K7000 Oddity

Azure Oz2 said:
Those solder joints don't come up looking great in the photo, could be the light or camera angle.
To help confirm and narrow the fault to chassis or yoke/wiring, take your yoke resistance measurements on the chassis at a point where the yoke connector pins go to, not directly on the yoke connector pin. Take a reading with and without yoke connected. If reading with it connected is close to out of circuit reading then the problem is in the chassis somewhere.

Looking at the chassis side on the schematic R96 looks like the only part that could stop horizontal output and not effect the EHT (which is also driven by the HOT - which is why we know it is ok). Check that R96 resistor and the solder joints.
Click to expand...
I'm aligned.

I see problem connections needing reflow in the red circled areas.

1689907115971.png
 
Infa Red said:
Ok, got a report. I think I found 2 possible culprits to the issue. Not sure which one is the cause, but will be fixing them both regardless. First off I reflowed the Yoke pins, and everywhere else I seen issues. So thats done. Also I checked the points @M K L suggested and I believe its ok, it was not infinite for sure, but kept dancing between 1.5 and 4 ohm... something like that. Though I'd see a occasional spike to about 70 ! lol Either way, its reading something so hoping that = ok.

The first issue I found is not bad news, easy fix. When I was lightly pulling on one of the yoke wires (and I mean really lightly) it broke off from the pin inside the molex connector.. so I swear it had to be barely attached. The wire looked severed at the crimp area. I have to order some pins to fix that and I'm just gonna do them all while doing it. The wire that it was was part of the lower number side, 4Ω side, which might be a hint to if it was the problem so I wanted to mention that. I just forget which is horizontal and which is vertical. The yoke is a 15Ω/4Ω yoke, the 4Ω side was the one with the break.

But here is the bad news, the 2nd issue, hard to fix. R96 was soldered good, solder was fine, part tests fine, but it was wiggling and I noticed some movement. Upon closer inspection BOTH pads are lifting up from the board :-(. That said, it technically was still connected solidly to the copper pad even when moving so in theory should not have been a issue. But it very well might be. I took it out and lifted them up so you could see them good in a pic.

I remember seeing someone be able to fix these good, but I forget the technique. Could anyone share the best technique how I can fix these to be the best they can be again ?

View attachment 678581

And here I want to show how when its soldered good and solid, it does lift, yes, but in theory its got a solid connection to the copper, so is this a problem even ? Should I just leave it ?

View attachment 678582
Click to expand...
Super glue and press down. Or epoxy.
 
Infa Red said:
Got you ! Will do, and thanks for pointing them out.


Really ? Its that easy ? I imagine you mean solder first, then once cool glue down. BUT - Wont soldering/desoldering down the road years later melt the glue or do they make a high temp epoxy ?
Click to expand...
No, super glue, glue it down FIRST, then solder. Or epoxy.
 
Same question as @Infa Red: Super Glue (say Gorilla super glue) will hold up to the heat??? There is a trace lifting on my K7 around R101 and disregarded Super Glue / Epoxy since I was sure it would just melt away. Glad you asked about this @Infa Red because this has been on my mind!
 
I am thinking there has to be a special PCB Epoxy for this (extreme high heat tolerant, non-conductive, etc..), its too popular of a problem.
ArcadeTechGW said:
No, super glue, glue it down FIRST, then solder. Or epoxy.
Click to expand...
This is amazing. I am in disbelief, lol

So you are saying super glue holds up to the 700º temps and stays glued down ?

Odie3 said:
Glad you asked about this @Infa Red because this has been on my mind!
Click to expand...
So pending on the exact situation, another option I was thinking is,,, maybe... is to bend the lead leg over so it reaches a solid part of the pad/trace, scrape it down to expose the copper and then solder the leg to that. ?? But the situation needs to allow for that of course.

If the leg isn't long enough you can solder a extension on it. (I am thinking)..
 
Infa Red said:
I am thinking there has to be a special PCB Epoxy for this (extreme high heat tolerant, non-conductive, etc..), its too popular of a problem.

This is amazing. I am in disbelief, lol

So you are saying super glue holds up to the 700º temps and stays glued down ?


So pending on the exact situation, another option I was thinking is,,, maybe... is to bend the lead leg over so it reaches a solid part of the pad/trace, scrape it down to expose the copper and then solder the leg to that. ?? But the situation needs to allow for that of course.

If the leg isn't long enough you can solder an extension on it. (I am thinking)..
Click to expand...
The board doesn't hit 700 Deg F. It's a fraction of that.
 
ArcadeTechGW said:
The board doesn't hit 700 Deg F. It's a fraction of that.
Click to expand...
ReWrite said:
Do you run your games inside a kiln!?
Click to expand...
The soldering iron is about 650º+ Desoldering is at 750º approx. So to stand up to the tests of time I'd say the glue/epoxy *under a soldering pad holding it in place permanently* obviously needs to stand up to at least 700º to be safe. ??no?? Am I missing something here ?
 
Don't try to overthink the solution for a lifted track or pad in this situation.

The track/pad has lifted from extreme heat from the component lead dissipating through the copper and fr4 over time. If you "glue" back the pad like it was before it will after a while do the same thing again.

One work around, that you mentioned, which works ok, although not the only solution, is to add some heavier gauge wire (like a trimmed component lead) to the area where the pad is/was and over to the nearby copper for that track (after removing the solder resist in that area). Apple a generous flow of solder. This achieves 2 things. 1 it restores the connection for the broken pad/track. 2 it adds some heavier gauge copper (compared to the track) and the solder to be able to dissipate the heat from the component lead better.
I sometimes get a long enough wire and double it over (for the track part) and leave a small hole where it was doubled over for the component lead. Then if it does need to be worked on later you can still use a desoldering iron to remove the solder at the lead.
 
Your two pads doesn't look bad. Just glue it back down with some dollar store Krazy glue and then solder. You can also scratch off some of the solder mask exposing the trace and flow solder from the leg to the trace. If you're still not confident with that, you can go for overkill and bend the leg over to the newly exposed trace and solder everything together for maximum adhesion.
 
Infa Red said:
The soldering iron is about 650º+ Desoldering is at 750º approx. So to stand up to the tests of time I'd say the glue/epoxy *under a soldering pad holding it in place permanently* obviously needs to stand up to at least 700º to be safe. ??no?? Am I missing something here ?
Click to expand...
You are overthinking this.

Heat transfer is a complex process. Heat flows at the connection point, in this case where the tip contacts the board. When you heat the solder, it transfers heat QUICKLY to the thin copper pad, and more slowly to the PCB itself which has a large mass.

Or consider this: If you put the soldering iron on the board itself (away from any connections) how long does it take for the board to turn brown or black? That's called thermal lag - the time it takes heat to penetrate the entire board to the point where it can raise temperature enough to brown or blacken that spot on the board. It isn't a few seconds - its more like 15 to 30 seconds, depending on the board material and thickness.

Use the right solder and right touch, and it will be fine.

Don't linger on the pad, remember to heat the lead first (this has the biggest thermal mass other than the board so you need to heat it up so the solder will adhere to it), then slide the soldering iron tip down to the pad while maintaining contact with the lead and apply solder. Bam, you'll be done and the pad will stay down.
 
Ok makes sense ! Appreciate the advice and links guys. I will do as we said, maybe even just for practice and learning I will try a little of the overkill method too. Its a big area kind of perfect to learn this method on. Also for some reason, this seem fun to me. This is my first lifted pad situation. GOD I love this group of people here. Ya'll so knowledgable and helpful and also help in a way that I like with jokes and good ribbings thrown in ! haha,

You know, back to another subject, we never elaborated on what we think the cause was more likely ? The yoke wire breaking off (but was it even broke off while it was running ?) Or this lifted pad(s) on R96 ? (but in theory it was well soldered to the copper)...

Here is the question that helps narrow it down IMO - for the screen to collapse the way it did, which sides yoke wire would need to be disconnected ? The lower number side or the higher number side ?

I am having a feeling, R96's path was fine, it didn't "look" fine, but for electrical flow, it was fine. Therefore I'd put my money on it being the yoke wire. But could be wrong of course.
 
Infa Red said:
Ok makes sense ! Appreciate the advice and links guys. I will do as we said, maybe even just for practice and learning I will try a little of the overkill method too. Its a big area kind of perfect to learn this method on. Also for some reason, this seem fun to me. This is my first lifted pad situation. GOD I love this group of people here. Ya'll so knowledgable and helpful and also help in a way that I like with jokes and good ribbings thrown in ! haha,

You know, back to another subject, we never elaborated on what we think the cause was more likely ? The yoke wire breaking off (but was it even broke off while it was running ?) Or this lifted pad(s) on R96 ? (but in theory it was well soldered to the copper)...

Here is the question that helps narrow it down IMO - for the screen to collapse the way it did, which sides yoke wire would need to be disconnected ? The lower number side or the higher number side ?

I am having a feeling, R96's path was fine, it didn't "look" fine, but for electrical flow, it was fine. Therefore I'd put my money on it being the yoke wire. But could be wrong of course.
Click to expand...
The yoke wire probably was broken to the point it was getting hot - it has X # of strands, if you were down from that to one or two, it generates heat. This heat caused the pad to lift due to the excessive heat at that connection, so when you moved the wire, the pad popped.
 
DuffCon said:
You need to watch some of @zenomorp 's vids on trace/pad repair. He covers this subject in almost every video:

Click to expand...
Crazy, when he got to R96... pads were lifted too ! He doesn't bother gluing, just scrape a little of the adjacent mask off and blob solder.

It also lets me know, this is a common spot for this. Makes e feel better. Thanks for sharing this video.
 
Azure Oz2 said:
.... Check chassis solder joints on yoke connector, check wires to horizontal connection on yoke ....
Click to expand...
It was in the first suggestion. I suspect it was completely broken and hanging on from the insulation with the connection wire only touching the connector pin.
I think the broken pads came from working it. They are prone to failure over time and were going to be a problem anyway.
 
I went ahead a installed the K7000 kit in my Pit Boss, worked like a champ and looks great! My 18 year old daughter has been playing it for about a hour now LOL
 
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