Kortek KT-2914F Neck board issue (Occasional blue tint)

[Yoeddy1]

Hi All,

I've had an intermittent issue with my Kortek KT-2914F 27" monitor where the screen will flicker a bit with a blueish tint off and on and then it goes back to normal.  No other problems, just this blue overlay then it resolves itself.  Well, I took the monitor out of the cab.  I banged around on the monitor a bit and couldn't get it to flicker.  Finally I was tapping the neck board, and this is where I can reproduce the problem. Sometimes I can wiggle the crap out of it and it won't exhibit the problem, and then other times I can lightly tap it, and the blue tint will cover the image, and then it goes back to normal.  Sometimes, I don't need to touch it at all and the blue tint will flicker on and off over the image.

Any thoughts what it could be or where to start?

Thanks,
Jason

[MonMotha]

Probably a cold solder joint on either one of the drive transistors or one of the big power resistors.  The connectors (for the cables going to the neckboard) also sometimes have issues with bad solder.

[Yoeddy1]

So I have a story to tell...

I'm a real novice with this stuff, so I decide to call a local company here in Boise, Idaho.  I take the monitor in and he has the monitor for an entire afternoon.  I get a call from him and he claims that he can't reproduce the problem.  Claims that it's probably an issue with my PC (MAME).  He says that I can come down and pick it up.  No problem.  I go down there and he says that it's been on for two days and he never saw the problem.  I'm a bit concerned with the troubleshooting at this point.  At any rate, the flicker starts and I quickly show him while he had it on.  He acted surprised.  He started flicking the neckboard and the thing REALLY started exhibiting the problem.  I tell him I can leave it there for a few days now that we have the source narrowed down. 

I hear nothing for a week.  I decide to call.  The tech is nowhere to be found, but I talk to the office manager who calls the tech to get the lowdown.  I get a call back and he apparently changed a video color driver and all caps looked good.  I was told that I could pick up the monitor.  2 bucks for the part and 190 bucks for the labor.  Ouch, but ok I guess. 

So I get the monitor home and I power it up.  STILL DOING THE SAME THING!!!  I'm livid.  I call the shop and leave a message.  About 3 hours later, I get a call back from the owner.  He's immediately on the defense and I explained to him that the problem was still there.  He immediately proceeds to tell me that they never said it would be fixed, and that he has to pay his employees.  He made me feel like complete crap, and I told him that I only wanted to explain my situation and what we could do for next steps.  He said that there was nothing that he could do and that my monitor was shot.  In addition to the blue flicker as described in the first message, I'm also getting a complete drop out...almost like the blue is completely gone.  Red, yellow, green seems to be ok, but no blue at all.  If I power off the monitor and power it back up, the screen looks perfect...for a while.  Blue flicker is still intermittent.  I finally went to blows with this jerk and he agreed to split the cost 50/50.  What was surprising was right off the bat, he said he never wants to do business with me again and won't allow any of my equipment to be brought to his establishment.  What did I do wrong?  I asked for his help was all. 

So I'm desperate at this point guys.  Is there anyone in the Boise, Idaho area that can help me?  I'll certainly pay someone to help fix this.   I posted some pictures.  The Punchout with the blue in it is correct.  The Punchout lacking blue is when it is a problem.  The third photo illustrates what was replaced and the note.

Thanks for any help! 

Jason

[Yoeddy1]

Taking the monitor into a repair shop next week.  Before I do, I thought I'd share a couple of videos.  Any ideas on what could be causing this?

You'll see the monitor get a blue'ish tint that will just randomly come and go.  Could be when the monitor is first turned on, could be hours after it's turned on, may not happen at all.  I did see the entire image go completely blue before and some of the graphics were smeared almost as if somebody put their finger on the screen and smeared the graphics to the right.  Seconds later, it cured itself.  Anyway, any help would be appreciated.





Thanks,
Jason

[ed12]

use a crt chker to chk the blue gun for heater to cathrode chks
this is a common problem..red/green/blue go bright then go right back...
u will need to rejuj it and or :blast it:,the last resort :blast it is a total death call:
as rejuv reduces the life,but the tube is on it's way...so simple question to ask the shop
owner do u. u sir own a crt rejuanter ?,simple q,simple answer yes or no

ed

[Yoeddy1]

Hey guys,

I'm back. I've now had my monitor into 2 shops, and neither could figure out the problem. They both seem to think it's not a problem with the tube. Solder joints have been reflowed on the neck board, but that didn't help. The blue tint overlay happens and can smear the image, and then it just fixes itself and goes back to a stellar picture.

I noticed that there is an EPROM on the chassis. Is there a possibility that this could have gone bad? What does this EPROM control? Would it have anything to do with my problem?

Thanks,
Jason

[ed12]

yup
replace with fresh=new...

i did speak about this problem in a thread


ed

[Yoeddy1]

yup
replace with fresh=new...

i did speak about this problem in a thread


ed

Ed, how would I find a new one?  Could you point me to the thread?

Thanks,
Jason

[Yoeddy1]

Also, do I just take the old one out and put in a blank one? What are the specs of the EPROM?  Or is this a chip that comes from the factory with data written to it?

Jason

[ed12]

8 pin eeprom
either 93lc-xx
and or 24lc-xx
either are :pc-micro-controller's:

de-solder..reomve old..watch board :mark: for pin 1
place in new 1 >fresh< >fresh< as in brand-new
again pin 1 to 1
onuce u are sure.? plug unit back in..wait about 30 sec's to 45 sec's
adjust away to correct fault..once done follw EXACTLEY as i told a op on this matter..the thread is there

ed

[Yoeddy1]

8 pin eeprom
either 93lc-xx
and or 24lc-xx
either are :pc-micro-controller's:

de-solder..reomve old..watch board :mark: for pin 1
place in new 1 >fresh< >fresh< as in brand-new
again pin 1 to 1
onuce u are sure.? plug unit back in..wait about 30 sec's to 45 sec's
adjust away to correct fault..once done follw EXACTLEY as i told a op on this matter..the thread is there

ed

Thanks Ed.  Do you have one of these EPROM's available that I could purchase from you?  So remove the current EPROM, install the new EPROM, turn the monitor on, and what am I going to see?  I didn't really follow the last part of your message?

Thanks,
Jason

[Yoeddy1]

Ed, I was also referring to the large EPROM labeled KT-2914F Rev3.  Is this the same one that you are talking about?

Thanks,
Jason

[MonMotha]

I don't know if it will re-initialize them like the Wells do, but it probably would.  The EEPROM is U501, "C41DC", which is better known as a 24C04 in the Americas.  I've got one Kortek where it may be bad...doesn't save some settings but also hasn't gone bonkers, either, like the Wells do when the EEPROM goes bad.

The large part is actually not an EPROM; it's an entire microcontroller with built in flash memory.  You cannot just replace it unless you find one with the same (or a compatible enough) program on it, such as from a donor unit.  I've never had this part go bad.  it's pretty well isolated from all the nasty stuff on the monitor; it just generates signal timing and handles some OSD functions.

[Yoeddy1]

I don't know if it will re-initialize them like the Wells do, but it probably would.  The EEPROM is U501, "C41DC", which is better known as a 24C04 in the Americas.  I've got one Kortek where it may be bad...doesn't save some settings but also hasn't gone bonkers, either, like the Wells do when the EEPROM goes bad.

The large part is actually not an EPROM; it's an entire microcontroller with built in flash memory.  You cannot just replace it unless you find one with the same (or a compatible enough) program on it, such as from a donor unit.  I've never had this part go bad.  it's pretty well isolated from all the nasty stuff on the monitor; it just generates signal timing and handles some OSD functions.

Thanks for the reply.  On the photo of the board, which EEPROM is U501, "C41DC", 24C04?  Today, I had blue completely missing (like in the attached photos), and if I reboot the monitor all is well.  I have been getting a solid blue image off and on where it smears the complete image as well, but then, it just fixes itself.  Is this EEPROM soldered to the chassis or is it socketed?

Know where I can get one?

Thanks,
Jason

[ed12]

24lc-xx is a common chip..u can buy it just about any-where...
just do as and the other sujest..replace it with fresh,the :main: chip will re-write it..
up-side is u gain control again..also when them chip's go side-way's which they will
it will drive your horz to the point where the hot will and i mean will fail...
nasty little thing's
atmel can send u some..if u are nice? they will send u sample's 

ed

[Yoeddy1]

24lc-xx is a common chip..u can buy it just about any-where...
just do as and the other sujest..replace it with fresh,the :main: chip will re-write it..
up-side is u gain control again..also when them chip's go side-way's which they will
it will drive your horz to the point where the hot will and i mean will fail...
nasty little thing's
atmel can send u some..if u are nice? they will send u sample's 

ed

Thanks Ed!  Let me know what you need from me to get one of those in the mail.  If it's just soldering a new chip onto the board, I might be able to handle that one. 

Jason

[ed12]

the chip is indeed soldered in..
up-load a picture of your chassic i will pin-point the chip for u

ed

[MonMotha]

Is this EEPROM soldered to the chassis or is it socketed?

8-pin DIP northwest of the big micro with the label, as your picture is oriented.  it is unfortunately soldered down, not in a socket, but these are single sided boards without plated holes, so a little solderwick makes easy work of getting the old part out, especially with so few leads.  You may as well go ahead and socket the new one to make possible future replacement easier.

I checked my parts bin, and I don't have any 04s.  I have an 02 (pull), a bunch of 01s, and some 64s.  They're cheap, though.  You can probably get someone to sample them to you (Atmel, ON/Catalyst, Microchip, etc.), but it may take a little while if you don't know any of your local reps.  Digi-key, Mouser, etc. will definitely have something in stock, and you'll probably pay more in shipping than the part cost.

[ed12]

MonMotha
is correct
it is the 1 just south of the micro which is the 1 with the white label on it..
i do not have any 24lc08 here but i will chk the warehouse tommrow i have a few  of them chassic there,which i can pinch a chip out of until i get my replacement's.

ed

[Yoeddy1]

Thank you so much guys.  Or if you could send me some links to the parts themselves from the vendors, I can purchase a socket and the chip myself.  I just need a direct link to the parts so that I know what to get.

Thanks,
Jason

[MonMotha]

Should be a suitable IC:  Digi-key P/N AT24C04C-PUM-ND or 24LC04B-I/P-ND

Suitable socket:  Digi-key P/N 609-4717-ND

(For some reason the links seem to break...grr)


Less than a dollar in parts   Digi-key will do USPS first class mail parcel for about $2 IIRC.

[ed12]

fyi u can use a 24lc08 in place of the 04..the last digit's=the ram in the chip..
DO NOT US A SOCKET..
the reason is simple and the fix is just a simple
if u look at where the chassic sit's and that chip..u will find the chip sit's right under the picture tube...DO I HEAR STATIC ?..up every time..
that s what makes the chip's sour..STATIC from the  TUBE..
cure is easy..a small piece of foil tape on top off the chip >just the chip and not the legs's<..
will cure your problem..once u replace the chip with a fresh 1..
and yes they are about a buck or so..

ed

[ed12]

sorry bud u are sol..another tech used the last 1's..
if u can wait i have 100 on order

ed

[Yoeddy1]

Ok, I ordered a few 24LC04B-I/P-ND's from Digi-Key.  I'll cover it with foil tape as you stated...not on the legs...just the chip.  Would it be worthwhile to cover all of the EPROMs or just the 24LC04B-I/P-ND? 

By the looks and description, I'm assuming the chip is the one that I've highlighted in yellow in the photo right?

Thanks,
Jason

[ed12]

yup thats the 1

ed

[Yoeddy1]

Just foil tape that one Ed?  Or do you recommend foil taping all of them?

Jason

[ed12]

we olny do that 1..
it was a factory mod for rca/zenith/samjunk
believe it or not..i have the memo still to this day

ed

[Yoeddy1]

Well shoot.  I got the chip, bought some foil tape, pulled the chassis, de-soldered the old chip, soldered in the new chip, put a small piece of foil tape over the new chip, got her all back together, and the same issue occurs as what's in the videos.  Here's the crazy thing.  I managed to get my hands on another 2914F tube.  I connected the chassis to the other tube.  Same issue.  So at this point, it seems to be with the chassis.  Another data point...

I went into the settings and under the temperature settings where you can select User RGB settings, warm (6x000), cool (9300k), I can select any of them, but USER RGB settings will change, and 9300k will produce a different display, but when I select warm, it doesn't change.  Which chip on the chassis controls settings.  It's almost as if something is wrong there as warm settings won't take.  They definitely used to.

Thoughts?  And again, thank you all for the help!

[MonMotha]

Does giving the chassis a good whack or the neckboard a SLIGHT whack cause any change?  This could just be a loose solder joint in a color path.

Otherwise check basically everything on the neckboard in the blue path, including maybe the color amp and OSD chip (IC802 and IC801, respectively).  The main chassis pretty much only handles deflection, so a problem with a single color is probably going to be on the neckboard.  Only thing I can maybe think of is the micro that does the OSD control (but not the actual overlay) may be going bonkers and spamming the OSD overlay chip on the neckboard with bogus commands or similarly spamming the color amp chip with bogus gains, but this seems unlikely given that you don't seem to have any other abnormal operation.

[Yoeddy1]

So I'm assuming everything with a "B" after it, would be considered the "blue" path on the neck board?  I found the two IC's that you were talking about on the neck board. Tapping it doesn't seem to make a difference.  Would Q803 (looks like a transistor with a heat sink screwed to it) need to be replaced?  What part number would that be for that transistor?  Do RGB all used the same transistor, or is blue a special part number?

Do you think the EPROM on the chassis with label on it that is socketed could be a problem? Would it be worth removing that and reseating it?

Thanks
Jason

[MonMotha]

The transistors normally fail open/shorted, but I could see a potential thermally cyclic effect that would appear essentially random to outside observation.

Doubtful that "EPROM" (which is actually a microcontroller with embedded flash memory) on the deflection board would cause this, but you can reseat it if you like.  Shouldn't hurt anything to do so, but be aware that, since it's a half-pitch part, the leads are a little flimsy compared to standard DIP packages.

[Yoeddy1]

So....

I might be able to get another kt-2914F...not working.  If I was able to get this, is it possible to just take the neck board off, and switch it with the other one?  Or does the flyback need to go with it?  Do I need to de-solder anything, or is it just a matter of swapping the neck boards?

Thanks,
Jason

[MonMotha]

The focus line is soldered to the neck socket as typical.  Everything else can be unplugged on one end or the other.