K7000 Vertical Collapse - Stuck

fredster

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Ok,
I'm a remove and replace kinda guy, and I have a fair to good success rate, but I'm floundering on this one.

This monitor has been going out for a while, and finally the thing collapsed. I put in a new cap kit. so that means I put in a new C50. After that replaced the R91, a new IC2 and IC3. Still has Vertical collapse. Is there anything else in that circuit I can try?

I checked the tube with another chassis just to make sure it wasn't the yoke. It's okay. But I can't seem to get this one to work. It's just flat lining with moving colors.

Where can I check the 24V on this?
 
Trace everything from the vertical yoke pins back to the vertical IC. I've found broken traces that way that caused collapse...
 
cant remember if r101 is in the vert circuit or not but its notorious for frying the traces going to it or at least the solder pard at the resistor. SOmetimes you dont see it untill you unsolder it only to find out the trace underneath is BLACK.

DOnt forget to check the pots to make sure none are cracked. CHeck the yoke pins for bad solder too. Best of luck.
 
i had one that D13 had a cracked pad. and that was the issue.
soldered it back down to the trace and it worked.

i replaced a bunch of parts the ic and other things even did continuity checks all over the circuit. drove me nuts for a week.

Peace
Buffett
 
check R81 and R82, also do an ohms test on C49 to see if its around a couple ohms...if it is replace it.
 
I tried again. I went as far as to replace D13 and checked the traces. Still the same. (This appears to be the first time this has been serviced)

I did a continuity check on all of the pins and diodes I replaced from the legs to the next components.

When I replaced IC2 and IC3, I took them from a donor chassis. Using the donor parts may be what's wrong here. I checked them with a diode check (a randy Fromm trick) before I put them in and the old/new were different, but now I'm not sure. I'm going to order brand new in the box IC2 and IC3's from Bob Roberts.

One thing that I did notice, the R91 I put in from the donor changed values. It looked a little fried after a 30 second test and I pulled it back out when I saw a discoloration (it is hard to get to, it's under that flyback cover). The one I replaced did that too. It went from 1.3 (it's a 1.2 ohm stock) to like 300 ohms. I put another one in and tried it again after I did what modessitt suggested. I didn't check it this second time.

cbuschief, LOL C49, R81 & 82 are about the only other things in this circuit! When I get the new chips from Bob, I'll replace all that and if doesn't work after that it will have a new life as a Frizbee!

This thing was working, but it was going out, and I let it. The kids were playing it and it went into collapse. If I had capped it before it went out, I wouldn't have had this problem, *sigh*. Show's an ounce of prevention is worth a LB of cure.

I appreciate all of your help folks.
 
The K7000 had several different versions of IC3, and they don't really swap. Did you replace the original with one of the same part number?
 
Yes. It's the one that has the first two and last legs clipped. I have 4 of these chassis. All of them have the 538 on the board. (I got them in a box deal at an arcade auction, I've got about 3 of everything). The other two are different. Hell, all of them are different.

Some of them have larger flybacks, some of them have the little IC3, some of them have caps on top of the flyback, etc.

I thought I'd just cap the one I had (since I knew it came from that monitor), then put in the IC2 and IC3 from one of them. I tried the others, but they all are as bad as this one. One has a fuse burnt and busted, the other one won't come on, another had the same collapse, etc.

I took the IC out of one that looked the best but didn't come on. I checked the IC's with a diode check and they were different readings, that is, it had a couple of shorts in it that the other one didn't. So it has to be bad IC's. I am waiting on the new parts order from Bob Roberts and I'll put them it. It has to be that. I traced every single wire in that circuit. It all looks good.

It's stuff I didn't think of and I really appreciate all of the help from you guys!

I'll post back when I get them in. If I fail, I'll make somebody a helluva parts deal on a rebuild job LOL!
 
Sounds like you may have a K7000A mixed in with the K7000's (your reference to "larger flybacks"). Don't mix parts between them...
 
Did you test Q7? I didn't see that in the list of what's been done. Check the solder job and traces there as well. Also check C22 if the transistor is OK or not the problem.
 
No, I did not. I have a spare Q7,(they are like a quarter) and I'll just replace that too.

I should be more clear, the chassis is actually what I believe to be a 25K7191. Not an actual K7000. But they are nearly identical.

I didn't order the right IC3. There are two of them and I got the wrong one for the replacement. This Chassis has a LA7831, and I got a UPC13978. So I am going to wait for the right part. (I did put the correct one in from the spare chassis I had).

Once I get all the right parts that I'm sure are good, I'll jump into it again and report back.

Thank you all for all your help. You guys are great.

I learn more from screwing something up than when I luck out and fix it sometimes!
 
Others have already mentioned checking the yoke header pins on the chassis, but check the yoke wiring itself too. Measure the Ohms on the yoke. Inspect the vertical pairs of wiring for a possible break "inside" the connector that plugs into the main chassis.

I only mention this because I've had one that did this and you will chase it around for days and not think to look there, it will drive you crazy. (and turned out to be so simple) Since then I check all the dumb stuff like that first before digging into the chassis itself.

Also, if you hadn't done so already...check that you actually have 24vDC between pin 1 & 6 on the IC3. (1 is ground, 6 is positive) This will at least give you a general direction to look in. Or at least eliminate another possibility.
Like buffett's example of D13....he lost power to the IC because of that particular diode.
 
Also, if you hadn't done so already...check that you actually have 24vDC between pin 1 & 6 on the IC3. (1 is ground, 6 is positive) This will at least give you a general direction to look in. Or at least eliminate another possibility.
Like buffett's example of D13....he lost power to the IC because of that particular diode.

i had tested all the parts in that circuit they all tested good and could not find out why i did not have power to the ic. then i found D13's pad was loose when i physically wiggled it.

something simple that i had completely over looked and had took for granted. and it had me pulling my hair out.

another example i have a G07 and it had vertical colaps with known working chassis. turns out that one of the small copper wires on the yoke was broken. so be sure to check every thing.

Peace
Buffett
 
I found D13 shorted, and R91 way out of value, like way. I did a diode check of the old IC3 and found Pin 6 dead short. The one I have in the chassis checks with another board exactly now. I pulled the diode and resistor off my "donor board". Q9 is good.

I am going to replace C40 just for the hell of it, even though it's new because I ran it like that for a few seconds. (I am going to have to buy a capacitor meter). I now have to go through all these other resistors to see if any of them are open along Pin 6.

Maybe the old C40 (2220uF 35V) blew, and took out the P/S to the IC3.

But I'm out of time for tonight.
 
For future reference there is a sticky for K7000's which pretty much tells you what to check for for specific symptoms/issues.

Sticky
 
For future reference there is a sticky for K7000's which pretty much tells you what to check for for specific symptoms/issues.

Sticky

I read through the sticky to get where I was at. This problem wasn't covered in the threads there. I did all of the vertical deflection stuff in the thread, but Diode 13 wasn't in it. (specifically - Vertical collapse even after replacing ic2 and ic3)

Maybe one of you could add this problem/resolution to the sticky.

After replacing IC2 and IC3, still no vertical deflection. After reflowing everything connected to the vertical yoke wires, found that D13 was shorted, and R91 (one close to the flyback) was burned up and out of range. It's supposed to be a 1.2 Ohm. It was reading in about 300K ohm and it actually looked toasted. Once I replaced resistor and diode, the board had vertical deflection again!

R91 was in Fromm's troubleshooting guide, but the shorted D13 was not. Kuddos to Buffett for suggesting it!!!!

Here's a pic attached. Unfortunately, the red is flaky, and finally went out. But I'll pull it again and replace Q201 and check all that. Missing colors, I can fix!!

Thanks again, you guys are great!!!
 

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