What could be causing this problem? (MTC9000)

[MaximumFish]

Hi all,

I turned on my monitor over the weekend after a few weeks of being off and was presented with this image (see attached).

It kind of looks like what you'd get from moving the picture too far up the screen, where it would start to fold back down on itself, but I can't adjust the vertical position far enough to rectify it. Could it be IC1? (As suggested here.)

In addition to that, but not as serious, is that I get a constant wobble on the edges of the screen, like waves. I've previously tried replacing C57 to fix this, which the above link suggests, during which I also took the opportunity to do a complete cap replacement, but it didn't help.

So yeah, any sage advice would be highly appreciated before I invest more money in random parts that may or may not work!

Much thanks,

Max

[ericksonline]

Hi,
This is my first post here. I'm new to the arcade cab hobby, but I think I know what your problem is.

I just bought my first cab. The guy I bought it off of warned me that there were some problems with the monitor. There was a "wave" in it. When I went to look at it the wave wasn't too bad, but there was a vertical fold just like you are showing in your pic.
I bought it anyway (the price was too good). I played around with the adjustments on the remote board for 2 evenings, but I couldn't get things any better. In fact, things were much worse. Now, everything was so blurry that I couldn't read any text on the screen at all. After doing lots of reading, I came to the conclusion that it wasn't just a cap kit that the monitor needed. It probably also needed a new flyback transformer.
So, I was all ready to tear my cabinet apart and remove the monitor so I could get it repaired. Then I found out that there are 2 more adjustment pots on the flyback transformer. I barely even touched the "screen" adjustment pot and my problems have completely gone away (for now). Well... I take that back. When I first turn the game on, there is still a very minor wave for about 5 minutes. Once it is warmed-up, the monitor looks like new. I didn't "fix" my problem, but I did probably buy myself a couple of months.

I would say that your monitor needs a new flyback. Try to adjust the pots on your flyback first though. I needed a mirror to find the adjustment pots, then another mirror to see the screen as I made the adjustments. Just be careful where you are poking your screwdriver back there!

Edit: BTW, I have a Neotec monitor, so it isn't exactly the same as yours. I would imagine that they are all pretty similar though.

Ron

[grantspain]

could be a short within the flyback but that normally will give a total collapse,i would say the vertical frame ic is on its way out-be something like a tda1675

[MaximumFish]

Bumping to say thanks for the help. I've ordered a TDA1675 and a BU508A (to hopefully fix the wobble). I'll let you know how it goes.

@ericksonline - Thanks for the suggestion. The screen (voltage) control on the MTC9000 is nice and obvious so I'd already tried tweaking it. While reducing the voltage helps a little it far from fixes it.

[qrz]

u may find the IC simply needs resoldered .
heat over time will degrage solder integrity.

that said, the IC could still be failing, and/or smaller 'lytic caps
in the Vdrive circuit may be faulty....

always check cheap/easy 1st 

[lilshawn]

u may find the IC simply needs resoldered .
heat over time will degrage solder integrity.

you will find too, that there is often a severe lack of thermal compound on these chips, causing them to run hot and begin to fail. depending on the design, some chassis didn't even use a heatsink and just left them exposed to the air for cooling. (i add heatsinks the parts like these)

[qrz]

you will find too, that there is often a severe lack of thermal compound on these chips, causing them to run hot and begin to fail. depending on the design, some chassis didn't even use a heatsink and just left them exposed to the air for cooling. (i add heatsinks the parts like these)

in almost 30 years of servicing, i've never encounted a vert output ic that wasn't attached to a heatsink.
( granted, albeit poorly at times )
the currents involved generate heat that must be dissipated for longevity of the device....

[lilshawn]

sorry, the statement was meant to be non-specific. (i was tired and just drove like 700 miles to get back home this weekend.)

some switching trasistors and other whatnots sometimes don't have heatsinks. some designers figured they could save a few pennies use a 3 amp trasistor to switch a 1 amp load and get away with not using a heatsink.  :angry