U5000 Just 'Ticking'

[MK3FAN]

I recently acquired a WG U5000. It worked, but the picture was horrible. It had some resistors in series installed in the B+ pot location instead of a pot. I removed the resistors and installed the pot. I also installed a cap kit and a new flyback. After I hooked it up and and turned it on, all I got was a thin horizontal line across the screen and after a couple seconds, it went away and now all I hear is a faint 'ticking' and nothing else happens. Any ideas? Thanks in advance!

[qrz]

i hope u matched the pot to the fixed resistance before pwr up .
if not.......,
excessive B+ may have elevated secondary supplies on flyback , leading to failure of vert output ic.
continued operation likely toasted the hot.
additional damage possible in smps , but check hot 1st.
it will likely be shorted 


qrz

[MK3FAN]

i hope u matched the pot to the fixed resistance before pwr up .
if not.......,
excessive B+ may have elevated secondary supplies on flyback , leading to failure of vert output ic.
continued operation likely toasted the hot.
additional damage possible in smps , but check hot 1st.
it will likely be shorted 


qrz

Thanks. Good thing I recently bought 5 of them. Before I turned the chassis on, I had the pot all the way down. I'll check the HOT. EDIT...The HOT IS indeed shorted. I'll change it out really quick and see what happens.

[MK3FAN]

The HOT replacement got it up and running again, but the picture is the same as it was before I replaced the flyback and the cap kit. Neither one made any difference in the problems I am having. When I adjust the Horizontal Hold to where the picture stops shaking, I get a huge gap to the left and the screen is cut off. Adjusting the Horizontal Position makes no difference.





If I tweak the Horizontal Hold all the way to the left, the image fills the screen like it should but it's completely fuzzy and wavy. The focus pot on the flyback works normally. Any ideas?

[qrz]

near the la7850,
check c706,9 (1uf/50v) c602 or is it 802 ?? can't make out print  ( 10uf/50)
c605 or 805 ?  (100uf/35v)

the h-pos pot has no effect ??

qrz

[MK3FAN]

near the la7850,
check c706,9 (1uf/50v) c602 or is it 802 ?? can't make out print  ( 10uf/50)
c605 or 805 ?  (100uf/35v)

the h-pos pot has no effect ??

qrz

Thanks. I'll check those caps. When I move the Horizontal Position pot, the image shakes a bit, but it does not move it left or right. When I adjust the Horizontal Hold, the image moves left and right as if it were the Horizontal Position.

[SirPeale]

Is this an actual MK board or Mame?

[MK3FAN]

Is this an actual MK board or Mame?

Real MK. This is not the monitor from the MK2 cab that it's next to. This is an extra monitor that I am using the MK2 cab to test it with. There is nothing wrong at all when I hook the cab's monitor back up. It's not the cab, or the game, or the wiring. It's something wrong witht he chassis.

[MK3FAN]

near the la7850,
check c706,9 (1uf/50v) c602 or is it 802 ?? can't make out print  ( 10uf/50)
c605 or 805 ?  (100uf/35v)

the h-pos pot has no effect ??

qrz

Well, I changed out all those caps and still nothing. I think I am going to abandon this project as I really never needed this chassis in the first place. It was just included in a recent cab purchase that I bought just for the cab and not the monitor. I was told it just needed a couple caps, but obviously not.

[qrz]

for what it is worth ......
if u have a osciliscope, u might wish to have a look at the h drive out from the la7850.
i have seen a few with distorted waveforms.....


qrz

[Kevin Mullins]

Plug something else into it and see if the image does the same thing. 

Since you've stated it's a U5000, I assume it's the dual resolution?
Just verifying.....a lot of chassis were based on the same main chassis.

[MonMotha]

MK2 does run with somewhat unusual video timings.  It's like 15.5kHz/53Hz (more lines of video than most standard res games but a lower refresh rate to bring it back down to 15kHz).  Not sure of the implications of that here, but it might help somebody else out.

I almost wonder if that's a positive/negative sync issue.

MK2 also does have separate sync available on the connector near the side of the board.  Perhaps attempt to use that separate sync.  If it works that way, might be useful info as well.

[MK3FAN]

The chassis IS dual resolution (15/25Khz) but it's set to 15, so that's not the issue. I have access to an oscilloscope, but not until Monday. The image looks perfect when I use the monitor in the cabinet, but when I hook the input to the U5000, it's like the above pics. Also, the problem I am experiencing is exactly the same as it was before I did the cap kit/flyback replacement. That leads me to believe it's a component failure of some type other than the normal ones. Also, the chassis does not charge/discharge the tube. Under normal circumstances, when you power on a chassis, you will hear the flyback charge up the tube. When you shut it off, you hear the tube dissipate some of that charge. This chassis does none of that. You don't hear the tube do anything when the chassis is turned on OR off. When you turn it on, the image simply appears with no "charge up" sound. I've never run into that before.