4900 missing red but only Vertical

JoeB1355

Well-known member
Joined
Dec 11, 2010
Messages
1,631
Reaction score
99
Location
Seymour, Tennessee
So I'm working on an unknown 4900. I swapped the crt and capped it. I also swapped the neck board with another since the original was cracked

So here is the weird part.

I use my pattern generator with cross line grid and test each color one at a time

blue good

green good

red only has horizontal lines?? Its missing the vertical crossing lines

So is this weird or are there separate drive transistors for horz and vert for each color?

i only have this 1 semi working 4900 and a couple of parts chassis missing pieces and cracked to hell.

Could it even be the tube? I had to crank screen all the way up and black level to get a pic as well

Here are some pics

Blue (green looks correct like blue)
DSCF1363.jpg


Blue & Red

DSCF1365.jpg


Red

DSCF1367.jpg
 
Try it with a game board. The signal generator may be having an issue doing the red grid...
 
Yeah already did that on my centipede and the letters look weird missing little bits. So I broke out the generator to check it
 
it could be but i dont think so.

check transistors Q203-208. and all the traces to and from the 4 pin header that goes to the neck board.

Peace
Buffett
 
on closer inspection of my neckboard the one I swapped has different transistors and 2 different capacitors

as well I forgot to plug in the extra red wire on the neck board! Doh! I bet that's why I had to crank the screen & black level. Found another one that matches in the junk pile gonna try it.

I'll post back when I done
 
Almost good now! The different neckboard and red wire did the trick. I was able to adjust the black level and screen and the missing red lines showed back up when I was adjusting the black level.

I am getting a little "static" and white flashes ocassionally -- Did I fry the fly?

if I get white flashes is that a sign of a bad fly?
 
Back
Top Bottom