Author Topic: WG K7000 1 problem to the next (Read 8897 times)

Silverball84 · « **on:** June 17, 2013, 08:09:01 am »

I have a 19" wells k7000 which I thought was going to be an easy fix. It has vertical collapse after a few minutes. Upon moving the chassis from location to test tube I noticed the thermistor at r105 had come unsoldered. So I resoldered it and installed the chassis on my tube for testing. No power up... Check voltage going into isolation transformer 125vac... Voltage coming out is 5.6vac??? I ran out of time to keep going at this point so any suggestions before i dig back in would be great.

mgb · « **Reply #1 on:** June 17, 2013, 09:45:11 am »

Have you first tried going through and just re-soldering all points.

Silverball84 · « **Reply #2 on:** June 17, 2013, 11:54:19 am »

It appears that someone else has done that already, but I do need to verify clean solder joints. It did work for the first few minutes when I removed it from location. I get absolutely nothing. Not even a slight noise when I power it up. Isolation transformer is fused but its not blowing. Just not sure where 115 volts are going?

grantspain · « **Reply #3 on:** June 17, 2013, 04:08:45 pm »

check the iso with chassis power disconnected
you may have a shorted diode in the ac primary-shorted diodes do not always cause a fuse to blow btw
watch out on k7000 that the fuse is also correctly rated and is a anti surge or time delay type

buffett · « **Reply #4 on:** June 18, 2013, 02:37:16 am »

if the fuse is good check R103 and see if it is open.

remove it to check.

if you need it fixed and you are in the US or canada i can do it for you.

Peace
Buffett

Silverball84 · « **Reply #5 on:** June 18, 2013, 07:56:32 am »

I went and spent about 10 minutes wire brushing the last repair persons rosin flux off the bottom of the board. Then inspected for cold solder joints. Found nothing...checked r103...good. I pecked on the shutdown pot to try to get it to turn, but was unsuccessful. However I hooked it up and it powered up. Definately gonna replace that pot. So I think that takes care of problem 1. It has the dreaded white knob flyback, and it sounds to be arcing internally. I think its gonna get a flyback, and a 2k shutdown pot before further testing.

mgb · « **Reply #6 on:** June 18, 2013, 11:43:19 am »

I always find it good practice to resolder points.
Maybe you've got other issues here but for the relatively short time it takes to resolder, I'd do it anyways.
If it appears someone else has already done it, then they may have done a crap job otherwise you wouldn't so easily be able to tell they were in there.

buffett · « **Reply #7 on:** June 18, 2013, 02:16:40 pm »

i would not replace the shutdown pot i have never seen one that was bad.

plus there is no way to adjust it it is factory set.

if it is coning on now you have a or more cold solder joint/s somewhere.

put a cap kit and flyback on it before it kills other parts when it goes.

if you need parts i have everything you need.

Peace
Buffett

Silverball84 · « **Reply #8 on:** June 18, 2013, 02:23:26 pm »

Originally this monitor had a vertical collapse issue. I have another 7000 chassis to swap some parts from. I will resolder points as I'm swapping.

buffett · « **Reply #9 on:** June 18, 2013, 02:27:34 pm »

if the monitor works without swapping any parts not in the vertical section then do not replace them.

i would reflow the chassis before you swap parts and possibly waste time.

it could just be cold solder joints that are causing the issue.

Peace
Buffett

Silverball84 · « **Reply #10 on:** June 18, 2013, 05:36:59 pm »

That is a good point however, the flyback is a piece of crap and my spare chassis has a good one. I was just gonna swap that during the resolder.

buffett · « **Reply #11 on:** June 18, 2013, 06:15:28 pm »

sounds good.

do you want the other chassis fixed as well.

i have all the parts to repair theses chassis.

Peace
Buffett

Silverball84 · « **Reply #12 on:** June 20, 2013, 11:03:56 am »

I was able to do some more work last night. Re-flowed solder, and it does consistently power up. Still have the original vertical collapse problem. Will keep progress updated. Thanks for the help.

buffett · « **Reply #13 on:** June 20, 2013, 11:19:27 am »

check D13 to see if it is open or you have cracked traces or pads.

you may need to sub out the vertical IC.

Peace
Buffett

buffett · « **Reply #14 on:** June 20, 2013, 05:46:52 pm »

also check that the vertical pot is not broke.

if it is you will never have any vertical deflection.

Peace
Buffett

Silverball84 · « **Reply #15 on:** June 21, 2013, 09:48:53 pm »

Vertical pot is ok...D13 and D14 check good. Swapped IC1, 2, and 3...Swapped Q9. C24, C25, and C50 are good and R65, R66 test good. What else is in the vertical circuit is there?

buffett · « **Reply #16 on:** June 21, 2013, 11:03:38 pm »

possible broken trace or pad.

check all the parts behind the vertical heat sink also.

Peace
Buffett

Silverball84 · « **Reply #17 on:** June 25, 2013, 01:08:20 am »

Can't seem to find it. It makes a weird arcing/chattering noise once the vertical collapses. When I tap the plate the flyback is mounted to the monitor dies. Unplug it and reapply power and it comes up. I'm still thinking maybe this flyback is not so good. Is there any possible way the flyback could cause no vertical. At first power up after sitting for a day or two it will have a picture for a few seconds, then it gradually collapses within a few seconds. I have soldered every common place on the board. Never had a vertical problem this troublesome.

buffett · « **Reply #18 on:** June 25, 2013, 01:13:55 am »

did you install a brand new flyback or another used one.

if you are tapping on the heatsink and the monitor goes out you have a broken trace or pad somewhere.

sometimes they hide so well you will not find them unless you desolder all the solder from a pad to find it.

Peace
Buffett

Silverball84 · « **Reply #19 on:** June 25, 2013, 07:41:46 am »

I installed a used one, but it doesn't power up with it so I know its bad. I am going to buzz out everything on that side of the chassis and try to find a break. If I can't find my new flyback i'll have to buy one. Thanks for all the help your throwing my way.

buffett · « **Reply #20 on:** June 25, 2013, 12:23:02 pm »

no prob.

it is always best to use new parts when working on a chassis especially the high failure parts of the past.

replace with new and start fresh on a repair so you do not struggle to find that the second old part is just as bad s the first.

sometimes you will not find it with a meter because when you press down on the pad or trace you make the connection unintentionally.

on most parts the wiggle test is the best way to find a broken solder pad.

Peace
Buffett

Silverball84 · « **Reply #21 on:** October 01, 2013, 09:13:43 pm »

OK...I know its been a few months since I've posted anything on this. I figured I would give an update. I ordered a full flyback repair kit for this chassis from Bob Roberts. Replaced flyback, hot, and caps. Found a few cold solder joints and removed all excess flux and solder splashes from the board. Now the monitor blows the fuse. Tried a different voltage regulator, checked diodes, checked degaussing circuit. Im Stumped again. Help

buffett · « **Reply #22 on:** October 01, 2013, 09:20:15 pm »

check C36, 37, 38 and the H.O.T for a short.

if any of them test shorted pull them and check them out of circuit.

if you want to send it in for repair let me know.

Peace
Buffett

Silverball84 · « **Reply #23 on:** October 01, 2013, 10:38:19 pm »

I will check these all. I'm wondering if the new HOT is good. I replaced it, but only because it came in the kit. I did put fresh compound on with the mica insulator. Would any of these cause a partially collapsed picture? That was my original issue. This thing has been a chore from the beginning.

buffett · « **Reply #24 on:** October 01, 2013, 10:40:05 pm »

what compound type/brand did you use.

Peace
Buffett

buffett · « **Reply #25 on:** October 01, 2013, 10:40:39 pm »

what thermal compound type/brand did you use.

Peace
Buffett

Silverball84 · « **Reply #26 on:** October 01, 2013, 11:03:37 pm »

I'm not sure what brand, but its the white thermal paste that gets all over everything. Not the silver kind for CPU heatsinks.

buffett · « **Reply #27 on:** October 01, 2013, 11:06:50 pm »

as long as it is not that silver crap.

plain old non conductive thermal paste is what you want.

sounds like you have the rite stuff.

Peace
Buffett

Silverball84 · « **Reply #28 on:** October 03, 2013, 08:39:44 pm »

OK checked out some more components tonight. C36 is the 4 legged original in which one side is 6.2 pF and the other fluctuates which leads me to believe it fails under a load. C37 and 38 are not shorted. Is it better to check the hot out of circuit. It shows low values on my meter but not a dead short.

buffett · « **Reply #29 on:** October 04, 2013, 02:13:00 am »

C36 should measure the same on any lead on each side.
pull it and measure it again.

post your readings for the H.O.T.

anything that tests funny should be pulled and tested again.

Peace
Buffett

Silverball84 · « **Reply #30 on:** October 04, 2013, 07:01:07 am »

I will pull the hot and check it out of circuit. I still have the old one and a spare in another chassis.

Silverball84 · « **Reply #31 on:** October 06, 2013, 06:23:57 pm »

OK pulled my new hot and it checks as follows...b to c .04 b to e .03... this one is no good obvious my to others have b to c at .456, however b to e is still .03 so I'm thinking they are also done for. I'm thinking new safety cap and hot. Could my new flyback be shot now too?

buffett · « **Reply #32 on:** October 07, 2013, 12:37:29 am »

pull C36, 37, 38, (69 if it has one) and measure them out of circuit.

they will all short a H.O.T.

some other things will as well but theses are the most common culprits.

i would not suspect the new fly ATM.

Peace
Buffett

Silverball84 · « **Reply #33 on:** October 07, 2013, 06:32:37 am »

C69 isn't screened on this one. Just 4 holes for c36. I did pull c36 out and checked it on cap function. That's where I got a good reading on one side and intermittent on the other. Of course the ends are bridged and they both test that way. I will pull 37 and 38 to test as well. Thanks

Silverball84 · « **Reply #34 on:** October 09, 2013, 10:03:50 pm »

OK disregard the last post all three caps test good. I downloaded a schematic so I can trace back from the HOT.

Silverball84 · « **Reply #35 on:** December 08, 2013, 11:13:44 am »

I know I let this post get buried, but I have been tied up with other things. I am going to order a new HOT, and see what happens. I'm thinking I had a bad new HOT in my fly kit that I installed.

buffett · « **Reply #36 on:** December 09, 2013, 12:07:24 am »

check it before you replace it.

also you did replace the insulator behind the H.O.T.

Peace
Buffett

Silverball84 · « **Reply #37 on:** December 09, 2013, 05:26:37 pm »

What should the base to collector residing be? It has the insulator however not new. I'm testing the HOT on diode function.

buffett · « **Reply #38 on:** December 09, 2013, 05:30:19 pm »

.400ish to .700ish somewhere in between there.

Peace
Buffett

Silverball84 · « **Reply #39 on:** December 09, 2013, 06:32:24 pm »

All 3 I have read .03


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