Ch 7, Camera Pan gone wrong - Now SOLVED - for certain !!

[wgt40w]

Everything WAS working OK.

Futaba FP-T8UP tx + EZUHF. Channel 7 on Rx controls camera Pan (just removed Tilt servo).

Ch 7 is set to be controlled by the CH7 'pot' on the tx.

Problem:I switch on Tx + UHF, then when I switch on the plane, the camera servo immediately slams round to full lock (to the left). The 'pot' on the tx does nothing.

1) I have disconnected the pan servo from the rx and connected to a servo tester - all working ok.
2) Due to previous experiments trying to setup a Head Tracker (unsatisfactorily), I have checked in the tx menu that 'Trainer' is INH with Ch 7 & 8 'off'.

I'm sure the problem is something 'silly', but I'm damned if I can think of the solution.

Any suggestions, please.

UPDATE:

I thought I had solved this problem, but now discovered what the problem is:-

Using Immersion Vtx, have recently upgraded from a 5v camera to a 12v one. Am using a 12v step up regulator between the vtx & the camera.
Thing is - IF I leave the vtx to camera wire DISCONNECTED - the camera pan servo on Ch 7 (or Ch 8) works perfectly.
BUT - as soon as I connect the vtx to camera wire the Pan servo immediately goes to full lock and will not answer to radio tx control.

I have the vtx to cam wire taped together with the pan servo wire - I wonder if now that the camera voltage has been stepped up to 12v (from 5v) this is causing interference to the servo wire ??

[wgt40w]

Added this to 'bump' thread up from bottom of list

[BigMouse]

Noisy step-up-reg sounds prime suspect to me!

Try easiest things first!
Obvious first step is to separate the two wires
and/or add a Ferrite ring on pan servo lead (try near servo end first, then near rx end)
and/or try a low pass filter on the reg output supply.

One or a combination should work...

[wgt40w]

Bigmouse - thks for your input - think I have solved it myself.

The new 12v camera has a 5 pin wiring socket on the rear. The 5 to 12v step up regulator wiring has a 3 pin plug on the end. At the time of purchase I asked how to fit 3 into 5 and was told to fit the 3 to the LEFT end of the socket - which I did and all worked OK.
Last night I removed the camera to work on something else and think that when I replaced  the cam I fitted it upside down so the left end of the 5 pin socket became the right end - if you see what I mean ! Have now moved the 3 pin plug and all OK !!

[wgt40w]

Well I thought I had this sorted - but I haven't.

Starting from the vtx, which is supplied by full 11.1v 3s, 5v is output to EZOSD - the 5v 'passes' through the osd and then goes through a 12v step up to the camera.

I have now found:-
IF the power supply to the vtx is DISCONNECTED - plugging the osd to cam wire in STILL causes the pan servo on ch7 to lock on full left lock.
I am wondering if I have some sort of earth loop problem, but cannot understand why it is only the pan servo that has a problem and all the other servos are OK ?

This got me thinking and I have just tried another servo - Hey Presto - all problems seem to have gone !

I still am baffled as to why a servo works perfectly when plugged into a servo tester, yet goes berserk when a camera wire is plugged in with no elec supply.

Oh well, it's currently thundering down with rain and this problem is keeping me occupied !!

[Coyote]

Oh I have this before, took me an age to find out what it was.

Do a quick test for me, unscrew the pan servo arm srew that locks the arm to the servo. Does it not work fine ?

The put the screw back in, but unplug the camera at the camera end. Does it work fine again now ?

[wgt40w]

Coyote

Thanks for an, as ever, very interesting reply. How on earth did you ever discover that?

Anyway, in my case, the problem was the pan servo itself - one of those small, nasty, cheap, Chinese plastic geared ones. I have changed the servo for another (same type, hadn't got anything else) and all is fine again. Will try the servo again, when I have calmed down, with the servo horn screw removed.
I assume you are suggesting that the horn screw can go in too far and short the servo internal pcb ??

[Coyote]

Its the camera`s inside, the circuits touches the cameras case, the case is screwed to the bracket, the metal bracket is screwed with a metal screw to the servo and that makes the link electrically from the camera to the inside of the servo. 

I descovered it when it would work fine off the bracket or with the camera cables not connected. I wondered if it was rf related, but even in close proximity, as long as there was a break ( electrically ) from camera to servo screw it was fine

What I did was drill the hole that the servo screw goes through on the bracket so it does not touch the metal, problem solved, it stopped altogether :)

You could also try a shorter screw but then you loose strength

[wgt40w]

Yes Coyote everything you say did apply to me - If I disconnected the camera wire all was ok, but even with no power to either the vtx or the osd, connecting the camera caused the problem to occur - this is why in one of the above posts I wondered if I had some sort of earth loop. Yet I couldn't understand why the problem suddenly happened when all I had done was take things apart and put them back together again !

In a way I'm glad this has happened, as, if it had happened whilst in the air, for me it would have been a major problem trying to pilot a plane whilst looking 90 degs to the left ! (Accepting my vision isn't great whilst flying LOS)