25" WG K7000 has Raster but no Picture

[Buffett]

yea

yea game play's blind i have had on the test bench and in a game same thing no pic just scan lines. ill get back to it in a week or two and see if its somthing i missed in the cap job or a bridged solder point or what ever then ill send it to a pro to get done if i cant get it going. i am learing alot from all the help on here and have fixed several from the dead because of this wonderful place and its members.

Peace
Buffett

 

[sohchx]

. i am learing alot from all the help on here and have fixed several from the dead because of this wonderful place and its members.

Peace
Buffett

X2!!!! I don't think I would even be in the hobby anymore if it were'nt for the guys here or the forum threads for their wealth of information. I have had help resurecting many games from the guys here

 

[DaveHanes]

Sorry to resurrect this old thread. I hadn't noticed all of the later responses. I set my bad chassis aside, as I never could get it to work.

In my case it's definitely related to the chassis, as I plugged in a different chassis and it worked fine, so the CRT, gameboard, and power supply are ok.

If anyone wants to take a look at it, let me know. I would be *more* than happy to send it off!

Thanks!
Dave

 

[Buffett]

i did get mine fixed a little wile back

i did get mine fixed a little wile back around 3 months or so ago.

I don't know what exactly fixed it but i went to town on solder joints. i did a full cap job. filter cap and all the bipolar caps. and made sure i did not bridge any solder joints. hooked it back up and it worked. only use the last pin in the three pin header for sync.

what i did not like about this model is its a pain to make look rite. so i put it in a box. and if needed i will use it for a spare. other wise it's for sale as i don't really want it. none of my games need all that kind of adjustment.

so if any body wants to buy it for their game it's for sale.

i would be happy to look at it for you if you want just send me a pm.

Peace
Buffett

 

[modessitt]

Wanted to add another fix to this thread:

I recently rebuilt a K7000 that gave me raster but no picture. I tried swapping out IC1, installing new BP caps, swapping neckboards, swapping flybacks, checking the 12v, heater voltage etc - but still no picture. Just a glow on the screen when I turned the brightness all the way up.

So, I was reading in the manual about the video processing, and saw a mention of a gate off of IC2 Pin 12 that was necessary for IC1 to pass the video signal through. I checked the voltage at IC2 pin 12. What was supposed to be 1.3vdc was in fact 10.8vdc. A look at the chip layout showed that the 1.3 was dependent on an input of 13.7vdc on Pin 14, which was correct. That lead me to believe that the problem was internal to the chip, so I replaced IC2. My picture is now up properly.

Hope this helps someone...

 

[kdoe]

Just to add another issue/fix I have just come across with a 25" K7000a

No picture but if you maxed out contrast, black level and cranked the screen up you could just about see something amongst the restrace lines.

I tried most of the fixes already mentioned but no luck. I indentified an issue across Q8, which was giving some incorrect values (Base was -7 volts and the Emitter was virtually 0v). The tranisstor tested good though I replaced it anyway. The actual fault was R95 (47K) which read a high resistance and R94 which was open circuit.

 

[thrillhouse900]

Sorry to resurrect an old thread. But I was having this issue. Solved by switching the sync from Horiz+ to Horiz- on the chassis board. Doh!!!!

 

[Dr. Willy]

bumping this due to having the same issue. IC1 fixed it for me.

 

[AnthonyGK]

Fixed one thanks to this thread. It was a lack of +12VDC, which IC1 and IC2 require to generate RGB and sync signals. Easiest place to check for it while powered up was on the back of the neck board. I probed the trace that runs to the lower-left pin of cutoff pots VR201, VR203 and VR205.

Cause was R92 being installed but loose, with no solder. Soldering it restored +12V and my picture. Thanks to everyone who contributed to this thread!