Need help with a WG K7193 chassis that won't fire up.

action76

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Need help with a WG K7193 chassis that won't fire up.

Ok long story short, I was converting a medium res tube to a standard. I got the 7193 chassis and a standard res yoke to swap. In my anxiousness I hook up the chassis and forgot to swap the yoke. It heard it come on briefly and then off. The fuse was blown. I realized what I did and then swapped the yoke. Now the first time you plug it in after it has been off a while, you can hear the tube energize and then go off. If you unplug it and back in it does nothing unless it has been unplugged for quite a while. The R101 seems to be getting pretty hot and one end of the LA7823 IC gets warm also. Could this other yoke caused other damage to the chassis? If so am I looking in the right place with the resistor and IC?

Thanks.
 
you need to measure every resister in the horizontal circuit and every resister in the power supply.

i have the IC but not the resister.

you have probably damaged several things.

when you did the swap did you also add in a iso transformer if not then you may have smoked even more parts.

check all your diodes 19-24 and your VR for shorts.

if it has not been capped i would do that as well the caps are old and you could have damaged several of them also replace the fly wile your are there.

Peace
Buffett
 
Thanks for the reply

--you need to measure every resister in the horizontal circuit and every resister in the power supply.

I have already checked the res. and they all check OK

when you did the swap did you also add in a iso transformer if not then you may have smoked even more parts.

--check all your diodes 19-24 and your VR for shorts.

All the diodes are OK.
How do you check the VR for shorts? I tested The input and output voltage of the VR and both was approx. 160v. I think it should be 130v output, but is this only when the tube is coming on and 160v if it is not on? If so the 160v readings are right since the tube is not firing up.
 
pull one leg of D12 and see if the monitor fires up.

if it does then your VR is most likely bad.

when my video camera comes in i will be making tech videos on how to test all theses things so there is no confusion.

also did you re-flow the chassis especially around R101 and R89.

Peace
Buffett
 
Update: I desoldered the leg of D12 and the tube did fire up. I already have a VR STR30130 and HOT on order. I also noticed in my checking that pin 16 on IC2 seems to be an internal VR. That leg was getting 12v when I checked it and is supposed to get 16v I think. Does that mean the IC is bad or when the main VR is replaced that regulate to 16v.

Thanks for all your help!
 
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great it fires up:)

not positive on that for the IC.

but seems your VR is bad.

replace the VR solder D12 back in and check everything again.

Peace
Buffett
 
Got the VR in today and put it in and soldered D12 back in, and it fired right up. I have not hooked it back up to a board yet, but it had a good raster on the tube. I think all is good now. Thanks again for your help Buffett.
 
I've got another question. The monitor worked fine when I hooked it up. I adjusted all the settings: flyback focus and intensity, v-hold, v-size, black level, etc. It looked good except it was washed out and the contrast pot did not have any effect. I noticed that the ceramic was cracked. So I replaced the pot the next evening and turned it on and got what you see in the picture. I don't think this had anything to do with the pot replacement. Could a cap have gone bad overnight and caused this. What do you think it might be?

Thanks
 

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i am guessing it was the contrast pot you changed.

that looks to be a partial IC3 failure to me.
in order to find out if it is the culprit you will have to sub it out.

you can also check the wires on the grey E ribbon cable.
the ends get bent over and touch the other pad and can make for some funky video issues.


Peace
Buffett
 
Ok, I replaced IC3 and no change. I checked what I think you are talking about the E ribbon cable. If I am checking the right thing it looked ok. I've checked several resistors and diodes that were suggested in the sticky at the top of the forum and all seemed ok. Do you have any more ideas?
 
may sound silly, but is your chassis one that has stationary adjustment pots or is it a remote board? if you mentioned this already I apologize, I read the whole thread and didn't catch anything lol
 
It has a remote board with six pots. It has one pot on the main board, I believe it is H-hold. The one I replaced was contrast on the remote board.
 
are any of the other pots broken by chance? I headbutted one of those remote boards on accident sticking my head in a Suzuka 8 Hours cab once and wound up doing the same thing you did almost :D
 
All the others seem to be working fine. It is kinda strange because it was working fine one night. I was tinkering with it to get the settings right and discovered the cracked pot. The next evening I replaced the pot and when I turned it on, it was like that. I did unplug the remote board from its harness to work on it at the workbench and plugged it back up before testing it. Also I unplugged it to see what would happen after the screen collapsed, thinking the pot may have caused it, but other than the screen going bright white, the size of it was the same.
 
you will need to sub out/replace IC3 to see if it fixes the problem.

that is one of the most common failure points for vertical collapse in a K7000.
the next is broken pots and then cracked solder joints and broken traces.

Peace
Buffett
 
I did replace IC3 but there was absolutely no change. The LA7831 chip I used was off another parts chassis I had. Is it possible that it was also bad in exactly the same way that it produced the same result?
 
it could have been but who knows.

there are several different vertical IC's that wells used.

it was the same part # correct.

also check all the parts behind the heat sync as well. i have seen some of those parts fail.

Peace
Buffett
 
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LA7831 was what was in there, but it looked liked it had been replaced before. So I am not sure that was what was in it originally.
 
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