Newbie needs advice on a 25K7000 dead chassis

[Oryk Zinyo]

The white know flybacks are prone to cracking and the resulting arc can damage anything including someone adjusting the pic. I always replace old K7000 flybacks.

I always socket IC1 and IC2 when I swap them out. It makes it easier to continue troubleshooting if the initial swap doesn't fix the problem.

 

[Teknotoyz]

The white knob flybacks are prone to cracking and the resulting arc can damage anything including someone adjusting the pic. I always replace old K7000 flybacks.

I always socket IC1 and IC2 when I swap them out. It makes it easier to continue troubleshooting if the initial swap doesn't fix the problem.

I have a black knob flyback I removed during the shotgun fix of this chassis, likely still good.
Is it worth installing a used fly? In many ways I hate taking a working one out, but everyone is pretty consistent in saying these white knob ones fail in a spectacular and destructive manner. My BR order arrives tomorrow, hopefully the Q2 & Q3 are bad, easier fix than the IC1.

 

[Oryk Zinyo]

I have seen the black knob flybacks fail as well. It is really only a matter of time, from what I have seen they appear to overheat with use, causing the casing to get brittle and then it cracks. Once the insulation cracks then the fireworks begin. Personally, I would just install a new flyback but depending on use the old fly could suffice.

 

[cadillacman]

whos aaron???

 

[cadillacman]

I have a black knob flyback I removed during the shotgun fix of this chassis, likely still good.
Is it worth installing a used fly? In many ways I hate taking a working one out, but everyone is pretty consistent in saying these white knob ones fail in a spectacular and destructive manner. My BR order arrives tomorrow, hopefully the Q2 & Q3 are bad, easier fix than the IC1.

i prefer used only if its a game im dumping or some kraptastic turd not worthy of a new fly.

the other bonus would be keeping thr used fly around for emergencies etc.

for $30, its cheap insurance to just replace the damn thing. DO it, get it over with, dont worry about it for another 20-30 years.

on your chassis with color issues make sure the blue and white wires harness between the neckboard and chassis is ok, and check both ends for cold solder. If one or more wires is broken, you can be missing some colors.

Im proud of you man, goin for it head first. Once you get a couple of these damn things under your belt they really wont seem so bad.

 

[modessitt]

If the old flyback works and shows NO cracks around the knobs, then go ahead and use it. If you see even a tiny crack, replace it...

 

[Teknotoyz]

OK, did some work tonight.
I found a broken solder pad on the neck board, blue transistor.
It appears that I was right about red being the only color.
Now blue has joined the fun..... but no green.

Crap, swapped the chassis back out and.... crap, no green with the other one either.
It would appear the tube is possibly faulty, didn't notice as I was too taken by the blue skies.
I need to double check the pins on the tube to make sure they are all there.

Any ideas? I need to get my other chassis capped and get my Neo Geo back together to see if the green is working there, should be, never noticed an issue on the NG.
I did check the Jamma Harness and the green input is good from connector to monitor (2.5 ohms), also swapped out a PCB to make sure it wasn't faulty.
If the speaker magnet gets near the tube, I did see some green distortion... is this any type of indicator?

Damn Damn, I do have another 25" tube, but the yoke appears to be no match for a K7000.
Just how hard is a yoke swap?

 

[modessitt]

It's easier to find someone with a rejuvenator to check your tube. Or try grounding the tab of your green drive transistor to see if the screen goes all green.

And sometimes the green goes out on my test bench harness even though the tube is good. Usually it's a connection issue. Have you reflowed the video header?

 

[Teknotoyz]

Or try grounding the tab of your green drive transistor to see if the screen goes all green.

Your talking the tabs of the transistors on the neck board?

 

[KevinMullins]

Your talking the tabs of the transistors on the neck board?

The metal thingy sticking up from the back of the drive transistor.
(where other similar transistors would be mounted to a heatsink)

Definitely check your video input header pins like Mod said, check the video harness, etc, etc.
Any time I troubleshoot a missing color, I start with knowing for sure I have that color coming IN.

 

[Teknotoyz]

Definitely check your video input header pins like Mod said, check the video harness, etc, etc.

Very good advice, I'm gonna drop a different, known good, monitor in and confirm the cabinet wiring is OK (or not).

If the old flyback works and shows NO cracks around the knobs, then go ahead and use it. If you see even a tiny crack, replace it...

Uh, yea, you nailed that one. One wipe of a rag and no doubt it won't work. I feel a lot better about replacing it now!!!

More to come, but a quick recap on what you guys have helped me with:
-Bad flyback
-Shorted C38
-Bad HOT
-Broken trace on the neckboard
-Installed a cap kit

Green still MIA
Image looks good otherwise, but the camera didn't take a good picture with the fast moving graphics.

 

[Teknotoyz]

I'm proud of you man, goin for it head first. Once you get a couple of these damn things under your belt they really wont seem so bad.

Thanks! I definately feel like I passed the newb checkpoint. I can now say I brought a K7000 back from the dead to 100% working.
(with help of course!)


Well, it appears this job is done. Same chassis and cabinet, changed the tube, and green is working.

It's a shame, the tube is a sour ending. I'm putting the newly rebuilt chassis into the Neo Geo cabinet which solves my flyback issue there.

One final question, is there anything a person can do to help a tube without a rejuve?

If not, to the trash for this tube and I will attempt a yoke swap with another 25" tube I saved from the dumpster a while ago.

The picture is 1000% better with green working BTW!!!

 

[cadillacman]

you can go old school... with it on crank the green gain to max, rapidly tap the back of the tube in the neck/gun area machine gun stlye hard enough to try to loosen krap up but not so hard if breaks the neck.. hold the screwdriver backwards basically, think of it like a drum stick... and tap on the neck at a 90 degree angle to the neck,


worst case, you neck a junk tube. Best case, it works.

 

[Teknotoyz]

you can go old school... with it on crank the green gain to max, rapidly tap the back of the tube in the neck/gun area machine gun stlye hard enough to try to loosen krap up but not so hard if breaks the neck.. hold the screwdriver backwards basically, think of it like a drum stick... and tap on the neck at a 90 degree angle to the neck,


worst case, you neck a junk tube. Best case, it works.

I thought this was an ol' wives tale.....
Well, nothing to loose, so it was hammertime.... screwdriver handle hammer that is...
I tapped and tapped and nothing... tapped HARD... turned and looked and GREEN was all over the screen!

IT WORKED!!!! WooHoo, Another monitor saved!!
I guess I take back the sour ending... All is well with this job.


Cadillacman, your a....

 

[cadillacman]

MUWAHAHAHAAAA there ya go,

I think i learned that trick from mod or kenlayton bitd...

Has this experience made you wish you had a rejuvenator?

honestly i got mine cheap, like $75.... was well worth it to take away some guesswork.


time will tell if it lasts, but hey what the hell...

 

[Teknotoyz]

Has this experience made you wish you had a rejuvenator?

honestly i got mine cheap, like $75.... was well worth it to take away some guesswork.

Yea, already looked to see what's out there. I'm mainly afraid to know what tube adaptors should be with any given unit. May buy something, but will need to ask for help in selecting a good deal.

Thanks again!

 

[KevinMullins]

Sweet job!!
Typically I use the "tapping" trick for clearing a shorted color gun when a color is stuck full on/can't turn it down. (that is when I don't have my rejuvinator handy)
Nice to see it resurrect a missing color as well.

 

[Teknotoyz]

Well, green gun has died again.

Gonna try a tube swap for the heck of it. The Dynamo cab is lookin like it's gonna get parted out if I fail.

 

[R3LL1K]

Well, green gun has died again.

Gonna try a tube swap for the heck of it. The Dynamo cab is lookin like it's gonna get parted out if I fail.

I'm sure you can find an old 25" tv to steal a tube from can't you?

 

[Teknotoyz]

I'm sure you can find an old 25" tv to steal a tube from can't you?

I have an arcade tube I can try.
Never done a yoke swap yet though.