RCA CTC 38 burnt resister - Videokarma.org TV - Video

damen · #1 09-24-2009, 07:43 PM

I am trying to figure out what the value of this resistor is I can not read it on my old worn sams it is right over the HOT tube next to the HV Regulator Diode I put a red arrow to show the one if anyone knows or has a sams that they can tell what it is I would so aprisheate it. The chassis is a ctc 38xp Model# GL 692 S

freakaftr8 · #2 09-24-2009, 08:52 PM

Pull one leg off and ohm it. What do you get.. Then as you are ohming it hit it with freeze spray and see if it drifts.. If so then it's probably bad.. One of these guys im sure have a sams.. I only have a CTC-17 and the chassis is much different.

andy · #3 09-25-2009, 01:34 AM

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Findm-Keepm · #4 09-25-2009, 06:13 PM

Something isn't right, at least from the picture.

Looking at the Sams (CTC38 folder is in Photofact set 1000), the resistor appears to be tied to the HV regulator diode (black epoxy body with a white band on the end to the right of the burnt resistor in the picture). The cathode (white band end) of the diode is tied to the 375V "A" source by the fact it is tied to the 220K (red-red-yellow) resistor that is seen in the picture. The other end of the 220K resistor is tied to one end of the Color Killer control, right?

If the diode to the right is the HV regulator diode, Sams shows the resistor on the anode end to be a VDR, which the picture doesn't support.

What does the resistor connect to - the HOT, or the damper? If so, what pins (pins are numbered in clockwise fashion looking at the bottom of the socket) is it connected to? Are there wires connected to the same terminals? If so, where do they terminate?

Anybody have a Sams folder they can send to our friend? Mine is very shopworn and incomplete.

CTC38 sets were quite ubiquitous - I'm familiar with them mainly from a parts standpoint - I must've sold a ton of flybacks for them (RCA 119834) back in the early 80's. I've changed a few as well.

Give me some more info and I can help - but the pix tells an incomplete story.

Cheers,

damen · #5 09-25-2009, 10:02 PM

Thanks for your help on this guys. Here is a scan of the sams my scanner is to small to do a full shot. The more I have looked at it I to think it just don't show the exact same set up as mine the picture is so poor and faded it is hard to tell and the schematic seem to show one side of that diode going to ground and the other to a VDR and that is not the case on my chassis. Whats bad is when I got the set I replaced the resistor with a 100 ohm resistor and can't find the one I pulled it looked like that was what it was but being burnt I could have been wrong. The set does work well and has a good picture but the flyback seems to be running a little hot quite a bit hotter than my CTC 7 set so I just want to be sure that is the rite resistor. That resistor has a wire on the diode side that goes to the pin 9 of the shunt regulator and the other side is going to a 8.2 m ohm resistor to pin2 of the HOT and yes the 220k resistor on the white band side of the diode is going to the color killer.

bgadow · #6 09-25-2009, 10:35 PM

I should have a spare; if you want it mailed to you just send me your address.

freakaftr8 · #7 09-25-2009, 10:41 PM

Guess the only thing you can do and go by is all measurements for the flyback, check HOT cathode current, and neg bias voltage. See if everything is kosher.

damen · #8 09-26-2009, 12:08 AM

I found the resistor that came out of there and it tested 725k ohm You can clearly see the brown band and that the next one over is black but the third ? I removeed the 100 ohm and replaced it with a 1.0 k ohm whitch tests at 990k ohm on my meeter I feel like that is what it should be since that is the closest thing to that value with those colors the set still works verry well I was going to test the hot cathode MA but found that the hoizontal effishency coil is frozen anyone know a good way to unfreeze it ? I will probly just have to check with Moyers and see if they have one. The flyback seems to be running a little cooler It was just a little warm after 30min but not hot. I still want to get or fix the coil and check to see that everything is what it should be.

damen · #9 09-26-2009, 06:57 PM

I have tested the HOT cathode it tests at 213.09 I wish I could adjust it up a bit bit the sams shows 220 but it is stuck and will have to be replaced it's not broke but I tried every thing and even got a good hold on it and the adjustment tool finaly slipped a notch. I don't know how to check the neg bias voltage never done that before. Anyway I will try to locate a coil or if anyone has one or knows where to get one let me know. Thanks for all the help all.

freakaftr8 · #10 09-26-2009, 09:11 PM

Leave it. That's ok if it's around 213ma. Better to not mess with efficency coil. It will most likely break the slug if you force it anyway. The brown band can always b a result of the resistor being scorched. I have seen bands on resistors that were burned look brown later to find out it was the color red or yellow or violet. And be careful putting resistors in there that are notthe right rating. I've made this mistake too before.

freakaftr8 · #11 09-26-2009, 09:13 PM

Oh and some flybacks get warm. You should feel the one on my CTC-40. It's scary

old_coot88 · #12 09-26-2009, 10:21 PM

If the cathode is running 213 ma, be happy. You certainly don't want to raise it, regardless of what the Sams says. The eff.coil adjustment is intended to dip the current, not raise it. I woulda been happier with 200-210 ma, which will give longer HOT and flyback life.

The grid voltage is measured with a high impedance meter like a VTVM or a FET type multimeter.
Bill(oc)