Big Mike's K7000 repair tips

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****This info is posted assuming you know how to solder, know how to use a meter, and know how to properly dischagre a monitor. If you do not know any of the things i just said, get on youtube or a simular site and educate yourself before you attempt any monitor repair*****

Hey guys... i figured id talk a little about some common issues ive come across with the wells gardner 13k7000's, 19k7000's and 25k7000's. 80% of this info does not apply to the newer 7400 and 7500 series.

There seems to be alot of common issues with these older wells gardner k7000 monitors and i figured i would take a little time to discuss these issues. Im no "expert" but living around chicago i ran across these monitors alot so i figured i better share what ive learned myself and what ive learned from other forum members.

SCREEN ISSUES???The first one is screen collapse or a lightning bolt effect if the monitor chassis is tapped on. There are varying degrees of this, but its something that usually changes with monitor run time.. There are a few larger resistors in the r98-r101 area. Do yourself a huge favor and unsolder and resolder those. Sometimes r101 runs so ho it changes value. Another issue is sometimes r101 traces will fry, or will tarnish black. You wont see this unless you UNSOLDER then inspect the trace pads.(its amazing how fried they get sometimes) Be sure to pull and ohm test r101 as sometimes it will actually change value due to running so hot. Sometimes you will get screen weirdness/jittering accompanied by a arcing sound. This is usually the flyback arcing out or the red anode lead arcing out. In either case, replace the flyback!

There have been noted cases (but i have not verified) of C51 going bad causing screen size issues or in extreme cases screen collapse. C51 is a "dipped tantalum" electrolytic capacitor and it is NOT INCLUDED in any cap kit. Youll have to find it from bob or mouser, etc

SOLDER::These monitors(like any other 30 year old piece of electronic equip.) also develop bad solder connections. It will look as if there is a circular crack or ring in the solder joint. This can vary from screaming obious to barely noticable. On the wells monitors, these tend be prevalant in the area of large resistors/components, yoke connector pins, power diodes, and ***the video input pins**** Cracked solder at the input pins can cause intermittent color loss or intermittent rolling issues/jumping..

FLYBACK ISSUES:Some of these monitors have a very common flyback failure rate. Theres two different flybacks used on these monitors apparently. Both interchange, but i have seen a difference. The older monitors tend to run a flyback with white adjustment knobs. This flyback totally sucks. The plastic casing will literally fall apart in your hand and they tend to crack alot. If you come across one, REPLACE IT NOW whether the monitor works or not! The other fly is all black. Look it over well. If you see a yellow goo bubbling out of the seams, its bad or going bad. Look them over very well for cracks. Find a crack? REPLACE IT... they arent much money,and replacing a cracked fly on a working monitor will save you alot of money in the long run. Here we see the yellow "goo" coming out of the right side seam of this flyback. This flyback is toast.

SHUTDOWN:Ok , heres our worst case senario. You have a monitor thats just dead. Heres some basics to start. CHECK POWER: do you have 110vac power at the power connector to the monitor? CHECK FUSES: is the fuse on the chassis blown? CHECK FUSE HOLDER: sometimes these will get weak and lose contact/tension, or the fingers will literally fall off. VISUAL CHECK: check the chassis over well for cold cracked solder joints, check the flyback for cracks, check the chassis for cracked traces, check for bulged caps, etc. DO you have screen "static"? do you have neck glow??? if so, you have some sdigns of life. Turn up the "screen" control on the flyback just got gigs... sometimes you get lucky and some a-hole turned down the screne knob at some point....

CHASSIS FUSE BLOWN??? Check the hot(horizontal output transistor) ohm in between the center and third pin... if you read anywhere near 0 ohms, its shorted.(pull; and retest to make sure) If the hot is shorted, theres a reason it failed... usually a flyback failure. In this case replace the flyback, hot,fuse, and VOLTAGE REGULATOR. WHen the hot fails, if usually takes out the voltage regulator too. There is also a saftey cap, c36, that will sometimes short out, especially if youve had a hot of flyback failure.. Ohm it out one meter lead at each end.(if you have the 4 legged cap this test still works, just pick one leg on each side) Replace this cap if shorted. I have also heard about the large diodes shorting out, but ive never seen it personally***STILL WORTH YOUR TIME TO CHECK THESE***

CHASSIS FUSE NOT BLOWN BUT STILL IN SHUTDOWN?This could be a blessing or a curse. If the fuse is good, this could be a simple fix. FIrst things first make sure you have power input. Visually check the shutdown pot to make sure its not broken. Visually check over solder connections. I have seen capacitors next to the shutdown pot get so dried out that the monitor shut down. Replacing just those caps fixed it, but i went ahead and recapped the monitor anyways. If you have a real grimy monitor chassis then mark the position of the shutdown pot knob. Move it back and fourth using pliers or a simular tool, then reset it to where you made your marks.. I have seen that pot be so dirty that it caused shutdown. Ive also seen v-regs cause shutdown, especially if its already been worked on and the folks did a fly and hot but never replaced the v-reg.

INTERMITTENT COLORS: :Have seen this happen form time to time... Sometimes you get lucky and its just a cold solder joint somewhere(usually around the video input pins or on the neckboard). However if your one of the unlucky folks to get a color that sticks on all the time or after warmup, then you may not be so lucky. Try swapping the drive transistor of the offending color to a color that works. Same for the pots. No change? most likely you have a shorted gun in the tube. This can be diagnosed and sometimes repaired with a rejuvenator. Make buddies with a guy that has one heh... I should also note that ive ran into uneven brightness issues. It looked like vertical jailbars but it was just like uneven contrast, worst on the left side for some reason. Replacing a few of the large caps near the flyback fixed it, but i went ahead and did a full capkit anyways.

POTS POTS POTS For some reason, wells used these ceramic backed adjustment pots. They wear out easy, and crack VERY easily. If you are having a issue with rolling, brightness, color, whatever, LOOK THE POTS OVER WELL. Ive missed a cracked pot a few times and wasted alot of time before i figured it out. If you have the wells monitor with remote board that has broken pots, you can get pots from bob roberts(www.therealbobroberts.net), or for just about the same price, you can get a brand new remote board assy from chad over at arcade cup (www.arcade-cup.com)

Left the crt to neckboard ground off??Well thats a bummer! Without that ground itll try to arc and spark to ground anyway it can. I recently had one that i replaced the hot and vreg, got it to run finally however the pic was very skewed. It did not sync well and the pic was crooked and half off of the screen. I replaced ic2 (vert/horiz ic) per ken laytons suggestion and that cured my issue!

PARTS RESOURCES: www.therealbobroberts.net-- bob is a ex op whos retired,. He sells arcade parts to the general public, prices are good, and if you do repeat business with him and establish a friendship, he will usually cross ship our stuff which is neat.
www.arcadecup.com chad over there in green bay, wi repeirs monitor chassis for those who cant fix them themselves. He has a decent turnaround time and fair prices. He also sells new and used monitor parts.
www.ebay.com-- suprisingly you can find great deals on fleabay from time to time.. sometimes you get lucky and find a tub of nos transistors for like $4 or something...
www.mouser.com, www.digikey.com, www.bdent.com, www.future-electronics.com all sellers of replacement electronic components..

Well i guess thats all for now. I will continually edit this post with YOUR input untill i feel its done. KEEP EM GOING!!!!