Syncronization of line lock

[cctv_down_under 0]

OK OK, so I always used 12V for my jobs so never had to worry about it.. I have a problem

 

I have a standalone machine that has a secondary monitor output that is sequencing, the idiots fed this into two x 1 in 8 out distributors (does not appear to be amps) to get 15 monitor outputs, some of the montiors have a roll in the picture when rotating which i assume is a sync problem but I am not sure.. it seems it could be one of three things.

 

1/ The switching on the spot monitor is set too fast and the distributors when recieveing the switch are not keeping up

 

2/Syncronisation needs to be done to line lock the cameras.

 

3/ A weak signal is present.

 

I am not sure how syncronisation works with line lock and would have thought that the DVR would compensate for this and that if it was fine on the DVR it must be fine on the monitors...is this correct.. and if not how does sync work, i understand the priciple of the sine wave but how is it set up to be adjusted...do you flick a switch, must power be run in a series, how does it work..

 

The DVR is a Divar and the cameras are 24V powered Dinion XF's

 

 

Thanks in advance guys.

[rory 0]

havent had to do this myself, but from what I read, you just set all the cameras to line lock mode. Maybe someone like AV can jump in on this one ..

[AVCONSULTING 0]

This is a pretty complicated situation. First problem - Are they taking the switched output from the DVR and splitting it to the DA's by using a T connector? If so this is not good since you are now dividing the impedance by 2 and that alone could be a problem. If so then a possible solution would be to first feed the switched out to only one DA, you will get 8 outputs. Take 7 of those outputs to monitors and take the 8th output to the second DA where you will then get another 8 outputs or a total of 15. From your initial description this sounds like what they are doing but wanted to cover that just in case.

 

Second problem is your camera sync. The cameras are most likely out of sync and depending on the camera you may or may not be able to put them in sync. First you have to find if there is a phase adjustment on the camera. Second you have to make sure that all the cameras are being fed with the same phase from the power supply. Is this a multi output power supply or are there multiple supplies? Either way you have to feed all the cameras the same. Think of it as plus and minus even though it is 24vac. If your power cable has a ridge or color then make sure you feed each camera's power with the same side, otherwise you will have cameras 180 deg out of phase. Once you have made sure all cameras are being powered correctly and if you still have a phasing problem then you need to fine tune the phasing or sync.

 

To do it the right way you need a sync meter but they are not easy to find so a quick and dirty method is to take a t connector and a monitor and take one camera as the master. Take the master camera and another camera, take the outputs of each camera into the T and then out of the T into the monitor. You'll get two pictures overlapping but if they are out of phase then one picture will be rolling or out of phase. Turn the phase adjustment on the non master camera until it stabilizes. Then take another camera using the same original master and repeat. Keep doing this until all are in phase. Hopefully then all will be in phase and your rolling will stop. This isn't perfect and may not work but it is the best you can do. Picture flipping on a switcher is pretty common and that is one of the reasons switchers got replaced by quads and then by multiplexers.

 

Hope that helps somewhat, good luck.

[Cooperman 0]

Good advice AV

 

A couple of thoughts to add. Whilst the line lock / phasing issue may be a contributory factor, I'm not convinced that more fundamental problems may not be to blame.

 

DVR Expert, perhaps if you try a few tests just to get a better feel for what's going on.

 

Firstly, I'm assuming that all monitors are displaying the same signal, so if the distributors are not amplified, any signal degredation through cable runs, signal splitting etc., will become progressively worse as a result. Is the problem more obvious on the furthest monitors (longest cable runs), or are they all doing the same thing at the same time?

 

If you can use a decent test monitor in place of one (or more) of the 'rolling' monitors, see if you have the same problem. If so, take the test monitor back to the output from the distributor and check again. Perhaps isolate one distributor, and see if the 7 remaining monitors are working o.k. (or better).

Check the switched output from the Divar - it should be spot on (if you'll pardon the pun). If it is, try connecting one of the furthest rolling monitors directly to the switched output and see if the problem disappears.

 

If you can lay your hands on a dual beam oscilloscope, you could actually see what is going in and coming out of the distributor (if you want to borrow mine ).

 

Anyway, if it was a simple 'line lock' variance, I would expect a quick roll in the picture before the monitor locks on to the signal. If it is rolling a number of times, this may suggest either a heavily attenuated signal (either through length or quality of cable runs, or lack of amplification in the Video Distributor) or possibly even a monitor in need of an internal tweak on the vertical hold.

 

My best guess at the moment is either they need a couple of decent VDA's, or the monitors are not playing the game.

[Thomas 0]

If you're loaning out that oscilloscope........

[Cooperman 0]

Anytime, but you'll have to be gentle with it Thomas, it's an antique Tektronix.