K7000 sync blew out monitor

[churd]

Hi All,

I recently upgraded the computer powering my cabinet, and while setting up the video card/Soft-15Khz the wrong scanrate got sent to the monitor, blowing out the picture.

The monitor is a WG K7000 series (19k7602, specifically).  Based on what I had read on the forums, I replaced the HOT on the board (and a few capacitors that were suspect).  I now can hear the monitor powering on (slight whistling), but there is still no picture or glow showing on the screen.

Unfortunately, I am very new to monitor repair, so most of the K7000 service manual is greek to me.  Does anyone who's worked with this monitor before have any suggestions as to where to check next?  Also, if there are any resources online, etc. that might be of help, please let me know.

Thanks!

[grantspain]

what transistor did you change?

[Kevin Mullins]

Check Q7 - 2N3904
Check IC2 - LA7823

[churd]

Thanks for the replies - the transistor I replaced was Q11 - 2SD1398.

I'm unfortunately traveling and can't test, but for when I can, what is the best way to test the IC2 chip?  Is that a Voltage check with the monitor powered on (there are readings in the service manual, so I'm assuming that's what to do).

[churd]

Hello all,

After trying a few things out, I still can't get this monitor to display.  I've done the following:

Replace Q7
Replace IC4
Replace IC2

I am still not getting any picture on the screen, although I do hear a whine when I power on the monitor.  Based on my reading, it seems like I am getting no high voltage, but I am at a loss as to how to test or what to try next.  Any suggestions or advice for how to continue testing?

[grantspain]

go back and check what you have done already and double check q11

[churd]

Ok, following the flowchart here...

R301 and Q11 are both measuring around 155-156 volts, which I read means Horizontal Deflection failure.  I replaced IC2 again just to make sure, but still nothing (with or without D10 in place).

I checked all the other pieces that could be the cause (Q10, R89, R101) except for T2.  Is there a way to test this or is it likely that this is the cause of the problem?

Also, the IC2 chip I replaced was an LA7823, but the original piece is on backorder, so I used an NTE7123 (apparently the replacement for this chip) - is this acceptable, or potentially the reason it's still not working?

Thanks for the replies!

[grantspain]

the nte ic does check out as an exact match according to the datasheets

according to the repair guide you should look at c36 and d10,12

[churd]

Been a while since I worked on this, but I finally got a C36 - replaced that, still no good.  After that I did a full cap kit, but we're still in the same place.

D10 and D12 test out ok, and even with D10 lifted there's no high voltage to the tube.

Is it possible T2 needs to be replaced?  I saw on one of the flowcharts I was using that it could be a culprit.  I'm not sure where I can order that piece from, does anyone have any suggestions?

[Ken Layton]

The B+ voltage regulator IC mounted to the frame by the big white ceramic resistor may be bad. It will have an STRxxxx or STRxxxxx number on it.

[cadillacman]

+1 if a hot goes  on these k7000s about 1.2 the timne the voltage regulator goes too...

try one and see whatcha get!

also have you checked for bad solder connections around r98-r101???

[churd]

Well, it took months to fix, but only 5 minutes of troubleshooting to make me feel like an idiot!  After replacing the Voltage Regulator again to no avail, I ended up checking the solder connections on the board as suggested.  I then noticed I had a cold solder joint on the HOT (the first thing I replaced, of course!).  After resoldering that one point, everything worked perfectly.

I guess on the bright side, after doing the full cap kit and replacing the IC chips the picture quality is better than it's ever been, so that's a plus 

Thanks guys for all your help trying to figure this one out.

[cadillacman]

K7000s are fun, aren't they

Sent from my Z777 using Tapatalk

[ZPaul2Fresh8]

My K7000 on my MK2 had Reds fading out on the right side. Found cold solder joint at the PCB to Chassis board connector pin #1 (Red). Works great after adding a cap kit and a fresh filter.