SK-720 has cost me $1200+ so far. Please help!

[Ian Davidson]

Well foks, yesterday I received my replacement SK-720 from Skookum, along with an import duty bill of $30, which I can but add to the rest of my SK-720 'tab'.

I'm pleased to report this new SK-720 exhibits neither the lop-sided swash-plate movement on power-up, or the Windows error message telling me "the gyro has failed to initialise", both of which are excellent steps in the right direction!

However, today I noticed something really rather alarming, not connected with the SK-720, but with my 'Perfect Regulator' regulator. I have absolutely no idea how I could've missed this before, but it only came to my attention this evening while I was setting up the helicopter in a darkened room. Look at power LED on the regulator!



This is with a fresh set of battery, but the flicking 'appears' to only start once the regulator has been on for 30+ seconds. I'm wondering if it could be a dry-joint which only starts to break-contact when things warm up, but no amount of moving or stressing of the cables going to/from the regulator appear to instigate or halt this power LED flicker.

I think it's time to email 'Perfect Regulator'...

[georgi UK]

=] Ian hi, its always good when we get this kind of feedback, thanks. sort out the reg and get a maiden vid on here would be even better!!

georgi UK

[perfectregulators]

Ian,

The flickering red light on the regulator may just indicate a faulty led. I only say this because on the video that shows the red led on the regulator flickering, the other leds are solid. if the 5v output of the regulator was causing this issue, you would also notice the other leds flickering along with it.

[AnTi Taco]

i know im late comer to this thread but i would ditch the 720 and get a VBAR or even a beast x...out of all my FBL units i have i dislike my 720 the most..its just too dam sensitive to vibs and i just don't like how it feel in general to my VBAR

vbar
beast x
Skookum 720

the order i rank them

[Thunder Fighter]

Originally Posted by AnTi Taco

i know im late comer to this thread but i would ditch the 720 and get a VBAR or even a beast x...out of all my FBL units i have i dislike my 720 the most..its just too dam sensitive to vibs and i just don't like how it feel in general to my VBAR

vbar
beast x
Skookum 720

the order i rank them

I have all three of those as well but rate them:

Skookum 720
VBar 5.1
MicroBeast

The Vbar and Skookum were neck and neck when Vbar went to 5.1 but with the release of v3 the Skookum has jumped back in front again for me. But all of them are good, the MicroBeast while not the most connected is the most plug and play. At the level of these current FBL controllers it comes down to personal preferences to which suits your flying style the best, although the Vbar and Skookum are more tunable.

As each of them upgrade firmware the order of preference may change as well. BeastX are about to go to V3 so it may bring it up another level.

//Dennis.

[Inverse]

Originally Posted by AnTi Taco

i know im late comer to this thread but i would ditch the 720 and get a VBAR or even a beast x...out of all my FBL units i have i dislike my 720 the most..its just too dam sensitive to vibs and i just don't like how it feel in general to my VBAR

vbar
beast x
Skookum 720

the order i rank them

Skookum, the Linux of the gyro world.

[Ian Davidson]

Originally Posted by perfectregulators

Ian,

The flickering red light on the regulator may just indicate a faulty led. I only say this because on the video that shows the red led on the regulator flickering, the other leds are solid. if the 5v output of the regulator was causing this issue, you would also notice the other leds flickering along with it.

Many thanks for your feedback. I'm going to put a scope on the 5V (and 6V) output today to see if the LED flicker bears any resemblance to the trace. This latest revelation is of great concern, as it appears many of my SK-720 woes are connected to it mysteriously 'browning-out'.

Is the power LED in parallel with the regulated 5V output, or does it source its power before either the 5V (or 6V) regulator?

[perfectregulators]

Ian,

The led is ran parallel with the 5v output. You should see between 4.95v - 5.05v on the 5v side. The cyclic servo bus doesnt affect the 5v bus. Upon testing on the scope, please post your results so we can also know whats going on.

[Ian Davidson]

Well, it appears the flickering power LED on the Perfect Regulator is a red-herring. Although the LED didn't flicker when I recorded the video below (typical!) it did do both before and after and yet the trace on the scope registered 5V throughout.

Voltage dips of approx 100mV can be seen at a frequency of 300Hz, but I guess this must be the SK-720's packet frequency to the servos and so is to be expected. At around 0:13 I trash the cyclic stick vigorously, but again the voltage doesn't drop by more than 130mV throughout.



I must say, I have never experienced an LED apparently failing like this (my experience is they either work or they don't), but that aside, it appears the Perfect Regulator is working correctly and as expected.

Oh well, now I have my replacement SK-720, tomorrow I'm going to take my life in my hands (and that of my gas turbine helicopter) and attempt a test flight. If it craps out on me again, I have no idea what I'm going to do...

[perfectregulators]

Ian,

Thanks for posting the results. Its always typical when there is an issue, or what seems to be one, that when it comes to testing it, that it goes away. It like having your vehicle making a weird noise, taking it to the mechanic to be looked at and it goes away before getting there, lol...

[Ian Davidson]

Originally Posted by perfectregulators

Ian,

Thanks for posting the results. Its always typical when there is an issue, or what seems to be one, that when it comes to testing it, that it goes away. It like having your vehicle making a weird noise, taking it to the mechanic to be looked at and it goes away before getting there, lol...

Yes, that is very true! I definitely saw the LED flicker while the scope was attached and noted the trace remained constant, I just failed to catch the two events occurring at the same time on film!

[perfectregulators]

What all do you have connected on the 5v bus side?

[Ian Davidson]

Originally Posted by perfectregulators

What all do you have connected on the 5v bus side?

Just the SK-720 flybarless gyro and tail servo. The cyclic servos are powered from the 6V.

[Skookum]

Ian, I am still convinced the problem is with servo-rail power. Until it has been isolated on the bench to somewhere on the heli or your old unit, I'm worried it will happen again. Hopefully we will receive the old unit soon to check over. If you do go ahead, please be sure playback-logging is on for your next attempt.

You wrote earlier:
>Also, why would the SK-720 ever allow itself to stabilise a helicopter when the gyro knew it wasn't right in itself (the error message on the PC saying "Gyro failed to initialise") ?? Hmm...

Re this warning, it doesn't necc mean there is a real problem, and I do not think this is related to your heli's issues. The unit will not swash bump and will show an error if the init-error happens in flight mode. It will still try to fly the heli if the sensors are working but not ideally calibrated (which yours appeared to be) because for all the unit knows it just woke up after a brown-out-reset in flight, and needs to do its best to make the heli flyable. But if it does see the sensors fail, it kicks over into a less-stable but still flyable fail-safe mode that ignores the failed sensor.

[Ian Davidson]

Firstly, many thanks for sending out the advance replacement like you did. Great service!

Hopefully you'll receive my original unit back very soon and will be able to perform an electronic autopsy on it, which although I hope otherwise, will no doubt conclude with a no-fault-found.

I'm kind of stuck now between a rock and a hard place. With my new SK-720 fitted and seemingly behaving as it should, the regulator also seemingly behaving as it should (albeit with an undiagnosed power LED oddity), a brand new GEN ACE 4000mah 2S powering the lot, I'm keen to see what happens. However, with no absolutely no conclusion as to what has been going wrong (other than I agree it is definitely power related) and a $6k+ fire-breathing helicopter at risk (not to mention my own personal safety), to say I'm apprehensive doesn't even approach it.

Hmmm, perhaps it's best I wait until you get my original SK-720 back after all...

[georgi UK]

=] Ian hi, I just reviewed the screen shots on the front page of the thread to refresh where you are at now, not much farther on by the sound of it??!

for me I would secure the heli to the deck or fastened a rig, to run a voltage log before I attempted any sort of flight. perhaps fit shorter blades to load the system a bit. what do you think??

georgi UK

[Ian Davidson]

Hi Georgi, I'm definitely further forwards as I now have a replacement SK-720 from Skookum which exhibits neither the lop-sided swash-plate movement on power-up, or the Windows error message telling me "the gyro has failed to initialise", that my previous unit did.

However, it's likely these two (now resolved) issues are unconnected to my main 'browning out' problem anyway and without concrete proof as to what has-been/is going on, I'm currently lacking to balls to fire her up.

Right now, I'm pinning all my hopes on Skookum finding a hairline cracked joint or track in my original SK-720, but I doubt this will be the case.

[Windbreaker]

You might want to go through your entire wiring harness to make sure all the connectors are clean and secure, and that there are no chafed wires.

Good luck with the testing.

I just got an SK720 and have gotten great results.

[Helos4me]

Ian, get some balls and make some reasonably long chicken sticks and zip tie them to the skids. That way if it tips you'll have some time to react. I did that with the sk 360 when it first came out and I was very new to fbl. After one hover check I took them off. The old ounce of prevention, worth a pound of cure idea.

[Ian Davidson]

I've already had to resort to using over-sized training gear and it certainly saved my ass! Please see the 4th picture in my opening post.

https://www.helifreak.com/showpost.p...71&postcount=1

You right though, I do need to get some balls. I'm going to pluck up the courage and give it another test-flight very soon, but I was kind of hoping to get some feedback from Skookum as to whether they found anything suspicious with my original (and now returned) SK-720 before this.