any way I have sent fixes to a few people who have PM'd me their email address, and I have repaired some with Denises help.

I have some servos still to send back to those who have sent servos for testing to find the faults.
I MUST SAY THAT IF THEY HAD NOT SENT THEM I WOULD NOT HAVE FOUND THE FAULTS sorry Tavis
There are things still happening and HITEC will have a new main board out when they feel it is right etc. I hope.

ALL THE BEST
Rachael

Hi Rachael:
First, I do hope for a long term speedy recovery for your health!

Yeah, the first part of your fix was to help fight the effects of the conflicting feedback signals, that of buffering the resultant jitters so that basically the servo would ignore or suppress the spiking feedback. I guess you could say the first part of the fix was a fliter of sorts that blocked/suppressed signals higher/stronger than XXX-signal. Replacing the pot/wipers covered the damaged cause by the jitters that bascially beat the heck out of the discrete components.

Your long term fix actually addressed the root cause of the errant/confused feedback signal. This stopped the jitters entirely and now the rest of the servo could live happily as normal wear and tear would suggest/dictate.

That's the Rachael we know and love. I was beginning to think you had greatly softened your position with respect to the seriously flawed G2 circuitry

Should Hitec produce a new main board that eliminates the G2 circuitry issues, I am on board. I happily used Hitec in all my aircraft before G2

Have a great day!
Bill

So far, my 7980's have been rock solid. No caps or line boosters. One year, no issues. My 7950's have the caps soldered in, and after two years , starting to get some fluttering at center, on the ground. Before the caps were installed , had major jumping issues on the 7950's. Big differance between jittering, & jumping.

Originally Posted by wylieruneyjr

So far, my 7980's have been rock solid. No caps or line boosters. One year, no issues. My 7950's have the caps soldered in, and after two years , starting to get some fluttering at center, on the ground. Before the caps were installed , had major jumping issues on the 7950's. Big differance between jittering, & jumping.

Are you running 7.4V ?

Originally Posted by wylieruneyjr

So far, my 7980's have been rock solid. No caps or line boosters. One year, no issues. My 7950's have the caps soldered in, and after two years , starting to get some fluttering at center, on the ground. Before the caps were installed , had major jumping issues on the 7950's. Big differance between jittering, & jumping.

Just a note of clarification..."jumping" is a higher amplitude "jitter". The lower amplitude "jitter" is actually more detrimental/harmful to the discrete components within the servo. Lower amplitude means higher frequency cycles, meaning the cycles are faster due to the decrease in amplitude.

So, on the ground or in the laboratory, the jitter cycle is more destructive over time. However, If you get a high amplitude "jump" in the air, it is instantly game over and the bird is coming in for an unscheduled landing

Originally Posted by wylieruneyjr

So far, my 7980's have been rock solid. No caps or line boosters. One year, no issues. My 7950's have the caps soldered in, and after two years , starting to get some fluttering at center, on the ground. Before the caps were installed , had major jumping issues on the 7950's. Big differance between jittering, & jumping.

When they start jumping you are headed into the jump and jam side of things.
Usually when they do that the servo goes 90% full clockwise and burns out half the servo.
I had a non fixed (Fitted by mistake) 7950 do that on my EF EXTRA 300 and snapped the Aileron in two. At least the plane was on the ground when it happened.

I would pull the servo and put it away for repairs. That will happen some time yet.

ALL THE BEST
Rachael

Jag01
Your message box is full and my PM bounced back please clear your message box and re PM me your Email address

ALL THE BEST
Rachael

Originally Posted by Mrs R

When they start jumping you are headed into the jump and jam side of things.
Usually when they do that the servo goes 90% full clockwise and burns out half the servo.
I had a non fixed (Fitted by mistake) 7950 do that on my EF EXTRA 300 and snapped the Aileron in two. At least the plane was on the ground when it happened.

I would pull the servo and put it away for repairs. That will happen some time yet.

ALL THE BEST
Rachael

Agreed the potential to burnout half the servo (or more ). That would be due the servo friction (binding up by overdriving the flight surface or reaching an internal hard endpoint) causing an increase in current trying to overcome the bind or friction. That increase in current heats up the servo components, quick, fast and in a hurry. The case usually distorts severely in the process, on and on...

I just have not worked it through conclusion in my brain as to what would cause the voltage to jump and hit the rail. Possibly a momentary/intermittent ground loop? What are your thoughts Rachael?

I have seen some awesome things happen when the smoke is let out of an electronic circuit

Should change the thread title. They are now old and have Parkinsons.

Has anyone sent any 7950's to Hitec for repair recently?

What was the result?

Hitec 7950 Jumping (0 min 39 sec)

just sent mine in yesterday. a123 2300 battery. not the greatest camera work but thats not jittering its jumping...this is with the booster mike sent me.

Are you using the Spektrum inline booster ? If you touch it does it stop ?

No i used the boosters Mike Mayberry sent me. It doesnt stop when i touch it only if i grab on tight it will stop, as soon as i let go it starts again.

looks like normal hitec servo behaviour to me. they're crap. no one i know over here uses them they all had similar probs. before other brands came out with better servos people used to put up with them being rubbish because there wasnt much to jump to but now with futaba, jr's new range and savox, hitecs are a servo best left for the new person in the hobby. one day the trend in europe will reach the shores of the usa. its inevitable, it always does

Originally Posted by Wayne's World

Hitec 7950 Jumping - YouTube just sent mine in yesterday. a123 2300 battery. not the greatest camera work but thats not jittering its jumping...this is with the booster mike sent me.

Didn't see and glitching / jumping in that video. That is the standard jitter that all my 7950s (10 of them) have developed after less than 50 flights. Before I installed the signal boosters that Mike provided, I got glitching / jumping severe enough that when it happened on the Elevator of my 170cc Ultimate, it would lift the tail of a 43lb airframe a full 6" - 8" off the bench.