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JVC KM-1200 help
MUFF WIGGLER Forum Index -> Video Synthesis Goto page 1, 2  Next [all]
Author JVC KM-1200 help
Hi guys I just picked up a JVC KM-1200 SEG/mixer for super cheep (£30)
mostly bought it as a useful source of black burst and sync signals but it would be cool to use its chromakey and mixing capabilities

and I'm finding setup a bit perplexing meh

I am used to the super simple internal tbc panasonic mixers but this beast has got me scratching my head, I have the manual here in front of me but

the mixer has two modes internal sync and external genlock
I assume I need cameras with external sync inputs? (which I can easily get) but the manual is pretty cryptic on how these would be hooked up without using large broadcast cameras with ccu

is there any way to get a signal out of the KM-1200 without inputing anything just to test its output (so far I haven't got even a scrambled image using a un sync'd black and white cam)

also any tech info on the severed heads video synth The SuperNova 12 which uses this SEG as its sync provider would be greatly welcomed as I will hopefully be building some video oscillators for a similar system with Richard if he has time to lend me a hand

basically I'm asking what's the bare minimum i need to get an input/output going

thanks for any help guys
Jeffrey Siedler is the man you want to talk to.
He's the owner of the Supernova12, and would be more than happy to discuss this unit with you. I'll pm you his email address.
I've never seen a KM-1200 before, but I found some pictures of one, so...

On the back there is a switch for "color" on input #5. With that switch set to color, the SEG on internal sync, the input buttons on the three input buses pressed for "5/Color", and the rotary switch marked "Color" set to a color, you should get a solid field of color on the program and preview outputs.

I don't see a switch to enable/disable the Genlock (I'm sure that's explained in the manual). With a stable video signal plugged into the genlock input and the "5/Color" switch on the back set to "5", and the input buses all having "5" pressed, you should get that image on the program and preview outputs. For a stable image to genlock to try a DVD player or broadcast TV (or cable TV box). Don't use something like a VHS deck until after you've seen it work with stable video.

When doing these tests turn off the DSK (Down Stream Keyer), the Chroma Keyer, and Auto-Take.
Oh, and turn all the 75 ohm Off/On switches on the back to "On".

If you have a scope you should be able to see sync signals coming out of the sync outputs on the back.
thanks Dave and Johnny

especially Dave thats exactly what I needed to hear
will try and report back
ok not getting a colour output

will brake out the oscilloscope
Try all three outputs (Preview and both Programs.

Are the lights lighting up? If not, unplug it and look for a fuse.

Is that a trap door on the bottom? If so, maybe something inside is not seated in it's connector. I know the Panasonic SEG that is similar to this has had issues with boards that plug into a mother board and sometimes one comes loose. (don't explore the inside unless the unit is unplugged)
tried all the outputs
lights are all good

will have a peek inside (i was gonna when it arrived but chickened out )

i am aware of the dangers of high voltage stuff and will do it unplugged and with great care

one other thing could it be the cheap tft im using as a monitor is the problem its always been ok with other old gear?
Most cheap TFTs can handle video fine, and many are even multi-format. Though if the TFT is PAL only and the SEG is NTSC, you won't see color.

The scope should tell you if there's a signal or not.

Does the manual explain how to switch between genlock and internal sync?
I popped open the back on its hinges the construction is very neat and nothing seems loose as far as I can see

to switch from gen to internal as you guessed you use the switch at output 5 and it involves the configuration other equipment being used

the seg is PAL and I don't even get any visible signal of any kind

I lent my scope probes to somone who moved away cry but I will report back as soon as I can jerry rig some or buy some new ones

thanks again for the time out of your day dave it has been really helpful
thumbs up
Hook up a BNC cable directly from the SEG out to the scope input. It won't be perfect, but you should see something. Even better if you have a BNC "T" adapter and a terminator to stick on the end at the scope. Try all the outs, including the sync outputs to see if anything is putting something out. (the Sync, HD, and VD ones are probably 4 volts p-p while the BB one is going to be 0.3 volts)

If you don't have a BNC cable, how about an RCA cable with two RCA to BNC adapters? You could even use an RCA "Y" adapter to get the signal into the monitor and the scope at the same time. That would let the monitor provide the termination.

You don't need precision at this point. You just need to see if there's any signal at all. If it looks like black burst on the outputs, that would explain why the monitor is blank as much as if there was no signal at all.
I have the KM-1200. Dave is right. You should get a color field out of input 5 even if the switch is set to genlock if you have no signal connected. If you push 5 on input A _ B and Preview and hit auto take you should have the color field. Make sure to turn the COLOR knob away from black though.
If this does not work something is wrong.
just a quick update guys

I scoped the outputs and It seems to be putting out a sable sync signal on the sync output and the bnc next to that marked hd/bl puts out sync

but none of the other outputs produce a signal

I'm going to pop it open again and test and look for loose connectors

FML cry

anyway ill report back more after I get time to try

edit had a poke around I now get a few dim green lines when I switch on while connected to the preview output cry cry
If poking around made a change, then it sounds like something is not making a good connection.

Possible trouble shooting tips:

- If you spot any chips in sockets, push down on them. This will often break a thin oxide barrier that can build up between a chip and socket.

- if any of the boards are plugged into another board (typically with edge connectors) try removing the board and pushing it back in. Maybe a couple of times. Same oxide issue, basically the same solution as the chips/sockets.

- If there are cables plugged in with connectors, try unplugging them and plugging them back in a couple of times. (same oxide issue/solution)

The fact that you have sync coming out means that some part of the unit is working. The question becomes is the rest not working due to damaged parts or is it simply a bad connection somewhere.
well I cant tell if it was a change or not as i didn't perform the same action before the poking

I also tried moving the tiny sub boards with edge connecters and couldn't shift them, moving the larger connectors between boards was fine but all the flying cables seem to have very delicate connectors so I was hesitant to fool with them

it reminds me of working on a juno 106 i fixed for a friend

maybe this is one for the scrap heap
Just got a second one for a similarly low price so we will see if it works or I was miss-diagnosing the problem This is fun!
so the second unit seems to work in a similar way and I am not getting any colour output with nothing connected

very curios

I will solve this!
Do you have an oscilloscope or waveform monitor to look at the output signal to see if it has burst and/or chroma in the video part of the signal?
daverj wrote:
Do you have an oscilloscope or waveform monitor to look at the output signal to see if it has burst and/or chroma in the video part of the signal?

yes Dave but by colour output I meant a plain colour field like I couldn't get before (so just to be clear this new unit acts exactly as the previous one no output except sync as far as I can see)

as instructed by your very kind and patient advice before I looked at the outputs on my scope and could only get the sync output to produce a signal on the screen

I think I am just missing something obvious in plain view d'oh!

maybe I need to provide it with a clean genlock signal or something from outside to make it play nice any way I have now contacted Jeff to see If he can shed any light on the issue

I am sure I am just being stupid as per usual meh
The 5/color output should give you color out without anything connected (the video input 5 selector between color/genlock switch to color if no video is present at the genlock input). The color rotary switch should be set to one of the colors and not black. Could it be a PAL/NTSC issue?
thanks don't think it's PAL NTSC issue as I would get some kind of image at the output

so your coming out of the which output PREVIEW or PGM ?

could this be a cable issue I am using bnc/phono adaptors and phono cables ?

EDIT ok just did a caveman type test put a signal through the mixer and then out to a monitor nothing showed as usual until I powered down and then back up

for a second I get the image and then it cuts out (could this be a cable/grounding issue)
It does not matter if you go program or preview out. Never use audio cables for video. Video cables should have 75ohm impedance.
kjellb wrote:
It does not matter if you go program or preview out. Never use audio cables for video. Video cables should have 75ohm impedance.

I think it might be time to make some proper BNC calbes

luckily my work has some crimps and materials its ok for me to use Mr. Green
If you find phono cables with yellow marked connectors they are video cables.
kjellb wrote:
If you find phono cables with yellow marked connectors they are video cables.

well I'm using a mixture but for the test I used a video cable and it still cut out

I'm betting this is some kind of grounding issue
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