Dead Tube?

R3LL1K

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Recently picked up an NFL Blitz Gold conversion in an MK cab. Looked at the chassis and noticed some bulging caps. Instead of recapping the chassis I threw in a working spare. Fired it up and I heard the HV but no neck glow. The other chassis was doing the same and had no blown fuses.

I figured it was the bad caps but after trying the working chassis I decided to try the pulled chassis with bulging caps on a tube I have handy. Hooked it up flipped the switch and it came right up. It has jailbars but works. First time I've encountered a dead tube.

Is this something that a rejuvinator might fix? Has anyone encountered a similar situation and brought the tube back from the dead?
 
You could Ohm the two heater pins just to see if it's open.
A rejuvenator could check this, but won't fix it if it's the heater.

Personally, never seen a "dead" tube.
Usually just a color gun maybe.
 
ohmsss

First check the heater pins and see if they or one is bent over and not going into the socket.
measure the two heater pins and see if you have around 2-6 ohms.
 
First check the heater pins and see if they or one is bent over and not going into the socket.
measure the two heater pins and see if you have around 2-6 ohms.
I'll ohm it out when I get home.

Thanks for the replies. I have a BK 470 but sadly haven't gotten around to making the adapter yet. Is this something that would have been easier to troubleshoot with a tube tester?
 
I have only seen one bad tube. All guns were reading zero on my rejuvenator and I could not get them up after repeated zaps. chassis worked fine with another tube...
 
Hooked up the tester to it and when I set the heater voltage I can see the neckglow. Other than that all of the guns read bad. Followed the instructions to remove shorts and rejuvenate and I still get bad readings on all the guns. Hooked the chassis back up to the tube and no neck glow or anything. Any suggestions? Heater voltage is set to 6.3.
 
If the neck glows when the rejuvenator is hooked up, and you have HV but no neck glow, you've probably got a bad heater circuit. What chassis is it? Sometimes there's a resistor on the neckboard in line with the heater that goes bad. Otherwise, maybe the heater winding on the flyback is bad. But if you have HV, you could probably wind your own heater (search the forum for isolating heater voltage).

DogP
 
Swapped tubes and same issue. Checked the voltage coming from the iso and it's fluctuating between 130 and 131 volts. Bad iso? Would the higher voltage cause the monitor from not doing anything? I have a spare iso so I can swap that out but if anyone has any suggestions as to what else it could be let me know. TIA
 
What do you mean by "Swapped tubes"? Same chassis on a different tube, or swapped complete monitors? If you've got 130V at the monitor, and the monitor has HV, then your iso is fine.

And when you say you've got HV, are you sure it's not giving HV for a split second at startup and then going into shutdown? That would cause no heater. If you watch the heater when you turn it on, do you see it start to glow and then shut off? And do you hear the HV discharge when you turn it off (or do you get a snap when you manually discharge it)?

What model is the monitor?

DogP
 
If you have a 19" K7000 and are running 130 into it, it MIGHT cause a problem, as the regulator is a 123v regulator. I did have one issue where the AC was 135 out of the iso (with 120 in) on a Williams cab. Once I got a better iso, I stopped having problems (and losing parts).

It's possible your monitor is going into HV shutdown, as a higher input could be causing a higher B+, but you'd have to check it to make sure...
 
What do you mean by "Swapped tubes"? Same chassis on a different tube, or swapped complete monitors? If you've got 130V at the monitor, and the monitor has HV, then your iso is fine.

And when you say you've got HV, are you sure it's not giving HV for a split second at startup and then going into shutdown? That would cause no heater. If you watch the heater when you turn it on, do you see it start to glow and then shut off? And do you hear the HV discharge when you turn it off (or do you get a snap when you manually discharge it)?

What model is the monitor?

DogP

Monitors are 25K7191's

The process so far has been this.

Brought game home playing blind. Checked voltage coming from iso and it was 130v. Since monitor was obviously getting power I decided to swap out the chassis with a known working one. Swapped out chassis and got the same issue, nothing on screen and no glow.

Swapped tube in game with a known working tube from my test bench so I now have a known working chassis and a known working tube in the game cabinet and nothing. Test tube pulled from the game cabinet on my test bench and it fires right up.
 
Try running the monitor power from your test bench to the one in the game. If it fires up, then you know it's the too-high iso output.

Could also be hogged out pins in the power connector...
 
Traced the video wires from the Jamma harness to the connector that goes into the chassis and they were spliced mid-way through. When they spliced the wires they ended up leaving the ground wire out and putting synch on ground and synch. Fixed this and I now get video on the monitor.

The video has issues though. :(

I'll post a video in a bit.
 
Heater voltage is something that comes right off the flyback on a K7000 (and most standard res monitors). It should work independently of signal.

But I'm glad you got things sorted.
 
Heater voltage is something that comes right off the flyback on a K7000 (and most standard res monitors). It should work independently of signal.

But I'm glad you got things sorted.
That's what I thought and am used to seeing as well. Strange situation indeed. I have powered on cabs with no PCB in them and gotten neck glow yet for some reason I couldn't get anything from this one without putting a signal to it.

I'm thinking there might be a ground issue or something. Doesn't make sense but it could be the reason that there is an issue with the video now. You can see the game running but there is horizontal lines running through the picture.
 
Horizontal lines?

If the picture is too bright you'll get retrace lines showing up... Also, if the chassis is out of whack you may get a weak picture with poor contrast and retrace lines.

Pics please.

RJ
 
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