Kortek Monitors Tips,Tricks and Cap Kits

[cadillacman]

So far, an epic fail for me.

Changed r206. r207. Verified my replacements meter dead nuts on.

Changed the vert ic. Insulator came off in one piece so i reused it.

Changed all caps anywhere near the vertical section. Also replaced both 1000uf caps in the power supply section.

Same issue. Tries to power up can hear hv squeal, then shuts down. Never any neck glow. led on remote bd. blinks on/off while this is happening. After a few mins the led just stays on and no other signs of life.

I believe you about the vertical ic being an issue, but apparently thats not all that i have going on unfortunately. I tried just the resistors, well, because im cheap and impatient hehe.

i guess my next step is to proceed to finish the capkit.

EDIT did full capkit(less the 3 large filter caps c114,711,130 that wernt in the kit) and found more questionable traces i repaired and even a few cold solder joints on the neckboard.

Still nada, same issue. Im kind of mad at myself at this point, i was really hoping i would be able to save this monitor. OHMERONE man, really, i sincerly thank you for helping me this far. I can say at least i tried. But im not ready to give up yet if you arent.

EDIT AGAIN found c138, c302, c125 in backwards. WTF is wrong with me.. thats what happens when youre doing a capkit while in back pain and a 4 year old continously dirtracting you lol.. will switch those around and see if i get lucky...NOPE of course not.

I did repull the insulator around the vertical ic and it still looks ok but i went ahead and flipped it around and reinstalled.


DO you happen to know what yoke ohm readings i should get? id like to verify my yoke isnt toasted.

to BE CLEAR IT CYCLES POWER slowly several times accompanied by some sort of hv hiss, then after a minuite or so it goes to bliking the led fast and sounds like a neotec chassis does when the hot shorts, that fast power cycling and chirp kind of

Even though i cannot find a short in the hot, i wonder if i should try replacing it anyways?

 

[Level42]

@Ohmerome => Any chance you have the manual/schematics for a Kortek KFM-20 and KTN-20 ?

 

[Ohmerone]

More Tips and how to test a Mosfet.

So far, an epic fail for me.

Changed r206. r207. Verified my replacements meter dead nuts on.

Changed the vert ic. Insulator came off in one piece so i reused it.

Changed all caps anywhere near the vertical section. Also replaced both 1000uf caps in the power supply section.

Same issue. Tries to power up can hear hv squeal, then shuts down. Never any neck glow. led on remote bd. blinks on/off while this is happening. After a few mins the led just stays on and no other signs of life.

I believe you about the vertical ic being an issue, but apparently thats not all that i have going on unfortunately. I tried just the resistors, well, because im cheap and impatient hehe.

i guess my next step is to proceed to finish the capkit.

EDIT did full capkit(less the 3 large filter caps c114,711,130 that wernt in the kit) and found more questionable traces i repaired and even a few cold solder joints on the neckboard.

Still nada, same issue. Im kind of mad at myself at this point, i was really hoping i would be able to save this monitor. OHMERONE man, really, i sincerly thank you for helping me this far. I can say at least i tried. But im not ready to give up yet if you arent.

EDIT AGAIN found c138, c302, c125 in backwards. WTF is wrong with me.. thats what happens when youre doing a capkit while in back pain and a 4 year old continously dirtracting you lol.. will switch those around and see if i get lucky...NOPE of course not.

I did repull the insulator around the vertical ic and it still looks ok but i went ahead and flipped it around and reinstalled.


DO you happen to know what yoke ohm readings i should get? id like to verify my yoke isnt toasted.

to BE CLEAR IT CYCLES POWER slowly several times accompanied by some sort of hv hiss, then after a minuite or so it goes to bliking the led fast and sounds like a neotec chassis does when the hot shorts, that fast power cycling and chirp kind of

Even though i cannot find a short in the hot, i wonder if i should try replacing it anyways?

I would not suspect the Yoke...even if there was an loose plug
or whatever the yoke plug connector was..
Just post your ohms and we can see if it is right..
Most issues with yoke you can see the burned windings if you take it off the tube and look.

It does seem you have other issues here and need to go to other circuits..
after you restore the vertical issue.
I'm going by common problems not odd balls here...

I normally replace the caps if they haven't been replaced before,,but you might
target these parts first..
Keep in mind when there is a short on any vertical circuit you can remove the part
and take away the load on the power supply because it doesnt take vertical
deflection to get HV or raster..during test chassis..

This is not the chassis to be installing the parts in wrong,,smile


The squeal is part of a audible symptom you can get from the T303 and HOT
Where it seems theres some Hv or not quite get up..or shuts down
and no Mosfets tests shorted or there is no HOT short C to E..

The target parts are T303 and HOT..c724
when c724 fails it saturates the HOT incases like this you will find
a short between Base and emitter and is a clue this is why..Because
most if not all NPN transistors short Collector to emitter..
and there no issue with the drive gong to the base..

Ok now I normally replace these parts i dont look for 10 good reason to do it..
Because the symptom vary each repair,so its a no brainer to just sub these
parts out because they are a known problem..
But there are visual symptoms and thats the wraping of the T303 may look dark
compared to others around it of that type..
Another they do fail and I replace the T303 and Hot with upgrade trans and the coil
The coil is different and my not be needed to go further here..
But you need to replace the transistor with upgrade,,,because it can fail
because this cap in the Horizontal drive circuit c724..

I have asked for these parts from casino tech and they say NLA
So tips without all of the parts are The HOT upgrade and the cap!
Leave out the coil and t303 because you can't get it..anyway or from a used
chassis with the same markings on thier case. It is or will be bad.
And can cause a chassis not to be repaired

Ofcoarse you need to check the mosfets I mentioned anyone can fail
and cause a shutdown issue.
When mosfet is out of the chassis..
I recommend you use a anti static pad often found
come with a new part,,this way the parts stays still and static free
and incase the is a static issue it can damage the part
but rare when test from my experience...

To test a Mosfet is different then a transistor.
You need the Ohm meter Only to test each junction..
U can use a datasheet from mouser to see which pins are what..

A gate pin would be like a Base pin compared to a NPN transistor
A Drain pin can be like a collector compared to a NPN transitor
A source Pin can be like a Emitter Pin compared to a NPN Transistor.
You can remember the pin config by using the Phrase
Gate or Good
Drain or Damn
Source Or Stuff
"Good Damn Stuff"
So with the Mosfet laying down it would be
Left pin is Gate, middle pin is Drain, the last pin would be Source..

Just a way ..
To remember the configuration or basing..of the mosfet..
Keep in mind that a short transistor reads shorted just like short
your ohmer there would be zero ohms..
Of coarse a good Mosfet has high ohms across each junction.

Tip some chassis will use the same parts in another circuit not related
to that circuit so as a comparsion you can compare your ohm reading to a
questionable part...as always its best to remove the part but can take atleast
on leg open,or remove solder from the pin and then test each junction
from Source to gate and drain they are a 3 pin transistor but your not measuring a
diode here so dont use the diode checking..
They are easy to trigger a mosfet and be miss leading...if its bad..
Same cases the mosfet blows up so its obvious if you just look at it good..

Here are some tips on checking a mosfet transistor ,it is a from the transistor family..


Nowadays most multimeters have a diode test range. On most multimeters (but by no means all!) this puts about

3-4v across the device under test. This is enough to turn on most MOSFETs - at least partially, and enough to

test. The meters which use a lower open-circuit test voltage (sometimes 1.5v) will not make this test!

Set one of the meter's probes to the MOSFET's drain lead and the other probe to the source lead. Read the resistance on the meter's display.
Reverse the probes and read the resistance.
Both ways, you should read infinite resistance.

Touch the meter's red or positive probe to the MOSFET's gate lead.
Touch the black or negative probe to the drain lead and note the resistance reading.
Touch the black probe to the source lead. Both readings should
indicate infinite resistance.

Set the black probe on the gate lead. Touch the red probe to the source lead and note the resistance.
Touch the red probe to the drain lead and read resistance on the meter's display.
Both readings should indicate infinite resistance.
If the device fails any of these tests, replace it.


To Level42 have you check Happ for the schematic?

 

[AlucardXP]

This is great. I just got a cabinet with a kortek 2914f in it. When I first powered it up, it had a rolled image. I pulled the chassis out to find a burned mosfet (19n20...cant remember the location without looking at the chassis). I replaced it with a IRF640 that I had laying around, and the monitor fired up and looked great. Of course when I shut it to put button it all up, it made the infamous clicking when I fired it back up. I havent tested everything but on a diode test, I know the HOT is shorted at pin 1 and 3. I havent pulled it yet to keep testing.

What replacements can I use for the HOT?

 

[cadillacman]

did some poking around...

q603 is shorted across the outside terminals. pulled and verified.

Need to lookup a data sheet, this may be normal for this type of n channel mosfet.


my yoke meters out at"
red/blue= 1.1 ohms
green/yel= 3.2 ohms

Hot still doesent check shorted. I think i may replace it anyways. The transformer(t103) does not look burnt, but it a litle more brown/discolored than the rest.

 

[Ohmerone]

This is great. I just got a cabinet with a kortek 2914f in it. When I first powered it up, it had a rolled image. I pulled the chassis out to find a burned mosfet (19n20...cant remember the location without looking at the chassis). I replaced it with a IRF640 that I had laying around, and the monitor fired up and looked great. Of course when I shut it to put button it all up, it made the infamous clicking when I fired it back up. I havent tested everything but on a diode test, I know the HOT is shorted at pin 1 and 3. I havent pulled it yet to keep testing.

What replacements can I use for the HOT?

Ok, You replaced a scan Mosfet and replaced it with the not so perfect sub
check the spec's it won't last..

Its important to understand each component and what it needs not what you like to
do with it...A Mosfet shorts between Drain and Gate..orsource to gate
meaning that when it does
it sends a larger amount of dc to the gate which is always the drive trans or circuit..
Meaning that the switch driver trans gets part of the excessive current and needs
to be replaced..Im using a sniper gun not a shotgun here...

I dont replace parts that way..I look at them in detail and the nature of the beast
how different chassis are and the way the company made them along with
skill and knowledge not a guessing game to me..

I tell you to do something you just do it..
This Repair Log is not about what I tryed and it didnt fix it..
Its about Facts and what i replaced to fix the monitor and keep repaired!!

Yield my warning's and get the chassis fixed right..

The Hot fails and needs to be replaced again it does not always
short collector to emitter is the chassis Its more of Base to emitter
because of the the driver circuit not be right..

A short Collector to emitter would indicate something different here
and would need different parts..

Get the upgrade noted on the first post#1
Again check each part again and get your parts list together
and then order them...Caps need to be replaced..if never been replaced before
unless you have a good skill set and can detail each circuit then target each cap
if you like..just remember they are all the same age and could fail any minute
I dont make a big deal out of the Big filter cap and it doesn't come with every
cap kit but needs to be checked, in most cases i cost alot so I look for symptoms
from it before I replace it and I will mention it when I suspect it should be a part
of the cap kit..
Now the cap kit includes the vert-Ic and the resistor's
and HOT upgrade and the scan transformer and coil if available

The scan transformer t303 is mainly for no Horizontal deflection.
and the coil. not no High voltage...I just talk about them as a whole
replacement list of parts to be replaced thats all..

And stock the Scan transistors and driver atleast one for stock..
If there is a kit anyone uses I want to know changes have been made
or any parts that was found in the chassis but not in the kit?

If anyone needs help reading the schematic ask for help its like a road map
you have to find the common areas and work from there..
Not all schematics offer voltages some do check the schematic
Remember most if not all caps are riding the supply voltages that we are installing
so you could cause a problem by installing them the wrong way..

Don't use you memory use good notes pictures,ect..dont make it worse
then it was...Be a thinker thats what you pay others for so use your head!!

 

[Ohmerone]

did some poking around...

q603 is shorted across the outside terminals. pulled and verified.

Need to lookup a data sheet, this may be normal for this type of n channel mosfet.


my yoke meters out at"
red/blue= 1.1 ohms
green/yel= 3.2 ohms

Hot still doesent check shorted. I think i may replace it anyways. The transformer(t103) does not look burnt, but it a litle more brown/discolored than the rest.

I posted on how to check a mosfet check the procedures..
with Q603..

If you need to try some more ideas
Lets Lift L601 to remove any voltage to the flyback
and see how the chassis reacts to this..
If there is a issue on that line then the others should settle down..
and you can monitor the power supply voltages.

I suggest the HOT get replace no matter what with the upgrade..!!

The yoke readings are within range...for the 2914 yoke

 

[cadillacman]

Thanks for the help so far man. For now, i think this monitor is going to go on a shelf. If anyone needs a nice tube or parts chassis lmk.

 

[cadillacman]

well.. i am a glutton for punishment... picked up three more 2914 chassis.

Chassis #1 appears to already have had the vertical issue stuff fixed. I found ic105 had completely fallen off of the chassis. DOes not look like it got hot and unsoldered itself, rather it looks like it was barely soldered on from the factory and fell off. Other then that, i reflowed tons of bad solder joints all over the place. Going to test this chassis in an hour or so and report back.

Chassis #2 and #3 have fried resistors near the vertical ic and i will test those to see if either have any signs of life. If they do(hoping they just ave vertical collapse) i will change the resistors, ics, and recheck.

Once i have a working monitor i will be happy, and should have plenty of parts leftover for whatever.

 

[cadillacman]

just frickin shoot me..

Chassis #1 in.. powers up, then lightning sound. I get a wicked awesome lightning storm inside the neck by the guns!!!!!!

i am pretty damn sure i have all my grounds hooked up but i guess i will recheck the manual to make sure.

Tubs looks perfect, even still has the plastic protector on the neck pins/socket. BUt it sure acts like a tube that lost vacuum... this blows.

 

[Ohmerone]

Hey Whats up..

Do you only have one tube your checking these chassis on?

Find any shorted mosfets and are you replacing the HOT with

the upgrade Transistor..its best to just replace it dont just test it for a short..

If you have a issue with the vertical circuit and no high voltage

then you can remove the vertical Ic and just work with the HV

and get it going first and back to the vertical circuit..

Take your time look it over good..

 

[cadillacman]

yeah i only have one tube and yoke...

I tested it with my bk470, tube is toast. I set the heater, i see no heater.

I get no output from the guns even if the gains are all the way out.

DOnt know if something inside shorted or what, when this thing is powered on i get sparks all around the metal cage surrounding the guns inside the tube neck..

I really wish i would have tested the tube before i went through all this effort.

I guess im on the hunt for a old 29" crt tv now lol

 

[Ohmerone]

yeah i only have one tube and yoke...

I tested it with my bk470, tube is toast. I set the heater, i see no heater.

I get no output from the guns even if the gains are all the way out.

DOnt know if something inside shorted or what, when this thing is powered on i get sparks all around the metal cage surrounding the guns inside the tube neck..

I really wish i would have tested the tube before i went through all this effort.

I guess im on the hunt for a old 29" crt tv now lol

Might mark that chassis and use a glass jar to put the HV anode in, next time

and measure the HV first ..before hooking to another tube..

Whats the tube Number#

 

[cadillacman]

verified tube.

Hooked this chassis up to a 25" tv tube with a nanao dual res yoke( a litthe higher but close readings) and it produces a picture, no lightning storm.

WHen this chassis is hooked up to my laptops video out, all i get is a quick pic then it goes away, this repeats every 1-2 seconds. I dont know if that means the video section of this chassis needs recapped or if the monitor simply does not like the signal from my laptop.

Its progress i suppose.... just not quite what i had in mind lol.

So.. i guess i need to hope i can find a 29" tv tube somewhere cheap.

samsung tube# is a68qb892x

 

[retrogamez]

Hey Ohmerone,
Can you give link on where to get the upgraded HOT. I tried googling the number you posted and get nothing. I have a KT-2938 that had a dim screen so I replaced c118. Hooked it backup and now have horizontal collapse. HOT didn't show short while in chasis so I went ahead and orderd a cap kit and replaced all caps. I now have a thin quater inch vertical line for a picture but its super bright. lol I'll be pulling and testing the HOT and two mosfets you listed tonight but even if my HOT is good I'd like to order a spared just in case.

I appriciate all your input on the forums. You've helped me repair many of my monitors without me even having to ask any questions due to your detailed responses to others questions.

Thanks

 

[Ohmerone]

Hey Ohmerone,
Can you give link on where to get the upgraded HOT. I tried googling the number you posted and get nothing. I have a KT-2938 that had a dim screen so I replaced c118. Hooked it backup and now have horizontal collapse. HOT didn't show short while in chasis so I went ahead and orderd a cap kit and replaced all caps. I now have a thin quater inch vertical line for a picture but its super bright. lol I'll be pulling and testing the HOT and two mosfets you listed tonight but even if my HOT is good I'd like to order a spared just in case.

I appriciate all your input on the forums. You've helped me repair many of my monitors without me even having to ask any questions due to your detailed responses to others questions.

Thanks

http://www.casinotech.com/kortek/spare_parts/transistors.html

Ok, Here it is.



Where your loosing horiz-deflection is thru the scan transformer

It is breaking down under load and kortek upgrade the coil and HOT thats

just part of the repair..

You can get by with your HOT you have for now untill you get SCT

that may be working in another chassis it is used in a few of thier chassis too..

The part is NLA what can we do..

Casinotech said they can't get anymore.

A very thin line could also be no 250vs on Q710 and in my notes

i found a bad trace at c130 so make sure you have dc on the mosfet..

and r732,q710 is good.

turn down you screen pot so you don't burn a line on the Crt.

just so you can see it during troubleshooting..

Good Luck!

 

[Ohmerone]

verified tube.

Hooked this chassis up to a 25" tv tube with a nanao dual res yoke( a litthe higher but close readings) and it produces a picture, no lightning storm.

WHen this chassis is hooked up to my laptops video out, all i get is a quick pic then it goes away, this repeats every 1-2 seconds. I dont know if that means the video section of this chassis needs recapped or if the monitor simply does not like the signal from my laptop.

Its progress i suppose.... just not quite what i had in mind lol.

So.. i guess i need to hope i can find a 29" tv tube somewhere cheap.

samsung tube# is a68qb892x

CM You need to use OEM parts to TS these chassis..

Your results may be different from my findings and confuse any readers

if not usings OEM yoke and Tubes, And some chassis use double focus

see manual for details..

Depending on the defective parts some of theses chassis may not get fixed.

 

[pcjohn]

Common problem, no solution ?

I've seen this in a lot of KT-2914Fs.

Monitor sort of works - the picture comes up but it is pulsing. The whole pic
fills the screen, then shrinks (blooming?). It's a constant cycle.

Replaced every cap on the chassis - still no difference. Looks almost like the
B+ is dropping out then kicking back in.

Any thoughts ?

JD

 

[AlucardXP]

Mine did this. It was a blown 19n20 MOSFET. It was the inside one that is attached to the heat sink but apparently there all known to go. I've still yet to finish fixing my chassis so it could be something else but I'd take a look at them.

 

[Ohmerone]

I've seen this in a lot of KT-2914Fs.

Monitor sort of works - the picture comes up but it is pulsing. The whole pic
fills the screen, then shrinks (blooming?). It's a constant cycle.

Replaced every cap on the chassis - still no difference. Looks almost like the
B+ is dropping out then kicking back in.

Any thoughts ?

JD

Need to replace the HOT and the transformer!!

the transformer T303 is NLA

buy a new HOT and borrow a working T303 from a another

working chassis, if you would like to see for yourself

look for the same numbers on the part.

When I had the parts, transformer ,HOT CAPS,MOSFETS when bad.

instock i would change them all on the chassis

coming in for repair and it took care of many of the intermitting symptoms.

The Old HOT will cause issues need to replace then test chassis again

after caps replace.. the Hv caps around the scan mosfets need to be check

along with each mosfet. They could look bad or check shorted

Have to eliminate each part, Good Luck!