[SOLVED] Black blob on WG 19K4914 arcade monitor

[vizzinni]

I just picked up a Mortal Kombat II cab from Craigslist, which turned out to be a conversion from a Gauntlet.  Got it cheap because it wouldn't power up, ended up swapping out the power supply which did the trick, although now there's a few issues like the black blob on the monitor, a WG 19K4914 manufactured in 1985.  Does this look like something a cap kit, or something else that's relatively easy, might fix?

[lilshawn]

that looks an awful lot like something inside the tube is casting that shadow.

you didn't happen to transport the machine laying on it's back did you?

does this blob change shape at all with brightness contrast? does it wobble or stay still? if you bang the side of the machine does it move at all?

[Ken Layton]

Yes it could very well be a capkit is needed.

[vizzinni]

you didn't happen to transport the machine laying on it's back did you?

does this blob change shape at all with brightness contrast? does it wobble or stay still? if you bang the side of the machine does it move at all?

I transported the machine upright, but laid it on its side briefly when sliding it off the back of the truck.  The blob stays still.  I've taken the chassis out of the frame so I can't try the brightness adjustment or the "bang test."  I just got the cap kit from Bob Roberts in the mail this morning, so I'll be trying that next.

[grantspain]

looks like damage to the tube imo,it should just notice in daylight without the monitor powered
the shape is far too random to be chassis fault

[vizzinni]

Thanks for the input guys...it turned out to be a bad cap.  I was looking through Randy Fromm's Big Blue Book and found a mention of a specific bad cap that could cause a "dark, irregular area," so I ordered the cap kit.  Fromm specified the C507 (47fu 160VDC) cap in the WG 4900 series, but I changed them all anyway, and the problem is solved. 

[grantspain]

well i am surprised by that,never seen anything like that in 30 years of working on monitors caused by a cap-unless it was a tear and the photo did not show well enough the actual issue

[lilshawn]

awesome it was something simple.

often things like this are the result of having a tub getting jarred with it's viewing face pointing up. (as it would if the machine was transported on it's back) this results in a piece of crud from inside the tube to get knocked off and down the back of the tube into the gun area. even a tiny piece of something can cause a shadow on the image, as the electron stream gets blocked by the debris.

 

[krick]

I just got the cap kit from Bob Roberts in the mail this morning, so I'll be trying that next.

It's good to hear that Bob is still doing his thing.  I was concerned when there wasn't an update to this...
http://homearcade.org/BBBB/status.html