broken v hold pot?

[mitch]

i bought a "working" k7000A chassis from a guy on ebay who had done some scary looking "repairs" on the board.  from what i've read in the forums i think my main problem is a broken v hold pot.  when its turned one way there is nothing on screen, turned the other way a flickering, folded image starts to drop down from the top. the image stops half way down the screen and the bottom of it is a very bright line. in my case the line is bright blue, i did some poking and found my blue drive pot was broken (both of these pots were among the "repairs" done to the boards). the pot turns around completely and does not stop, obviously needs replacing.  i'm going to pull the v hold pot out of the board, clean up any mess and put it back in. if that goes nowhere i guess i'm waiting till parts arrive.  i had already planned on buying cap kits, and all new pots for the chassis and neck boards on both my k7000's. i was also thinking of wiring up front bords for my drive and cut off pots. thoughts or suggestions?


here is a picture of the chassis in question displaying a CPS2 Alien vs Predator. i also have hi res shots of the chassis and neck boards if anyone wants to see them.

[Ken Layton]

There is nothing wrong on the bottom (foil) solder side of the boards. That is the typical Wells-Gardner factory soldering job. Those parts and wires were put there by the factory and are UNDOCUMENTED! Leave those parts alone.

First thing you should do is install a capkit. Buy the vertical output integrated circuit too because it's a strong possibilty that yours could be bad. Wells used 5 different type number chips for the vertical output and you need to replace like-with-like numbers. It is attached to that giant vertical metal bracket next to the main filter capacitor.

All the pots on the main board are delicate and can break easily during shipment. Bob Roberts sells all the pots for these monitors.

I strongly advise against moving any of the pots from the neckboard. High voltages are involved there. Just replace any broken ones.

[4nic8tor]

http://therealbobroberts.net/pots.html

I bought one there for 3 bucks and 6 for shipping.  Hey Ken, on the topic of the undocumented wires...My K7197 had a black wire from the main ground on the underside of the board (the metal piece that the HOT is connected to) to one of the caps I replaced with the capkit.  I did a continuity test with my multimeter and it has connection to ground even without the wire.  So I figured someone added it during a hit and miss repair job and I just left it off.  It has good connection to ground and it is working great, is that wire really necessary?  It's almost just like the black wire in his pic above...

[Ken Layton]

Yes that black wire was put there by the Wells-Gardner factory. They found that after the k7000 series went into full production there was a problem with a ground connection (cracking in the foil breaking the ground connection) in the horizontal output section. That wire was put in the circuit so the ground connection wouldn't be lost in the event of hairline cracks developing in the foil.

 

[mitch]

THAT is a factory repair job? wow, i didnt expect to hear that! the vertical output is IC3 correct? does bob sell the vertical output IC's as well? and do you think that the IC is more likely the problem rather than the pot?

[mitch]

and hey, since we're on the topic of k7000's, i have an area 51 game board that i cant get to display properly.  the area 51 manual says it needs:

color RGB monitor, seperate positive horizontal and vertical sync or negative composite sync, horizontal frequency 15.750 khz, vertical frequency 60 hz, video input 1v to 3v peak to peak positive polarity. unless i'm missing something in my ghetto printed manual, the k7000 fits that decription. however, on the wells gardner website they have a game/monitor cross reference section.  they list a wgm2574 - u4gs55h as the monitor used, and a wgm2474 - u4ts16q as the current choice for area 51. are my k7000's not compatible with this game board? when its powered up i can see the demo running, but the image is really skewed and waving all over the place, there is no way i could play it.  i only have the game board and hard drive, i dont yet have a set of guns, nor do i have the "electronics assembly tray" the pcb and hard drive are meant to be mounted to. i dont know if its a problem with the game board not being properly grounded or ifs just something dumb that i cant figure out cuz i'm new.

[Ken Layton]

THAT is a factory repair job? wow, i didnt expect to hear that! the vertical output is IC3 correct? does bob sell the vertical output IC's as well? and do you think that the IC is more likely the problem rather than the pot?

Yes that is indeed a factory job! That's why some people complain about poor quality from Wells-Gardner.

Vertical output IC is indeed IC3 on the board. Only install a like numbered part:

UPC1378 or NTE 1676

LA7831

LA7833

AN5515

[Ken Layton]

and hey, since we're on the topic of k7000's, i have an area 51 game board that i cant get to display properly.  the area 51 manual says it needs:

color RGB monitor, seperate positive horizontal and vertical sync or negative composite sync, horizontal frequency 15.750 khz, vertical frequency 60 hz, video input 1v to 3v peak to peak positive polarity. unless i'm missing something in my ghetto printed manual, the k7000 fits that decription. however, on the wells gardner website they have a game/monitor cross reference section.  they list a wgm2574 - u4gs55h as the monitor used, and a wgm2474 - u4ts16q as the current choice for area 51. are my k7000's not compatible with this game board? when its powered up i can see the demo running, but the image is really skewed and waving all over the place, there is no way i could play it.  i only have the game board and hard drive, i dont yet have a set of guns, nor do i have the "electronics assembly tray" the pcb and hard drive are meant to be mounted to. i dont know if its a problem with the game board not being properly grounded or ifs just something dumb that i cant figure out cuz i'm new.

Those monitor specs are just there to confuse you. Area 51 is Jamma standard and as such puts out a composite negative sync signal usuable by just about any monitor. Only the dedicated Area 51's came with 25" monitors like the 25K7400 mentioned in your quote. Area 51 was also released as a conversion kit. I built dozens of Area 51's. Most had 19" monitors. I've had it running on Wells k4600, K4900, and k7000 series monitors with no problems at all.

Be sure your monitor is connected properly, it's had a recent capkit, and the game power supply is set correctly. This board set likes to work best at 5.2 volts (as measured on the board). Lower game power supply voltages can sometimes give the symptoms you talk about on your monitor. I seem to recall Atari issuing a service bulletin about that.

The "electronics tray" is just a fancy term for the big piece of sheet metal Atari bolted the board and hard drive to. The sheet metal had ½" high threaded metal stand-offs staked into it for the board to bolt to and to raise it for ventilation (it runs hot).

[mitch]

still cant get this area 51 figured out, me and my roommate have spent the last couple hours playing with the v and h holds and positions, voltage knob on the power supply, the only things we havnt turned are the h width coil and the bottom knob on the flyback wich has been hot glued in place apparently. i'm out of ideas so in a last ditch effort i have taken a quick video clip of the game playing through its demo mode and posted it online.  can somebody please take a look at this and hopefully tell me whats wrong.  the color is way off and you cant make out much from the video, but hopefully the "pattern of madness" will lend some insight as to what the problem is.  here is the link

http://www.vidilife.com/video_play_971751_best_i_can_get_on_a_WGK7000.htm

[Ken Layton]

Sorry I can't run videos on my computer. Not enough memory, plus my Real One & Windows Media Player have corrupted files. And I'm on dialup.

[FrizzleFried]

Damn...that looks out of sync...but I'm not the expert...

Someone donate Ken a computer and a high-speed connection!

[mitch]

here's a picture of the screen playing through the area 51 demo. the monitor was displaying my cps2 perfectly, i swapped the area 51 board in and this is what it looks like.

[Ken Layton]

Did you adjust the "horizontal hold" control yet?

[mitch]

yeah, i adjusted the h hold, and it does at least bring some picture through, i can make out characters and text and the like. but the picture wont sit still, and the image is split vertically down the middle. what should be on the left side of the screen shows up on the right and what should be on the right is on the left. but in the middle of the screen is black.