K7000 Pulsing Curl

NCC-1701

New member
Joined
Nov 19, 2010
Messages
98
Reaction score
1
Location
New Jersey
I'm stumped on this one, K7901 installed in Ms Pacman, recently installed new flyback with the black knobs, VR, HOT, at some point in time the chassis was recapped with Jameco caps, got this thing dead with blown 1.5a slo blow still in holder, replaced the VR which had a dead short, plus the HOT, fired her up, all is well except the the right side of the Ms Pac Maze has a curl up and down the screen pulsating like a heartbeat, adjusted the vertical hold, slight improvement, still ticks in an upward direction, reminds me of a dog wagging it's tale, anyone experience this, normally would suspect a cap but the ticking movement has got me stumped.
 
your synk may be hooked up incorrectly.
this may be part of the curl problem.
try tweaking your horizontal position pot a little.

as for the pulsing it may be your filter cap is going bad.
was it replaced?
or one of the other caps is failing again.

Peace
Buffett
 
Originally the curl was much more pronounced, almost like a fish hook, still pulsatiing, trust me I play with all the pots until it straightened itself out, basically I have straight lines that tick up and down only on 1/2 inch end of the screen like squiggly worms, like I said really weird, I can recap the monitor and I do have spare identical parts chassis...by the way where is this filter cap intalled, and how do I test it.
 
How do I check the sync, 3 pin connector has 1 Orange harness wire from PCB going into pin 3 on the 3 pin chassis connector, then pin 3 is jumped over into pin 2 of the 3 pin connector, original monitor in this Ms Pac was a G07 with a bad tube.
 
its the biggest cap on the board. back rite hand corner.

you can't measure it correctly without an esr and uf meter.

it's just as easy to replace it when you cap it.

if you can post a video of your line and curl problem.

i would like to see it if possible.

Peace
Buffett
 
How do I check the sync, 3 pin connector has 1 Orange harness wire from PCB going into pin 3 on the 3 pin chassis connector, then pin 3 is jumped over into pin 2 of the 3 pin connector, original monitor in this Ms Pac was a G07 with a bad tube.


yea picture time.

synk is wrong.

pac is negative synk.

you should be using pin 9-10 or just 10 for the synk.

Peace
Buffett
 
Last edited:
try adjusting the 50/60Hz pot. It is the pot on the main board that faces upward, right behind the normal row of adjustment pots.

Okay will try tweaking this pot a bit, while I'm at it is there a B+ adjustment on this chassis, found one pot hot glued in position, not sure how to check the B + also need to know if it should read 120vdc
 
its the biggest cap on the board. back rite hand corner.

you can't measure it correctly without an esr and uf meter.

it's just as easy to replace it when you cap it.

if you can post a video of your line and curl problem.

i would like to see it if possible.

Peace
Buffett

I do own an ESR Meter, should this cap measure below 1/2 ohm, will try to post a video tomorrow so you guys can visualize the problem, it may be a bad cap but I thought that a bad cap would cause a steady curl not a heartbeat pulsing curl, we will crack this thing together
 
there is no B+ adjustment on a K7000.
its a fixed system.

25" = 130v
19" = 123v

black to the frame.
red lead on the big resister on the left outside resister tab closed to the tube.

Peace
Buffet
 
esr and ohm readings are two different things.

esr should be no more than 10-15% off for best results.

but the UF value could be way out even if the esr is good.

Peace
Buffett
 
okay, will revisit tomorrow, and I will post video on youtube with link, this problem seems pretty unique so I hope we can all learn from it.
 
Problem solved, sync was incorrect on the 3 pin connector, orange/red wire from pacman game board was wired correctly into the H position on the 3 pin connector which is correct for pacman which requires neg sync, only problem is that at some point in time a short jumper was added from the H neg position to the V position on the 3 pin, cut the jumper off the V position and now have a perfect straight picture, pulsing wiggle worms gone, used this Bob Roberts diagram to figure it out http://www.therealbobroberts.net/k7000lyot.html thanks for all the input.
 
Back
Top Bottom