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  #31  
Old 10-13-2015, 07:46 PM
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Quote:
Originally Posted by Electronic M View Post


A bad focus rect. tube will cause bad focus. One thing you could do while you wait is go to Radio Snack (if one still exists near you) and get 4 of the 1.5KV diodes they sell, and string those in series as a SS focus rect......IIRC roundy focus voltage is ~4100V so 6KV worth of diodes should be able to take it....Maybe add a 5th or 6th for good measure.
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  #32  
Old 10-15-2015, 11:33 PM
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For lack of anything else to do, I poked around with the set for about a half hour. I cleaned the high voltage wires to check where they were arcing from.

And I let the set run for about 15 minutes, while I checked and watched a few things.

Nothing changed so I shut it down, checked the caps, nothing was hot, everything was cool to the touch until I checked in the flyback box...

The flyback is getting extremely hot. So much so, that I could see fresh wax dripping out of the bottom of it.

I presume that means it's shot? Internally shorted or something like that?

On a positive note: I emailed the guy I bought it from, and explained my situation, and he's giving me a complete CTC16 almost identical to this one with a bad CRT. I'm going to lay claim to the flyback for my set, but I will likely part the rest out for other's who need RCA parts.

Last edited by Arcanine; 10-15-2015 at 11:48 PM.
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  #33  
Old 10-16-2015, 02:35 AM
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Have you used the H lin./H eff. coil to dip the cathode current? That is an essential procedure on RCA sets......If the adjustment is far enough out of whack the H out tube could be drawing enough current to badly overheat the fly....And RCA ran their flys hard, usually close to the point overheating.
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  #34  
Old 10-16-2015, 07:03 AM
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yup could be H eff coil if not checked it could be standing at 250ma right now and that would be a real cooker for the fly. and i noticed that whenever a hot tube is swapped the ma changes a bit and should be checked whenever anything is done in and around the horiz section. i have a 66 silvertone that i recapped and played flawless only problem was it would drip wax and the fly would get really hot and still played fine with the eff coil at 190ma so having a nos fly i replaced it and it never got hot again. it was only a matter of time that the fly was going to take a dump. it seemed to me that the secondary, the donut, was shorted somewhere enough to heat it up to the point of melting the wax but not affecting the operation of the set. i would check the eff current and associated components around the horiz and if all is good, change the fly, well saying that is easier said then done being these flys are hard to find.
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  #35  
Old 10-16-2015, 08:23 AM
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True, You might just want to set it on fire and throw it off a bridge ! !



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  #36  
Old 10-16-2015, 10:19 AM
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Well no all that has to be done is leave the fly in and it will do it itself.
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  #37  
Old 10-16-2015, 02:40 PM
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http://www.boxcarcabin.com/rcacathode.htm

Is this an effective method of checking the cathode current? I did some research on how to check this, since it's important, and I may as well know how to do it.

I plan to check this later after I make my trip to Milwaukee to get the parts CTC16.
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  #38  
Old 10-16-2015, 03:37 PM
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That is a good procedure (sam's excerpt I believe). I generally do the HV adjustment after the fact. If I've adjusted the osc. that way once, and it has not failed or significantly drifted since I skip that part, and only do the cathode current.

I prefer an analog meter (I just use a Radio Snack cheapie) for this as it allows a more precise dip to be achieved. If it don't want to dip below 220mA something is probably wrong. 185-215mA is where you want to be to baby that hard to get fly.
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Old 10-16-2015, 05:34 PM
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That boxcar guy has a lotta cool stuff if you fish around there.....

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  #40  
Old 10-16-2015, 05:52 PM
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That boxcar guy has a lotta cool stuff if you fish around there.....

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He is a member here....IIRC his handle is CTC17.
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  #41  
Old 10-16-2015, 06:03 PM
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Ctc17 has been gone for awhile now.
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  #42  
Old 10-17-2015, 09:17 AM
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Quote:
Originally Posted by Arcanine View Post
http://www.boxcarcabin.com/rcacathode.htm

Is this an effective method of checking the cathode current? I did some research on how to check this, since it's important, and I may as well know how to do it.

I plan to check this later after I make my trip to Milwaukee to get the parts CTC16.
Easiest is using a socket adapter for the 6JE6/6LQ6 and a 300-500mA analog meter. I have a center zero one, so hooking up requires no polarity. The adapter is a Pomona 2599, and breaks the cathode circuit for you-available on eBay and other vendors.

Make sure you have a spare horiz efficiency coil - mine was seized, so i swapped coils before I started. 112875 is the part number.
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  #43  
Old 10-17-2015, 11:05 AM
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Quote:
Originally Posted by Electronic M View Post
I prefer an analog meter (I just use a Radio Snack cheapie) for this as it allows a more precise dip to be achieved. If it don't want to dip below 220mA something is probably wrong. 185-215mA is where you want to be to baby that hard to get fly.
Yes, an analog meter is imperative since digital meters are prone to going nuts on complex waveforms. We just used a Simpson 260 and a Pomona adapter for the cathode current.
Since we were an RCA dealer and the first imperative was keeping the damn sets working thru their warranty period, we put the power xfmr. primary tap for 'high' line voltage, and the H.out cathode current as low as possible, 200-205 ma. max.
210 ma. would have been the absolute upper limit for any degree of longevity.
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  #44  
Old 10-21-2015, 07:27 PM
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I'm starting to think my HV probe is lying to me.



I swapped a couple tubes tonight with the CTC20 just to see, and I swapped in my NOS 1V2 focus rectifier and this is what I saw when I went around to the front of the set. A little tweak to the focus adjustment, the picture is razor sharp, my camera won't even catch how sharp it actually is.

This is the first time it's ever given me a color image.

It's also very bright and clear. I let let it run for 10 minutes on the dot and shut it off, and checked the fly, and it wasn't even warm.

I'm starting to think it's not the fly and more dead caps. It refuses to fill the screen vertically, and when no color is present, the image still looks yellowish. As soon as color pops, it looks good. It has full horizontal and locks on with out much fuss.
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  #45  
Old 10-21-2015, 07:38 PM
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I TOLD you...you were NOT that low on HV...now I am SURE of it !! That pix looks like at LEAST 24KV to me--maybe MORE.

Was one of the tubes you changed the H-osc tube or damper? A weak osc tube WILL allow way too much current through the fly, lower HV and overheating. As others have said--you DO need to check the H-drive current level now--to make SURE it is under 220 MA. Cool fly tire and core or NOT...you NEED to KNOW.
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