Ressurected 3 25" K7000 chassis today!!!

acblunden2

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I have been a total n00b until today. I have had like 10+ K7000 monitors waiting to be fixed for the past 1.5 years. First time I did a K7000 cap kit, I had a working chassis die on me. So I stayed away from the effort. "A ha" moment has been able to do a proper B+ reading. Once I was able to do that, Fromm's flowchart made all the sense in the world.

Chassis 1: Blowing fuse. HOT = shorted. D19-D22, good in circuit. Replaced HOT with proper thermal grease and mica insulator and she fired back up.

Chassis 2: Arching flyback. Replaced to find a big white blurry mess. Remote board and flyback adjustments did nothing. On a hunch, swapped remote boards and nice got picture. Bad remote board remained bad even after a solder reflow. New pots are on order to fix that remote board which I will save that repair for a later day.

Chassis 3: Same issue as Chassis 1. But upon firing her up, red was missing. Swapped Q201 and Q202 on the neckboard. The missing color followed the swap. Salvaged a transistor from what I have now designated as a parts board. Red came back. New transistors are on order.

Waiting for more parts for the other chassis but am happy and saving a ton of dough. Thanks for all you guys sharing your knowledge!
 
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Great work! Getting one going is always awesome but 3 is just badass.
 
Yeah, it is pretty rewarding. Especially since I have so many monitors to fix (see list below) and I am no tech either. At my day job, I sit in front of a laptop for hours on end. Put the time into learning the craft. That moment when I see the TPG's blue/black checkered image fade into view is pretty damn exciting. What really got me moving is that I picked up one of these media carts for $10 off Craigslist:

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Helps a ton with doing calibrations and getting readings. I wheel it in front of a mirror I have mounted in my garage to make the troubleshooting easier. Wheel it to my solder station as needed. Wheel it to my cabs to test the ones that have suspect wiring. Randy Fromm's flowchart has been a God send. Also, his lecture on Youtube is a revelation as well. Of course, the silly questions I ask here.

My list of monitors that still need work:
  • 8 more WG K7000's to fix
  • a 19" K7000 that is blowing the AC line-in
  • a dead 19" K7000A from the DAG wire coming apart at the connector that I installed
  • a 25" K7000A that I want to fix because I'm curious as to how much better the image is compared to a WG K7000, if I can source a flyback. Might pull that off the 19" K7000A
  • 3 K7400's
  • a dead G07
  • a Nanao MS8-29 with a tilted image
  • a dead tri-sync 29" Wells Gardner
  • a Neotec NT-33c that sometimes shows a double line
  • a QNIC CGM-2500
  • 3 or 4 Kortek/Sharper image monitors that I might just give away
Maybe I'll keep a log of all of them here as I go along. Someday, I might have a really nice man cave :)
 

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Nice work! I finally sucked it up and started doing y own repairs in the last year as well. It's a great feeling to bring one back. Best of luck on the rest, I have about a dozen here that I am slowly making my way through.
 
This is inspiration. I've been in the hobby 20yrs, but have NEVER had a dedicated spot for working on/testing monitors. I going to push to get a spot set up on the workbench this week. I need to better document/organize my monitor junk and repair/test some, and attempt more tube swaps.
 
Thanks for the kind words guys. I think I will start individual logs for each of the monitor types as I go along. Right now, I am seeing every issue under the sun with my K7000's =P. Should help n00bs like I still am out.
 
thanks for posting the symptoms and fixes.

I will have to be down this road later this month. With a few k7000 and some g07... Not lookinf forward to the maka tri sync... Im like 3rd owner of the bastard child....

But i mean... $20. Worth a shot, and came with a capkit from Kellogg.
 
I do have purity issues with that monitor too. Otherwise, it is beautiful.

Hopefully it's just out of convergence and rotated, i.e. purely mechanical. But even fixing that can be a complete b**ch. Great job on the first repairs tho!
 
I've fixed more K7000's since =). I have yet to find one in HV shutdown though. I must be sick, but can't wait till I run into one.

Back to that first ever K7000 chassis that I cap kitted and took from working to dead, I resurrected that one too. My error was that the cap map I referenced had polarity incorrectly listed. Spotted that after now being so familiar with the chassis. Replaced that cap and am back up and running.
 
that's one cool mobile setup.. what kind of cart is that and how much weight can it support.. tubes are heavy lol

I looked up media cart on Craiglist and searched for a while till I found one that works for me. It is designed to hold a TV and VCR and stuff like we had in school back in the days. So it serves this purpose just fine.
 
Whoohooo! One more K7000 chassis knocked out! This one had just about everything under the sun going on with it.

Initial Symptoms:
  • Dead w/good fuse
  • B+ Reading: 0VDC unregulated, 0VDC regulated
Replaced R103, still dead. Fired her up and could hear the crackling of of the flyback arching. Swapped out the flyback but it was still dead. But now have a B+ reading of 160VDC on both the B+ regulated and unregulated side. Replaced C57. Still dead. Checked for cold solder joints. Found R90 initially looked good, but had a lifted trace. Patched that with an axial lead and whollah!! Got the sizzling sound of electrons filling the tube. Image looked awful with discoloration, wavy vertical edges and horizontal lines across the top of the image. Decided to cap the rest of the chassis. As I was removing the old caps, first time I have ever experienced this, but the axial leads were falling out of the caps! Once all the caps were replaced, she looked good but the horizontal lines remained across the top of the image. Decided to swap tubes, and those lines went away and I have this nice looking image:
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Seems the width is out of whack (too narrow) so I need to get some width caps. Image is glorious however. Haven't seen a K7000 look this good in a long time. Usually, there is some thing that is a bit off. Like the vertical side of the image isn't straight or something. Only thing I can think of is that this is one of Ian Kellog's kits that I used.

And oh, as I was troubleshooting this chassis. I got a pretty good shock across the chest. Felt a nice thump from arm to arm. The monitor was discharged and was sitting for 30 minutes, sans chassis. When I went to hook the chassis back up. I leaned one forearm on the frame as I was putting the anode cap back on with the other hand. Z-z-z-a-p!!!! I'll never assume that a monitor even after discharge doesn't hold charge again. Will always discharge, even if already discharged.
 

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Hehe. It's a fun jolt, isn't it? :p Been there, done that. Yes, after you have discharged the tube and removed the anode cup, charge will immediately begin to rebuild. If you don't give something for the charge to bleed out into, when you go to put the anode cup back in you will become that path to ground.

Easiest method is to just always re-discharge the tube any time you are putting your hands anywhere near the neck pins or the anode cup. One could also just take some wire and hang it from the anode cup hole to the metal frame after the first discharge so that there's a constant path to ground for the building up charge. Honestly, however, if you've discharged it once you should have the tool handy so just do it again,
 
Yeah, lesson learned. Don't want to repeat that experience. I actually felt a thump across my chest. I can joke about it now.......since I am alive still.

On a happier note, I got two more working K7000 chassis as of today. One worked right off the bat. No work needed. But I do see some darkening around the resistor network so probably a good idea to reflow solder around there and all over. Caps look good on it as does the resulting image. The 2nd chassis was dead. Had a blown HOT and cold solder joints. Cake to diagnose and fix at this point. Gotta start throwing these in cabs now. Thank you Randy Fromm where ever you are for the flow chart!
 
Excellent summary of your work. At this point you're a chassis fixing machine. Thanks for sharing the results.
 
Thanks rob. I got a K7000A flyback from a member here. Will work on the K7000A 25" next. Here are the initial symptoms:
  • Dead w/good fuse
  • Low-to-Zero B+ voltage
Actions thus far, replaced HOT using a WG K7000's 2SD1398 HOT based upon what Ian Kellog stated in a thread I started long ago that it is close enough for use on a K700A. Still dead. Stay tuned.

EDIT: Misdiagnosed it. It is blowing the fuse along with the HOT, burrrrrrr. Will check C36 before even thinking about putting in a new flyback.
 
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Keep at it; i need a more local monitor repair source [emoji38]
 
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