Testing voltage on an IC: K7000

mc300baud

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ok, i've got this really cute 9" WG K7000 that has vertical collapse. i just did a cap kit on it, checked and reflowed any questionable solder joints, and nothing changed.

looking at the flowchart it states "Test for +24 VDC at IC3, pin 6." ok, i know i should connect my positive lead on my multimeter to pin 6, but what exactly do i connect my negative lead to?
 

to test a wall outlet for 120 A/C you put both red and black leads into both sides of the socket, not on the 3rd ground pin because you are measuring both "legs". set the multimeter at A/C 200

here is a quote from a member here who i've forgotton his name(please forgive me)
but i havent forgotten his words:

"AC is not DC, and as such where you put the leads is a little different. With DC and electronics, there's usually a common ground. With AC, there is no common "ground" so to speak - there's the two AC wires, so you need to test between those two.

Secondly- since AC is a lot more lethal than the 5 and 12v dc we usually play with, please be careful dealing with the fuses, I think the AC fuses are not protected and can kill if its plugged in and you touch the wrong thing.

Basically, look at the power brick and follow the cord as it comes in. Unplug it and dust off the wires with a cheapo paintbrush or shop vac if need be. It'll be very easy to follow once you see how they go. The cord is going to come in, prob go through 1-2 fuses to fuse the actual AC power, then split to feed the two transformers - one is an ISO that feeds the monitor, other other makes the lower voltages that feed the board. Those lower voltages in this case are still AC so you need the AC mode to read them.

Here's an easy test - if you put your meter on AC 200v, and read across each fuse (one lead on each end off the fuse) - a blown/bad/dirty fuse will show full voltage. A good fuse will show no voltage across it."
 
to test a wall outlet for 120 A/C you put both red and black leads into both sides of the socket, not on the 3rd ground pin because you are measuring both "legs". set the multimeter at A/C 200

here is a quote from a member here who i've forgotton his name(please forgive me)
but i havent forgotten his words:

"AC is not DC, and as such where you put the leads is a little different. With DC and electronics, there's usually a common ground. With AC, there is no common "ground" so to speak - there's the two AC wires, so you need to test between those two.

Secondly- since AC is a lot more lethal than the 5 and 12v dc we usually play with, please be careful dealing with the fuses, I think the AC fuses are not protected and can kill if its plugged in and you touch the wrong thing.

Basically, look at the power brick and follow the cord as it comes in. Unplug it and dust off the wires with a cheapo paintbrush or shop vac if need be. It'll be very easy to follow once you see how they go. The cord is going to come in, prob go through 1-2 fuses to fuse the actual AC power, then split to feed the two transformers - one is an ISO that feeds the monitor, other other makes the lower voltages that feed the board. Those lower voltages in this case are still AC so you need the AC mode to read them.

Here's an easy test - if you put your meter on AC 200v, and read across each fuse (one lead on each end off the fuse) - a blown/bad/dirty fuse will show full voltage. A good fuse will show no voltage across it."
He's measuring DC not AC though...
 
i know, hes asking questions though and i wanted to pass along more info to him.

is this all you have to offer him?
I didn't offer him anything. I actually had the same question and read your entire post which didn't provide any help or answer the question. He asked what ground point to use and you make a post about checking AC at the wall?

Now in reading all these posts again I can offer one suggestion. In regards to this comment.

mc300baud said:
so any ground point will do? that makes it easy.

No any ground point will not do. Make sure you are using a DC ground on the chassis and not using the wall outlet as a ground.
 
No any ground point will not do. Make sure you are using a DC ground on the chassis and not using the wall outlet as a ground.

Well, actually....

If the game is plugged in, and the monitor is plugged into the normal power connector, then the frame will usually have a ground strap on it connected to the field ground on the line filter (eventually) and on to the wall outlet, which is tied into the other outlet, so it might work that way.

But just use the side wall like I recommended earlier...
 
the side wall worked just fine, and i have 24v at pin 6 like i should.

after that i pulled the chassis again, traced everything and it looked just fine. i took closer look at the yoke and noticed that the fine copper wires that lead to the windings from the yellow wire are broken, which i would guess is why i have no vertical deflection.

unfortunately it's a 9" monitor and of course i don't have a spare yoke sitting around for it like i do 19" K7000's... and i'm not sure if the fine copper wires are repairable, even if i could verify which i need to fix (one is obvious, the other not so.)

i may post a picture of the damage, but i'll probably start a new thread for that as it's a new question.
 
the side wall worked just fine, and i have 24v at pin 6 like i should.

after that i pulled the chassis again, traced everything and it looked just fine. i took closer look at the yoke and noticed that the fine copper wires that lead to the windings from the yellow wire are broken, which i would guess is why i have no vertical deflection.

unfortunately it's a 9" monitor and of course i don't have a spare yoke sitting around for it like i do 19" K7000's... and i'm not sure if the fine copper wires are repairable, even if i could verify which i need to fix (one is obvious, the other not so.)

i may post a picture of the damage, but i'll probably start a new thread for that as it's a new question.
Sorry to hear about the broken wire. Since this thread is about monitor collapse though I had a question about the flowchart. Where it says
if 6v is mission on pin 6 of IC3 then R93 might be open. Substitute IC3, IC2. Replace C50.
Does "substitute" mean replace? Should they be replaced only if R93 isn't open?
 
Substitute DOES mean replace. What that means is start at checking R93, then the following parts MIGHT be bad. Unfortunately, the flowchart only mention major or common parts. Most of the time, the problem is something not mentioned on the flowchart....
 
mabye you could scrape the varnish form the end of the wire thats broken and resolder te wire there?


i wonder if the yokes the same one from a 13?....hmm...
 
it looks like one wire snapped off near the top, and the other may have lost a chunk... neither appears to be an easy resolder. any suggestions on scraping off the varnish without further breaking the wire?
 
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