K7000 - Swapped Yoke Wires

Peale

Active member
Joined
Sep 1, 2003
Messages
3,469
Reaction score
15
Location
Brattleboro, Vermont
My 25K7000 test rig is a tube I salvaged from a TV (and yoke) along with the original yoke connector from the original tube.

Stupidly, I don't have the yoke connector hooked up to the yoke wires very securely. And, hooking up color to color (red to red, blue to blue, etc) makes the picture reversed. It's never been that big of a deal, I always make sure nothing is touching before firing up a chassis.

When I went to hook up the tube to a chassis, I found that two of the wires had come disconnected from the connector. Without thinking about it, I just swapped the wires, thinking that it would be nice to see a proper picture.

Yeah...dumb. The equivalent of swapping horizontal and vertical. Now, the chassis has a B+ of ~12VDC. A brief moment of high voltage when it's first fired up, then that's it.

I'm assuming that the voltage regulator is toast, to start. What else?
 
My 25K7000 test rig is a tube I salvaged from a TV (and yoke) along with the original yoke connector from the original tube.

Stupidly, I don't have the yoke connector hooked up to the yoke wires very securely. And, hooking up color to color (red to red, blue to blue, etc) makes the picture reversed. It's never been that big of a deal, I always make sure nothing is touching before firing up a chassis.

When I went to hook up the tube to a chassis, I found that two of the wires had come disconnected from the connector. Without thinking about it, I just swapped the wires, thinking that it would be nice to see a proper picture.

Yeah...dumb. The equivalent of swapping horizontal and vertical. Now, the chassis has a B+ of ~12VDC. A brief moment of high voltage when it's first fired up, then that's it.

I'm assuming that the voltage regulator is toast, to start. What else?

The yoke fried? Better measure it...
 
Heh, I've also done the exact same thing. I was rigging up a donor tv tube (left it in its plastic case) and half assed the yoke wires.. While showing a buddy how cool I was on making a tv work with an arcade game, I crossed a few yoke wires. Bit of smoke, spark or two.. But I unplugged it within a few seconds.

Rewired it up and it worked fine. Guess I didn't smoke the yoke! I'd assume you would have damaged the yoke first, then of left on long enough other things would have burned up. How long was it on?

On another note.. Ever have a yoke catch fire? I did! Smoke started coming out of my centipede cab a while back. Turned it off, opened it up and noticed the yoke was crusty. Weird, as this game has been perfect for years and I've never messed with it. No dust, or other crap in it. It was a k7000, installed another yoke its happy again.
 
Swapped out the STR30130 and now I have a B+ of 145VDC. I'm not sure if this VR is good or not, though; I did a couple repairs on K7000 back when I was moving my shop, and I may have put parts meant for the trash in my parts bin. I wish there was a way to test it.
 
Swapped out the STR30130 and now I have a B+ of 145VDC. I'm not sure if this VR is good or not, though; I did a couple repairs on K7000 back when I was moving my shop, and I may have put parts meant for the trash in my parts bin. I wish there was a way to test it.

K7191... FU! lol. I have one I was working on a couple weeks ago, I dropped a new VR in it and powered it up not knowing the R301 was cracked in half last year (doh!) so there's a likelihood that I may have messed up my new IC4 that way. I too don't know how to test them, so if someone has a procedure for which legs to meter to what, I'm highly interested. I believe I have another IC4 that I replaced for the hell of it that was still good that I could try dropping in if that one is bad.

ThunderBunny had one that was giving him all kinds of shit. I found new items to test from his thread, just haven't gotten around to it trying to get our outdoor operations running and me being a dumbass and injuring myself on the job.
 
When testing the IC4, i just check for shorts. I start with the black lead on the end leg, then put the red lead on each of the others. then move the black lead one over and check the others with the red, and continue until all combinations have been checked. if I have no shorts, I assume it's okay and move on. I don't often find VR's that aren't shorted to be bad, so I don't change it unless I've exhausted just about everything else...
 
When testing the IC4, i just check for shorts. I start with the black lead on the end leg, then put the red lead on each of the others. then move the black lead one over and check the others with the red, and continue until all combinations have been checked. if I have no shorts, I assume it's okay and move on. I don't often find VR's that aren't shorted to be bad, so I don't change it unless I've exhausted just about everything else...

ah ok. I was certain that was the way to test it. just for further clarification, you DON'T want it to come up with like a .001 in a continuity check that = short right?

depending on if I get around to it or not, cause I'm swamped at work with trying to get everything open again outside for spring.
 
ah ok. I was certain that was the way to test it. just for further clarification, you DON'T want it to come up with like a .001 in a continuity check that = short right?
Sure is. I personally prefer to use the resistance setting as it'll also tell you if something's open circuit.
 
Still poking at this. It's going into shutdown. Pot appears okay. R104 is getting /really/ hot for some reason, before it shuts down. I brushed my wrist against it, and was surprised how hot it was.

Swapped out another VR - just in case the one above was faulty. No. Same result.

With D10 pulled it fires up, but no picture, with a B+ of 130VDC. If it starts cold, it'll run, but if you turn it off, then back on a moment later, it's in shutdown. B+ of 145VDC.

This is really aggravating.
 
for giggles, replace those two caps next to the shutdown pot.

Good call! Although I didn't replace them, that's the first thing at which I looked. I can't remember which cap it was, but one of the legs WAS NOT EVEN IN THE HOLE. How it operated before this, I can not say. How the cap had a leg out of the hole is very, very odd. It now fires up each time I power it up, with a spot-on B+, but still with no picture. The heater is also not coming on. Metering the voltage on the neckboard for B+ yields 0VDC (or very close to it).

Also: it was R105, not R104, that was getting very hot.
 
check R213 on the neck board to see if its open or two far out of tolerance.

that is in line with the heater and the trace from the fly.

i repaired a 7400 that the resister was to far out of value and it was not turning on the heaters after i replaced it i had raster and neck glow.


Peace
Buffett
 
IIRC that was the first thing I checked (along with the rest of the heater circuit) but I'll check again, to be sure.
 
from what i can tell it comes off the winding of the fly threw the connector to the neck board and into the heater so it cant be much in that circuit that i can see.

ohm the wire in the connector to the neck to see if its open. maybe it got so hot and fried it. or a cold/broken solder joint/trace is causing the problem.

Peace
Buffett
 
The heater circuit is remarkably simple; I'll check it again, later. But I'm fairly sure it's okay. I'll report any findings.
 
Here's something that I don't understand; how a piece of equipment can be running with one particular part for (likely) years, then it suddenly stops working, yet the part itself is still okay.

I checked R213, and it is a not .68 Ohm resistor, it's a 2 Ohm resistor. Another neckboard also has a 2 Ohm resistor. I haven't checked my others yet. But, my question is...

.68 is pretty much a dead short; on my meter, touching the leads together yields a reading of 1 ohm-ish. What is the risk of just circumventing the resistor with a piece of wire? I'm sure that there's a reason, but with that kind of resistance, it seems that the risks are slim.
 
what is the voltage on the input side of the resister.

we know that the heater runs on 6.3 volts.

so the resister must be cutting it down to that voltage,
so if it is to high then you will be burning up your heater faster than normal.

i would not jumper it yet till you know what voltage is present.

Peace
Buffett
 
Oh, son of a...two things.

1) somehow, the focus wire had broken off. I'd never even noticed. Why would I? No picture, no problem to track.

2) The solution to the issue - I'd removed the ground wire from the neckboard. A previous tech had done a really piss-poor job of repairing it (sloppy, with solder blobs everywhere) and I'd intended on repairing it properly. But I had to walk away for a few weeks, and forgot about the wire when I got back to it. Reconnected it, and it's back to where I started. Which is missing red, but I can live with that!
 
Back
Top Bottom