k4600 all red with retrace lines

jacklick

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so this monitor was working but colors weren't great and had never been capped. Did cap kit, removed and reflowed solder on header pins, restored tube (I would say it is still out of spec but there is life on all guns can pass cut-off tests etc).

Put everything back and things were looking good with decent picture. Then while adjusting or having it on the bench running for a bit, BAM! Red Gun seems to be stuck on and getting retrace lines.

Put tube back on CR7000 and, as before, there is some leakage on red gun during g1 short test but it is not shorted.
swapped p317 interface board with known working, same result. <this eliminates all the tr204-06 transistors
removed tr401-03 on neck board and tested with diode test == all tested good.
Reflowed solder on ground wire and tested all ground points == good

Any other hints to narrow this down further. Should I remove tr401 and see what the behavior is or is there an easier way to turn the red gun completely off safely?

this image is with black level about midway. If I turn black level all the way down it is just red w/ retrace lines


 
since I am on a 4600 mission...getting back to this one.

Swapped tr401 with tr403 and had no change. Red with retrace lines.
pulled and tested vr401 good.

kind of a pain but will likely try swapping neck boards to try to remove some variables.
 
Even though you reflowed the solder on the main PCB at the headers I would look for an open there just to be sure.
 
Even though you reflowed the solder on the main PCB at the headers I would look for an open there just to be sure.

good point. When I first powered up tonight, it looked fine on TPG for a split second so cold or bad solder joint might make sense.

I had just removed the neck board so will try different neck board tomorrow then check headers again.
 
good point. When I first powered up tonight, it looked fine on TPG for a split second so cold or bad solder joint might make sense.

I had just removed the neck board so will try different neck board tomorrow then check headers again.

Good luck. Seems like sometimes you get one that just fights back..
 
Ok so swapped neck boards and no change.

Then swapped chassis, with known working, and problem is still there, all red with retrace lines. Only thing common left is flyback and tube, I think. I have checked the tube twice and don't think that is the issue as it doesn't read with any shorts but can check again.

Might has well try a different flyback I guess or other thoughts?
 
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Chances are your tube is the problem. You mentioned that there was heater leakage too.
 
Read up on heater-cathode shorts (H-K shorts). There's a good writeup on the Sam's Notes/FAQ site (aka Sam Goldwasser).

got it reading now
http://repairfaq.cis.upenn.edu/samnew/tvfaq/tvcrtshorts.htm

Heater to cathode (H-K). The cathode for the affected gun will be pulled to the heater (filament) bias voltage - most often 0 V (signal ground). In this case, one color will be full on with retrace lines. Where the heater is biased at some other voltage, other symptoms are possible like reduced brightness and/or contrast for that color. This is probably the most common location for a short to occur.

Chances are your tube is the problem. You mentioned that there was heater leakage too.

I had leakage on the G1 short test (1st pic) but H-K was fine. Now it does show leakage on H-K but not necessarily a short (at least how I understand cr7000, which isn't 100%). This kind of makes sense as it was working and then bam red gun just stuck on.

Damn it...this tube didn't have a ton of burn either. shit crap piss etc.

Note: i have had several tubes with some "leakage" on g1 short test and they work fine. I have never had anything but full bars on the H-K short test so this stands out.
 

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Keep in mind the shorts can be intermittent, and/or come and go as the tube heats up, etc. They aren't always black and white (no pun intended) like solder shorts on a PCB.

The first thing that's recommended (per the Sam's page you linked) is putting the tube face down on a surface and GENTLY tapping the neck to physically dislodge it.

There are stories about TV techs blowing out shorts with a charged cap. I'm not an expert in this area. Maybe ask Buffett. Or see if maybe he has a video on it. (Have I seen him do one maybe? Can't remember.) Maybe it was Randy Fromm. There must be something on youtube.
 
I think that is how tube restorers fix g1 shorts. they isolate (would have read again what they isolate), charge a capacitor and then release that charge. That is why you have to wait for "remove g1 short" as the capacitor (inside the restorer) charges.

There are a couple other tests,Sam mentions, that I will try tomorrow as well. H-K shorts aren't handled by cr7000 or any restorer, tmk.

and thanks guys for the comments. Keeps me going.
 
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I have the same problem with a k4900 tube with the red gun. On the cr7000, the gauge would flicker a little on the g1 test. After zapping it at least 20 times, I gave up on it.

When it's working, beautiful picture. Randomly, the red raster lines would pop up. Shut it off, let it cool down, beautiful picture again.

I just use it now as a test tube, but may try tapping the neck method. Nothing to lose at this point.
 
I think that is how tube restorers fix g1 shorts. they isolate (would have read again what they isolate), charge a capacitor and then release that charge. That is why you have to wait for "remove g1 short" as the capacitor (inside the restorer) charges.

There are a couple other tests,Sam mentions, that I will try tomorrow as well. H-K shorts aren't handled by cr7000 or any restorer, tmk.

and thanks guys for the comments. Keeps me going.

I have a 4600 with H-K shorts on multiple guns. It's actually usable when on the bench but in the game where it's tilted back significantly the problem is much more evident. I haven't tried to do anything with it since at the time I didn't have any spare monitors and a wonky one was better than none at all.

The magnitude of my problem is modulated quite strongly by heater voltage. If you leave your tester on H-K shorts and change filament voltage (should be safe to move it up and down a couple of volts) you may see it drop into the red. It's also possible your chassis has a higher filament voltage than intended which could make it worse than the tester.

Since your short is on a single gun you can do the trick where you disconnect the existing heater circuit and instead drive it with a single turn around the flyback core.

https://www.repairfaq.org/REPAIR/F_monfaqa.html#MONFAQA_003
 
I guess it is intermittent after all. Motivated to try a few more tests and possible fixes, went to start working on it again a few minutes ago; CR7000 reads H-K short,the same as pic above before. Power it up and see dark screen a couple flashes of red and then dark screen. Turn on TPG and I have a nice picture.

Going to leave it on for 20-30 min and put it back on the CR7000. The tube is on it last bit of life anyway so I am motivated to experiment trying stuff but need the short to come back.
 
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Yep looks like the H-K short went away. Let it run for a good 45 minutes and then hooked back up the the CR7000. see pic for difference.


Want to put original (recapped) chassis and neck board back and will check again.
 

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Put the original neck board and recapped chassis back in. colors look decent. Still no H-K short.

Not sure if I was paying close enough attention before but there is has some constant "breathing". B+ is @ 125. Thoughts on the breathing, contracting / expanding of picture.

edit>>actually with screen adjust turned up just a bit, the b+ is down to @122.
 
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So what did you do to get rid of the short or did it just go away on its own?

It just went away. I powered the monitor up, it flashed red a couple times, snap, crackle, pop, and it was gone. Kind of disappointing, probably will come back when I put it back in game.

Also the breathing of image went away as well. I found a ground (neck board to chassis) that wasn't connected after putting original chassis back in, so powered it up and the "breathing" was gone. I disconnected that ground and couldn't reproduce it so likely wasn't the issue as gnd to dag wire was hooked up and chassis likely still gnd'd to frame. I will double check.
 
So before even getting this h-k short, I had started recording the restore and was going to film K4600 white balance procedure but the short derailed me completely. I went back today and tried to cobble together the footage prior to thread start and maybe make it useful.

 
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