Kortek KT-2914 Yoke testing

[antony30bc]

I had an issue with my Kortek monitor a while back where the power was on as the green light on the user control board was activated but I received no video signal and heard a clicking noise.

Betson offered to replace the main board and the neck board if I sent them in , so I did. Well while they were being repaired/replaced I donated the PC in my mame cabinet to a couple I know in NO who lost their belongings in Katrina. I got my monitor boards back but did not have a PC to go back in the arcade so left them in the shipping box for about 6 months.

Last night I finally replaced my PC, and decided to reassemble the monitor. I hooked everything back up how it was (per my diagrams when I removed the boards), powered the monitor on and I got an intense hissing noise and the screen was not showing a picture. I unplugged the unit, reverified my connections, and tried again. I got the same results so unplugged again. I decided to give it one more try but on the third try I did not even get a power up.

I called Betson and they told me that the yoke may be frying the boards/power supply and even if they fix the board it will likely get fried again. They suggested I have the yoke tested for resistance and that it should be 3.2 ohms on once side and .5 ohms on the other. I have a multimeter and feel I could check this, however I am not sure where on the coil they want me to check.

Any input would be appreciated.

Stephen Goldberg

[grantspain]

what they are asking you to do is check the resistance of each pair of wires from your scan coils,obviously you know the scan coils/yoke is the bronze looking coil on the neck of your tube which has four wires going from it to the chassis sometimes on one plug,sometimes on two-you should be looking for red/blue one pair yellow/green the other,you should unplug each plug at a time and meter resistance between those two wires.BUT hissing usually denotes a broken tube or ht arcing(or sometimes a cap ready to go)-you should look at the tube neck area when you switch on to see if you have any blue sparking going on before you do anything,I personally have never had scan coils go short-but thats not to say it could happen its just very unlikely

[antony30bc]

Thanks for the advice. My hand held analog multimeter sucks , it only has one resitance setting which is 1k Ohms and I am expecting values between between 3 and .5 ohms.

I will pick up a cheap digital multimeter tommorow to measure this. I don't think it is the coil either. The plug coming from the coil to the main board with the 4 wires has them all connected on a single plastic terminal so I unplugged all 4 at the same time. Will this cause a problem in the measurement?

I did not see any sparking when the hissing was occuring as I was under the desk plugging it in. At this point I am certain the power supply blew from whatever the issue was. Betson doesnt want to repair the boards till I test the coil though as he suspected that is what blew the power supply.

If a cap blew is this something I would visibly see?

Stephen Goldberg

[grantspain]

if a cap blew then you would have lots paper looking debris around the chassis(if its an electrolitic that is),i guess betson are trying to see if you plugged all connections in correctly,that meter you have should suffice-did you say you had a hissing or a high pitched whistle.you should measure the scan coils with the plug disconnected because its on that plug that you can get to wires to measure them easily,just NEVER switch your monitor on with the scan coils disconnected.

[antony30bc]

Well the old multimeter was really a piece of crap. I went ahead and got a 30 dollar digital one and it worked beautifully. In fact measuring the blue/red showed about .4 ohms, and the green/yellow showed 3 ohms. The exact resistance the Betson tech told me there should be.

I will call them again and see about sending the board in. One thing I noticed, I diagramed the cables before I dissasembled the boards. When I sent both boards in the Betson Tech reattached the cables between the neckboard and the main board. The Red, Green, Blue plug that goes from the neck board to the main board was plugged into a different plug on the main board than when I dissasembled. There are two plugs on the front left of the main board

The black rectangle shows where the cable was plugged in according to my diagram. The blue rectangle shows where it was plugged in upon receiving both boards back from Betson.

Stephen Goldberg

[grantspain]

perhaps that is just a frequency plug,sorry cant say for certain i am not familiar with that chassis.

[brandon]

perhaps that is just a frequency plug,sorry cant say for certain i am not familiar with that chassis.

I just bought one of these monitors myself, I'll go out in the garage and see how its connected.   in the meantime.. here ya go.. this is a diagram straight out of the service manual. 

EDIT:  I noticed this thread and it made me think.. http://forum.arcadecontrols.com/index.php?topic=50927.0

maybe you have the same problem?   Perhaps the board just blew a fuse.  If so, and you can easily replace it you could try powering of the monitor briefly in low light so you can see what is arcing.  I wouldn't recommend running it for very long like that though.

[antony30bc]

Thanks for the Diagram. I thought I had the service manual but I couldnt find a diagram that nice and clear.  Where it should have labels all I could see were little dots.

From looking at the picture it seems pretty clear my diagram was wrong and that the service tech did hook the RGB cable to the right plug. There must be something else goofy.

I will call Betson tommorow to let them know the outcome of the resistance testing, and see what next steps the offered me.

Stephen Goldberg

[grantspain]

judging from the diagram you wont do any damage with this plug

[antony30bc]

Aye looked closer its just CGA vs VGA right.

Shintzu

[brandon]

thats sort of weird that one would say CGA and one VGA.. I mean, by default it should do either or anyways.. mine does..  Maybe they use this same chasis for a few different models that have to be set manually...     I'm not the person to ask when it come to monitors