K7500 intermittent shutdown

mecha

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monitor in our Carnevil goes into HV shutdown even after removing the HV Shutdown pot, so does that mean it's not an HV shutdown thing and it could be something else?

as I've mentioned in other threads, I've never measured or adjusted B+ before, and the K7500 is finnicky with B+ supposedly.

this monitor has just been re-capped and I reflowed the AC header for fun.

I had a K7000 lose neck glow and the CRT would shut off and it would come back if I tapped on the frame, but it's not happening on this one, not sure if the heat circuit could be of any interest?

please help. thanks. :)
 
If you have no HV shutdown pot installed, then you'll have no HV. That is not the way to disable the HV shutdown...
 
I didn't think so, but I had a tech that told me him and some other guys did it on 7900s. lol

nonetheless, it worked the same exact way as it did with it installed.

this still doesn't help any.
 
hv

Does the cap kit include the two caps by the hv shutdown. I have found them bad(esr) with this problem.
But, I have found this the solution more then the other is that the factory adjust them to shutdown and then tweaks them back just a hair so they are close to shutdown but wont.
After a few years things change and it starts to shutdown, so tweak the pot alittle. It always seem that the ones that went into shutdown were always glued in a certain spot and the ones i saw that did not shut down were glued in another spot, but always the same. It seem like they had two people,one that like to put the pot right before shutdown and another guy who gave a little more room so it did not go into shutdown.
 
I grabbed a donor pot off a non-working 7500, it was in the same position. since it still has the original glue on it, it's probably going to be a challenge to make such an adjustment. does it make sense to pull the whole knob off and spin the wiper and then reassemble?

btw, which way do I turn it?
 
From what i remember the pot was pointing to about 10-11 o'clock and it needs to be about 8 o'clock. I forgot what the ohmage is so i go by that now.
 
I tried testing it from both legs, the old pot and the new pot (before I removed it entirely) were of different values, think one was a 3.6 and the other was a 4.03, and the old pot I couldn't even really get a reading from the other leg, while on the new one I think it was about 6.-something. it's a 10k pot, so..

is there a reason why Wells says that if you adjust it, it has to be re-sealed with epoxy? is that so that no accidental adjustments by hand happen, or does it seriously walk on its own over time?
 
It's just meant to not be adjusted once set. If set too high the monitor will not shutdown and could be producing x-rays and such.
Sometimes the glue they use has a tendancy to be conductive though and could be causing a premature shutdown.
If you swap the pot, set it close to the one removed and you should be fine.
I know the few 74/7500's I've worked on seem to have the glue strewn all over components in that area, made even removing those two electrolytic caps in that area a pain because of it.
 
now that I remember, maybe there was a cap I missed, or maybe it wasn't in the kit, cause the pot was actually stuck to a nearby cap.

I wonder if that could be the problem? I had some leftover, some were for a 27" pincushion board, I saved em, but I think I had 1 extra. I was crossing them off the sheet as I installed them, but the fiance was rushing me at the end, so maybe I missed one.

EDIT: also, what about the B+? should I measure that and see if it's running too high? I don't even have the G2 set that high, but I have to step it up a little bit because it's a gun game and it won't work right otherwise.
 
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Definitely want to keep tabs on what the B+ is doing.
If it's spiking high causing the shutdown then there's a problem elsewhere still.

I have a 7400 that's still causing me similar issues, been racking my brain on it and changed so much crap out it's rediculous. (7400/7500's seem to have similar issues in this area)
 
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