Wells K7171: what happens when you don't replace white knob flyback (oops)

mecha

Well-known member
Joined
Apr 19, 2007
Messages
24,331
Reaction score
7,036
Location
MKE, Wisconsin
Wells K7171: what happens when you don't replace white knob flyback (oops)

this was awesome.

ec6b59c5fd2b.jpg


observe the awesome hole where the C36 is. I tried scraping the char marks off and wound up poking straight through the board through the other side.

726d69a42803.jpg


so aside from the flyback being trashed (no oozing or cracks that I've noticed), the HOT being fried, the C36 having char marks underneath it and the IC4 being nuked, am I supposed to jumper those traces for the C36 cap that are like non-existent now with diode wire in addition to doing that mod that's on Bob's page?

and is there anything else I should test for or should I wait until I see what happens when I get the parts in?

also, is what happened here what normally happens when people oblivious to burning smells and blank screens allow this to happen for over 30 minutes? ironically I was across the way replacing my first flyback on a K7500 while this was happening. I should go to Vegas with those kinds of odds.

oh yeah, I should be the spokesperson for the "Save the K7000s" foundation. raised awareness for white knob flyback replacements, you see.
 
Last edited:
I'm surprised it didn't short the Hot eventually and blow the fuse, saving you a bunch of solder work.

Man, you've got to save it. Then you'll have something to brag about. You can go

"Yeah, that bitch caught on fire, burnt a hole through the board. 'Course I fixed it"
 
yeah, the fuse LOOKS intact, I didn't meter it, but it doesn't look like it's blown to smithereens. so are the usual 4 parts all bad you think? the cap actually didn't explode or anything, doesn't look bulged, just was fried on the one side.

I hate that I have to order this stuff through Bob, have to look up everything and get an e-mail quote, send a check, etc. then wait. heh
 
Even with Bob's process, he's still fast as hell. I don't think I've waited longer than 2 or 3 hours to get my order confirmed.
 
I'm going through Bob. he had a shitload of parts and kits that I needed. and his prices are substantially less.

I might resurrect this thread for assistance. am I correct in understanding that those traces that are fried going to the CSC are pretty much done and I can get away with jumpering them with some excess diode wire? like does the trace width matter (how much wire material I throw at it)?
 
I'm surprised it didn't short the Hot eventually and blow the fuse, saving you a bunch of solder work.

This goes back to the discussion you and I were having the other day about the G07 fuse F901. Don't have the K7000 schematic in front of me, but IIRC the K7000's are just like the K4900's in that there is no fuse except the main 120V fuse (F501 - F902 in a G07). In my K4915, the HOT will short to chassis and turn the main power resistor into a space heater without blowing F501...

I've since decided to add a fuse on the B+ line between the power supply and the primary HV winding.
 
well, I had some downtime to bring out the dead while I'm waiting for the parts from Bob. I don't know entirely how to meter HOTs and VRs for shorts, but I was getting some readings across certain legs on them, does that mean they're not shorted?

it's looking like the C36 absorbed most of the damage, as evident by the disintegrated traces. I haven't jumpered those yet, I have to wait until I get the new components in before I try that, but it's looking like the red pin on the yoke header took a bit of a beating too (I changed out the yoke connector with parts from some Wells 3331 junk chassis I had laying around) ... would this have affected the yoke at all?

Bob told me to scrape out all the charred stuff, and I think this is about as good as I'm going to get it, cause if I probe any further I'll have an even larger hole and there's gonna be a lot of wires touching each other. I'll get new pics in a bit.

I re-capped the monitor as well. the C204 on the neckboard has one of those orange blisterpack looking caps in it now... do you just leave that in there and not replace it?
 
oh, as previously mentioned, I think, I didn't check the fuse before.

I did today. thank you Bob for including a new one. the old one was visually fucked.

I ran comparisons on the old HOT and VR to the new ones, they're definitely shorted. and the C36 wouldn't ohm out at all. and although the old flyback didn't have any goo oozing out of it, there were some very subtle cracks around the focus pot.

I will keep them all for use in a collage someday.

all the dead traces were jumpered using wire from diodes. as per Bob's instructions you also have to make some jumpers on C36, since the replacement doesn't have 4 legs. I used Ceramique for thermal paste. other than that, I had to take half the damn thing apart to get at the parts that I needed to replace, so all in all, I think the total work time (in-between doing my ordinary service calls in the game room) was around 2.5 hours. (including the cap job)

I'll be in need of a new C38, which I'll just get from Happ with the other parts I need for the other games, cause the width coil is non-responsive.

now I have 5 more monitors to re-cap. there's not enough drugs in the world for what's in store with all that Nintendo shit, since I have to take each monitor out.
 
ahoy. I didn't think it should. I think it's what cadillacman asked me to do though. but it doesn't matter, I got a new one in it.

does anyone know why I have 3 faint vertical lines spaced about an inch and a half apart from the left part of the screen? it used to be just 1 prior to the cap job. my width coil is non-responsive, and C38 looks pretty messed up, does that have anything to do with the vertical lines?
 
On a related note, what is the best way to attach the red wire that goes to the neck board? Most K7000 flybacks I've ever had to replace don't come with that grey connector attached so I've had to splice the new wire to the old (solder and heat shrink tubing of course), or use a female molex pin and those seem to fit well. I've never had much luck trying to de-pin the original. Bob's flybacks I know don't come with them.
 
I seriously just hardwired the K7500 and K7000 I've done recently. if anyone can tell me how to do it differently, speak up. :)
 
Back
Top Bottom