Megatouch Type 51 Telcovision KT-1403V color problems [RESOLVED]

[Arm123]

I recently had a megatouch maxx emerald with a whining monitor.

The picture was dark, blurry and the contrast was way off.  The brightness and contrast had to be cranked high to see things properly and the colors would bleed from the high contrast.  Also the color was really bad with a red / pink tint on the right half of the screen, which is most noticeable on white backgrounds.  Also, text was blurry and unreadable.  Calibration was impossible with the breakout or monitor controls.

So i changed a bunch of caps as suggested on the merit website.
http://www.meritind.com/Service%20Center/Technical.htm#MONITOR

I must say that the picture is VASTLY improved.  The monitor runs silent and the text is sharp and readable now.  Contrast and brightness are restored to a decent level.

However, i can still notice that the right side of the screen has a red / pink tint.  I removed the monitor chassis to see if it was some kind of magnetic disturbance inside the game housing.  The red / pink remains on white / bright pictures.  Its not very noticeable on dark pictures (which are most megatouch games) but I am wondering what it could be ?

I noticed that the neck board was a bit crooked.  So pulled it off and put if back on to make sure it was snug.  Still, the red / pink tint persists.  I will update this thread with some pics as soon as i can.

What could cause this ?  Should I try a manual degaussing ?  Should i change the rest of the caps on the board ?

An suggestions are very welcome.

Thanks

[Ken Layton]

This monitor has a TON of bad caps. It is suggested to replace them all. I wrote a repair guide to this monitor. I have successfully repaired well over 50 of these monitors over the past 10 years.

I just got another 16 of these monitor chassis shipped to me for repair from The Megatouch Store in Murfreesboro, Tenn.

[Arm123]

This monitor has a TON of bad caps. It is suggested to replace them all. I wrote a repair guide to this monitor. I have successfully repaired well over 50 of these monitors over the past 10 years.

I just got another 16 of these monitor chassis shipped to me for repair from The Megatouch Store in Murfreesboro, Tenn.

yup...  a simple google leads me to all kinds of complaints about this baby !  I will go ahead and replace the rest of the caps and update this thread when done.

Thanks, for the reply and if you have any other advise or thoughts about this monitor, feel free to add them here 

[Ken Layton]

It's actually a good monitor once ALL the electrolytic capacitors are replaced. Caps C425, C501, and C315 are particularly troublesome. Be advised that the polarity markings on the foil side of the board for cap C501 are wrong. It is marked correctly on the parts side of the board though.

There's also 'early and 'late' versions of the chassis too. Some component values are different between the early and late chassis. You should email me if you want a copy of my repair guide to this model.

[Arm123]

It's actually a good monitor once ALL the electrolytic capacitors are replaced. Caps C425, C501, and C315 are particularly troublesome. Be advised that the polarity markings on the foil side of the board for cap C501 are wrong. It is marked correctly on the parts side of the board though.

I have not replaced those caps yet, but i usually check both the board and the old cap i remove when changing them.  Good thing you told me or i think i may end up doing somthing stupid 

Thanks again

[Arm123]

Ok...  i finally got around to changing all / most of the caps on this monitor.

I turned it on and all i see is white !..  What could this be ?  I left it on for a minute or two and heard some cracking / popping from the tube.  I know iv heard someone bring this up before.  What could this be ?

The only good thing is… the whites are WHITE !  The pink tint is gone.

How can you tell when a CRT tube is no good / dead ?

Any ideas ?

Thanks everyone.

[Ken Layton]

Did you read the guide I emailed you?

Always check the placement of the focus and screen wires so they don't scrape against the flyback cage and abrade their insulation. Make sure the yoke wires aren't scraping against the sharp edes of the vertical output IC's metal heat sink fins.

Double check the polarity of all the caps you put in. My guide mentions some that have either no polarity markings on the chassis or the markings are incorrect on the foil side.

[Arm123]

Hey there Ken, thanks for the reply.

Your guide was EXTREAMLY helpful.

I was very careful to mind all polarity settings and contacts.  I followed the polarity settings on the parts side of the board and checked the old cap settings.  The last person to service this messed it up.  The trace lines are very close to coming off on a couple of the caps that needed changing.  I managed to do the best I could and then did continuity tests on them to make sure things were kosher.

I replaced ALL caps at the same time because I am uncomfortable with discharging monitors (I haven’t fixed very many) and I didn’t want to replace a few… check and discharge…  replace a few check and discharge… etc.  I am not as seasoned as you or other veterans on this board at servicing monitors and the high voltage makes me nervous ;-p

I did use a 25k ohm 1w resistor between my pair of clips to my screwdriver and chassis to lessen any load when discharging.  Any other advice safety tips in this area appreciated.

Nothing happened each time I did it so I am comfortable doing it now.  I should I have only done a few caps at a time and checked but now I know better  ;-p

The only thing I can think of that may be a problem are C612, C616, C618...  I couldn’t find any caps that were 3.3uf by 100v.  So I had to use 3.3uf by 450v to replace them.  I know, as a rule, you shouldn’t use more that 2x the operating voltage of a cap.  But besides spacing issues, would this mess things up ?

Also, I must have a really early version of this board because C313 has a value of 22uf 50v and I am a bit confused as to what I should do regarding your guide instructions, so I didn’t change that one.  Should I change it to the new suggested cap value ?  or one of the same value ?

Also, the screen would start out with a faint image...  then start turning white and whiter until nothing but white was seen.  Does this indicated a solder contact problem with too much, or unexpected voltage leaking to a place where it shouldn’t be (ie: bad solder point) ?

I haven’t turned the monitor back on since I heard the cracking / popping and shut her down.  To be honest it scared the living ---steaming pile of meadow muffin--- out of me ! ;-p  Would that kill my CRT ?

Thanks to ALL who are taking the time to advise me.  I am trying to be as descriptive as possible as I know info on this monitor is very limited.

ANY tips, or things that would be helpful to know, are MOST welcome.

Thanks.

[Ken Layton]

One thing I didn't mention in my guide, but I've run into more and more is the metal frame the main board is bolted to can get bashed/bent/twisted inwards enough to touch several foil traces shorting them to ground. Pay attention to the frame near transistor Q302 to resistor R319's foil traces getting shorted to the frame.

If your C313 has a 22uf capacitor there then replace with the same value. Also there are several components around the outer perimeter of the main circuit board that can get mashed down and their leads either touch an adjacent component (bad) or short to ground. Pay particular attention to the 2 watt resistor near the metal clamp securing the video input cable.

[grantspain]

sounds like the screen volts is shooting up to maximum,something like a bad solder joint or trace or maybe something shorting out-just go over everything you have done and recheck it

[Arm123]

If your C313 has a 22uf capacitor there then replace with the same value. Also there are several components around the outer perimeter of the main circuit board that can get mashed down and their leads either touch an adjacent component (bad) or short to ground. Pay particular attention to the 2 watt resistor near the metal clamp securing the video input cable.

Thanks very much for your replies Ken and Grant.

I will go threw all my caps and verify they are soldered well.  And check the above things you mentioned Ken.

However, i did smell something strange when the monitor made that popping sound.  Should i be concerned about that ?

Thanks guys.

[grantspain]

pop noise followed by strange smell=incorrect polarity of a cap,look for a burst outta the top of one of the caps you replaced

[Arm123]

I see a cap thats completely missing !  Perhaps it blew up and poped off...  I replaced it and i still got nothing.

This weekend im gonna go threw everything i did and double check.

Also, whats a 'sure fire' way of telling weather or not your tube is dead ?  If i got all the chassis compnents working and the tube still does not power up.  Where can i test and check if the tube is powering up / opperational ?

Thanks.

[Ken Layton]

Buy a used high voltage DC probe on ebay. Then you can measure the high voltage going to the tube.

[Arm123]

thanks Ken.  Im on it  ;-)

Just incase i cant get this 8itch to work... Is there anyone willing to sell me a used 13" monitor and ship to Canada ?

Thanks

[Ken Layton]

Check with david@themegatouchstore.com (phone 615-364-5655) as he sells new and used parts for Megatouch games.

[Arm123]

ok...

I took a couple hours and went over all the caps i changed.  All seems well.

Checked all the solder joints and places that were suggested may be shorting.  Everything seems fine with the chassis and neck board.

When i power up the  machine i can hear a "buzz" and usually after that i can hear the CRT power up.  But since i heard the popping / cracking sound with smoke last week, i cant hear the CRT power up anymore.

I can see the coil on the yolk still working / glowing.

My guess is that the Flyback isn't working and thats ware the smoke came from, cuz i cant see new burn marks anywhere else, and have tested most everything else.

I dont have a High voltage probe.  Is there any other way i can test that the tube is receiving power ?

Thanks.

[Ken Layton]

Check resistor FR101 to see if it's gone open or off value. As mentioned in my repair guide it should be 2.2 ohms 2 watts. It's located by the largest yellow transformer on the chassis. If the resistor is open then the vertical output IC (TDA1675a) is bad and both the resistor and this IC must be replaced.

[Arm123]

Hey there Ken.

I did indeed check FR101 and IC (TDA1675a).  The values are fine and the IC checks out.

I just bought this:
http://www.keithley.com/products/instaccessories/?mn=1600A
And some Salisbury Lineman High Voltage Insulated Gloves   ;-p

Im waiting for them to arrive so i can check values of the flyback at the anoid cap.

Any advise ?

[Ken Layton]

Check the neckboard for cracks. Also on the neckboard are 3 wires from the main board: white-black-blue. Make sure where they're soldered to the neckboard they aren't accidently touching each other. Also the three white resistors on the neckboard and the three large heat-sinked transistors develop bad solder connections.

[Arm123]

Hey there Ken.

I have gone over the neck board and chassis extensively.  I am gonna take some pictures to get your opinion.

When the monitor is powered on, i hear the degaussing coil buzz, then nothing.

I have read that when a Flyback starts going bad, sometimes you receive a blurred display / picture.  This was indeed the case, until i CRANKED up the screen control to MAX on the Flyback.

Isnt it reasonable to conclude that the Fly back is indeed the fault and went bad ?  I know it is hazardous to do so, but what can i do to test it ?  I am taking all safety precautions. (gloves, glasses, rubber matt, insulated tools, high voltage probe, one hand in pocket...  etc).

Can i take the protective plastic caps off of the yoke and take readings there ?  Just to see if indeed the monitor is powering up.

Ill get those pics posted.

Thanks, Andrew


[edit]spelling[/edit]

[Arm123]

I just picked up 7 touch screen machines.  5 of which are running perfectly.  2 need service.

1 of the 2 that need service has an Orion picture tube.  Im going to compare part numbers and see if i can make a swap, if my other Orion turns out to be bad.

Here is a nice little article i read if all fails.

http://www.ews.uiuc.edu/~nshin/PROJECTS/ARCADE/monitor_tubes.txt

[Arm123]

Thought i would update this thread for the benifit of others.

I got it working by replacing FR102 and IC601.

Special thanks to Ken for all his help.

Also, the RED / PINK tinge is gone.  These monitors actually look pretty good once running well.  I, for one, was suprised.