Neotec NT-27V - Red Horizontal Lines

[jhoyt]

I recently purchased a Neotec NT-27V (this is the number taken off of the neck board)  off of ebay that was removed from a Golden Tee game.  For the most part the monitor works great, but it is displaying several equally spaced red horizontal lines (around 15 from top to bottom).  Additionally, the display is a bit red washed.  I have adjusted the colors to reduce the red level, but the monitor is still a bit red washed.  Additionally if I turn the red level completely down, the lines remain changing colors.  Any suggestions on what I can do to fix the problem?

Additionally, I am considering purchasing a cap kit and replacement flyback for the monitor, but have been unable to find exact matches for this monitor.  I can easily find cap kits for the NT-2702 (Neotec's newer 27" VGA monitor), does anyone know if these are in fact the same monitor?  I have an email out to Neotec, but have not head back from them yet.

[grantspain]

sounds like a leaky transistor on the neck card,you could swap the drive transistor from red to blue to see if the problem moves to the blue
100% it ain't flyback and pretty sure it ain't a cap

[SirPeale]

I agree with Grant.  Either a leaky transistor or a red short in the tube.

[grantspain]

i am pretty sure the letter does denote the frequency type of neotecs,i have  neotec nt-27e in my artic thunders which are 25k(ega) so its quite possible your monitor is vga(it would have a vga plug though-that would make it very obvious)

[jhoyt]

i am pretty sure the letter does denote the frequency type of neotecs,i have  neotec nt-27e in my artic thunders which are 25k(ega) so its quite possible your monitor is vga(it would have a vga plug though-that would make it very obvious)

I definitely know that it is a VGA monitor (like you said, the cable gives it away),  I was more wondering whether or not Neotec's NT-2702 (http://www.neotecgraphic.com/detail.asp?TABLENAME=VGA_Monitor&ID=4) uses the same boards as my NT-27V.  I can easily find repair parts and schematics for the NT-2702, but have had no luck in fining them for the NT-27V.

[grantspain]

i would say yes

[jhoyt]

I just heard back from Neotec and the answer is no the NT-27V and NT-2702 are similar, but definitely not the same.  I am looking over the schematics now and there are major difference between the two.  I have asked Neotec's permission to post the schematis on the forum.  If they grant me permission I will put them up ASAP.

As for my issue with the red washed monitor and horizontal lines, I have yet to swap the drive transistor (I will give it a go next weekend).  I will post the results.

Thanks Grant and Peale for the help!

[jhoyt]

Well I swapped the red and blue drive transistors and had no luck.  I'm still seeing a red washed screen with horizontal lines.  Any other suggestions on what may be the cause of the problem?

[SirPeale]

Red short in the tube.  You'll need to get your tube rejuvenated.

[jhoyt]

I was beginning to suspect that, especially since the monitor has also started to become overly bright.   

Anyone know of a tv repair shop near Baltimore, MD that has a tube rejuvenator?

Thanks for the help!

[Kevin Mullins]

Disconnect the red input signal completely and see if it still has a red tint to it.
If so, then you know for sure it's the tube itself.

Turn the SCREEN voltage down on the flyback to see if the lines will go away.

[jhoyt]

Thanks Kevin, adjusting the screen voltage made the lines go away.  Still trying to figure out how to remove the red input without cutting a cable...

[Kevin Mullins]

Thanks Kevin, adjusting the screen voltage made the lines go away. 

Cool .... is it still bright enough and look good other than the red problem?

Still trying to figure out how to remove the red input without cutting a cable...

Depends on what kind of connector you have. Should be a little tab of some sort to push and unlock it from the rest of the connector.
Some require a tool to make it simpler, some just need a tab pushed down from the backside.

[ESDAVE]

hi kevin it sounds like you have a short on red gun called heater cathode short , to have it rejuvenated IE cathodes cleaned  with hi voltage wont help it , if some one has a machine to clear short that possible will . an easy/ safe way to check if you have h/k short is to use an analogue meter ,you can use a digital one if you want but i find analogue better for this test,.  on ohms range set to approx x100 a connect between red cathode and heater you should not have a reading .use green or blue as a reference to see what it should read, ie no reading . DO THIS UNPLUGED. i can give you more information to temporally or poss permanently clear it. kind regards dave eng England.

[Kevin Mullins]

hi kevin it sounds like you have

Mmmm .... it's not me that has the problem. JHOYT does.

But great advice though. 

[ESDAVE]

oops sorry kevin, they will probably take me back to the home tomorrow and i should be ok after my medication. i hope JHOYT will see it . dave

[jhoyt]

Cool .... is it still bright enough and look good other than the red problem?

It looks much better and it is thankfully just bright enough, unfortunately I have brightness turned all the way up.  I'm recapping the monitor today, so hopefully that will help a bit.  Even if it doesn't the monitor is in bad need of recapping based on the charred look of some of the caps.

Depends on what kind of connector you have. Should be a little tab of some sort to push and unlock it from the rest of the connector.

Silly me, the vga connector is held on by screws.  This should make things much easier.  I will try to isolate the red once I finish my recapping extravaganza.

[jhoyt]

hi kevin it sounds like you have a short on red gun called heater cathode short , to have it rejuvenated IE cathodes cleaned  with hi voltage wont help it , if some one has a machine to clear short that possible will . an easy/ safe way to check if you have h/k short is to use an analogue meter ,you can use a digital one if you want but i find analogue better for this test,.  on ohms range set to approx x100 a connect between red cathode and heater you should not have a reading .use green or blue as a reference to see what it should read, ie no reading . DO THIS UNPLUGED. i can give you more information to temporally or poss permanently clear it. kind regards dave eng England.

Dave, thanks for the tip, I will check that out today after I recap the monitor.

[jhoyt]

an easy/ safe way to check if you have h/k short is to use an analogue meter ,you can use a digital one if you want but i find analogue better for this test,.  on ohms range set to approx x100 a connect between red cathode and heater you should not have a reading .use green or blue as a reference to see what it should read, ie no reading .

Dave, I'm just making sure I understand where I should be measuring, but it is between the H and K pins on the back of the tube correct (i.e. remove the neckboard and measure between the pins)?  If so, then I get no reading (open circuit) from KR to H1 or H2 as well as KG to H1/H2 and KB to H1/H2.  Sorry, I'm new to monitor repair thankfully I have some electronics experience...

[Kevin Mullins]

If so, then I get no reading (open circuit) from KR to H1 or H2

Then you don't have a heater to cathode short.

Additionally if I turn the red level completely down, the lines remain changing colors.

When you turned the red down, did the washed out red go away as well?

Have you tried turning down the red DRIVE potentiometer?
There should be two adjustments for red, a DRIVE and a GAIN. (maybe labeled differently on yours)

Try turning those both all the way down.
You should be able to make red disappear completely by turning both of those all the way down.

Do they BOTH make a change in the screen color?

One at a time turn them back up.
One of them (drive if I recall correctly) should remain fairly low. And use the other to adjust to your liking colorwise. One will have a much harsher adjustment scale. (I always get drive and gain confused for some reason myself)

[jhoyt]

When you turned the red down, did the washed out red go away as well?

Have you tried turning down the red DRIVE potentiometer?
There should be two adjustments for red, a DRIVE and a GAIN. (maybe labeled differently on yours)

Try turning those both all the way down.
You should be able to make red disappear completely by turning both of those all the way down.

Do they BOTH make a change in the screen color?

Kevin, thanks again for the help.  I was just adjusting the drive red and not the gain.  Regardless, the gain's potentiometer was shorted.  Thankfully after replacing the potentiometer, everything is now fixed showing very good colors.  The gain and brightness are both still all the way up, but I can live with that now that the colors look good.

[Kevin Mullins]

The gain and brightness are both still all the way up

As far as th RED gain and drive, you'll have to just play with both of those a bit to get what you want out of the red.
Either way.... BOTH should make a noticable difference, one just greater than the other.

There should be an actual "brightness" pot. Is that the one you say is all the way up?

If you need it brighter..... check for a "contrast" pot and you may be able to tweak up the SCREEN voltage a bit on the flyback. (just not to the point where you have lines again)

Sounds like you have a handle on it.
Just a matter of playing with it a bit to your satisfaction.

[jhoyt]

yes, both the brightness and contrast pots are up all of the way.  By adjusting the screen voltage, I was able to reduce them a bit.