RCA CTC...Something? poor HV output.
 

I'm not sure which CTC chassis it has. Originally I wanted an RCA to begin with, and I ended up with one today. I'm selling both of my Zenith's to Jim.

It's a New Vista set, Model GF 631, if someone knows which CTC this is, that would be awesome!

The high voltage is very poor. If the probe I have is accurate at all, the set is only producing around 12kV. It does display a picture, even though the voltage is poor. Adjusting the HV Output only changes it 1kV or 2KV, not much adjustment.

I don't hear any arcing in the flyback box, and there is some melted wax, but no carbon tracking so the flyback isn't arcing out. I don't have any spare tubes for this kind of set. I'd like to know where to start before I have to suffer the pain of ordering them all on ebay.

It worked fine about a year ago, and it's just been sitting since. I have all the pictures of it. I'll post them below.

http://img.photobucket.com/albums/v4...psehprkiuu.jpg
The pictures below show it was working a year ago and how it looked, a year ago.
http://img.photobucket.com/albums/v4...pslrswqyjf.jpg
http://img.photobucket.com/albums/v4...ps02nzdenz.jpg

I'd have kept a Zenith and dumped the RCA.....Tubes+PCBs=more frequent harder to fix troubles....As some one who runs an RCA(clone roundy) and Zenith(hybrid rect) side by side as daily watchers and has done so for 5+ years I can tell you that the RCA construction method/circuits are more of a pain to fix (and need to be more often) when they act up.

Depending on the chassis variant I probably have most or all of the tubes in my stocks. If it is a CTC-15 set I could probably sub known good tubes from one of my sets to test it.

If you have not tried the HV reg adjustment, then you should....If that don't help, pull the top cap off the HV reg tube (may need to place in a jar to prevent arcing) and see if the HV improves....If it does the reg needs work....If not suspect the HV rectifier on back to the H osc.

You have a CTC16 there. Any previous service information/parts replacement? If not then it's probably full of stock components.

Some might suggest a resounding "full recap!" I think that the capacitors in the RCAs of this era are actually quite reliable, but unless you're able to solve the low HV issue by swapping out the Horizontal Output, Damper, HV Regulator and Rectifier tubes then you're going to have to get a print and start checking voltages.

No idea. I was told the CRT is much newer, and it looks it by how it was working. It's an RCA "Hi-Lite", it has a few GE Compactrons throughout the set, all the HV tubes are still RCA lables, thus I presume original. I can get a stable, blurry picture out of it, so the horizontal output is working.

I have 4 Dentron 6LQ6 tubes that are still strong, the HF amplifier they lived in was still doing good strong power when I used it. I swapped one in, and the HV won't even kick in on these. It has an RCA 6LQ6 in it as is, and it's working fine.

That is bizarre. A weak Horizontal Output can cause HV issues, but you'll usually get a picture that won't fill out horizontally. I think it's safe to say your stock HO tube is doing it's job, but those other tubes you have should light up and run too.

And that CRT looks amazing too. You got a good one!

Are you running at full brightness? Will the picture "bloom" (defocus and expand) when the brightness control is fully advanced?

I can see NO WAY....you ONLY have 12KV here. The pix is WAY too good--and full. 12 KV would NOT give a full raster--and focus woulod likely be VERY bad..


YOU DEFINITELY need to check your HV PROBE !! I'll BET...from that pix...you are getting at LEAST 23KV.

I'm sorry. I did not mean to incite confusion.

The pictures posted first are of the set before the previous owner stored it. It does NOT display like this today. That is how it was. and should be...

http://img.photobucket.com/albums/v4...suqykawcm.jpeg

That is what I see on it, today. After about 15 minutes of on time, focus goes, then the picture fades out.

Take a look at the two 6GU7s on the far right end of the chroma board. Are their heaters lighting?

If not, with those heaters cold, here's what's happening: the plates go 'waay positive and drive the (G1) grids of the CRT positive (since the plates are direct-coupled to the CRT grids). The CRT beam current goes into avalanche, producing exactly the symptoms you describe. And this overcurrent is extremely hard on the 3A3, flyback, and H.output tube.
Don't run the set in that condition.

Of course if the 6GU7 heaters are lighting, then the problem lies elsewhere.

If the heaters are cold, it's caused by a broken ground in one of the two ground stakes on the far right end of the chroma board. So re-flow those grounds. This problem was endemic to the CTC-12, 15, 16, 17, and 25.
Even if the 6GU7s are lighting, re-flow those grounds anyway as a matter of routine.

I have the same set (ct16) and in my case the first symptom was the lost of converging adjustments in one of the color(green) hv was check and was detected at 17 thousand top, a few days later was at 15 and the poof. chassis was removed and all the voltages coming out of electrolytic tested ok. the high voltage transformer burned. it was replaced with a nos and all problems were solved.

what old coot88 describes happen to a friend of my ct15's or 16, exactly as he stated. he discovered by pressing down the 6gu7 and later pressing the board near the ground stakes thus making ground. an easy fix.

To add to Old Coots' post: there are two brown wires that run on TOP of the PCB between the 6GU7s and the 6GY6s. These carry filament voltage to 6GU7/6GY6 on right side, and due to heat, corrode to green dust where they enter the PCB hole.

Both of my 6GU7's heaters light up, and it appears the aforementioned connection has seen a reflow already. I tried wiggling them around a little, and nothing changes at all.

I also noticed there is a fair amount of arcing out of the top of plastic cup on top of the fly back box. The wire to anode goes in though there, as well as two others. I'm going to need to see what that's about. I'm sure that'll be worse once I get the HV back up.

The tubes are largely original, almost all RCA. I'm hoping I just have a flat tube. I'll add the 6GU7's to the check list.

http://img.photobucket.com/albums/v4...pszna6dy5q.jpg

Something tells me this tube shouldn't be so... crispy...and dark. The camera can't even pick up on just how bad it actually is looks.

This is the 6EL4 tube. It's also RCA original.

tube dark from xrays, just means had a lot of use, does not mean bad.

you should 1st try running the set with the CRT plug (the base socket)disconnected, this removes the load of a CRT which may be high due to bad CRT or incorrect bias.
Check HV

if no change, then try disconnect the 6Bk4, this takes the shunt tube out of the circuit, could be a prob if bad or bias is wrong.
check HV

if still no change
Check Horz out voltages, screen and grid
Check Horz out cathode current
Report back findings for whats next.

CRT plug disconnected: 14kv

6BK4 Disconnected CRT plugged in: 14Kv

I'll have to check the other two after my trip to see Jim.

I made sure I had a stonger connection with the probe today, the set is managing 14Kv

HV Regulator tubes use lead-impregnated glass to minimize X-ray emission. They darken with use.

I think people have posted before that the version B & C of those tubes are darkened
with a coating to help contain some of the x-rays they can produce.

With 14KV and the reg tube removed, that means its caused somewhere else. Be sure
the HV rectifier is good. Then check for the Possibility of problems in the horiz output
drive, or in the flyback. With good width is may be in the flyback.
A good place to start is the voltages around the H output tube. Also be sure to check that
the flyback is not getting too hot while on, check bias voltage on H output, and cathode
current.... I think a number of people here have been on that street before.....

.

oh yea forgot the HV rectifier.

with poor HV (with CRT unplugged) the SOP is to replace the Horz out,Damper,shunt and HV rectifier with KNOWN good tubes. You cant go by tube testers.

if those four make no difference the check the Horz out tube pin voltages.

This assume of course you have checked the B+ to know the power supply is ok.

there is one item worth mentioning, beginning I think on the CTC-15 there was an additional HV hold down circuit added. It works by take the rectified neg voltage from the blanker tube and feeding it back to the grid of the horz out thru a voltage divider. The Idea was if the HV shot up too high this hold down (the blanker got its voltage from the fly) voltage would bias the grid of the horz out more neg, cutting off the tube.

You can tell this when the grid of the horz out is TOO neg. esp if you have a scope and the wave form of the drive signal is normal (compared the neg reading at the grid).

what happens is the voltage divider (390k again IIRC) resistor on the chroma board loses its ground thru a very thin trace that runs right along the side of the board right by the HO tube. the trace cracks, the voltage divider no longer divides, and voila you get TOO much hold down. a simple test is to use the resistance charts for the blanker tube. if the grid resistance is too high its prob the crack in the board.

Okay. I got things to check then. I'll report back on my findings as I go along. I am out of town for the weekend so I will report back when I start to poke at this set again.

I'm really really hoping the flyback it self isn't bad.

The part I'm not understanding is; The picture is very bright, and I can turn the brightness up all the way and the screen doesn't bloom or go out of focus. In fact the focus is quite good.

When I play with the controls on the front, or change the channel, vertical conks out for a second or two before it pops back in. It struggles to hold vertical control as well. And while bright, the picture does remain quite yellow.

I wonder if my HV probe is just junk? Perhaps the problems are in the vertical section? Horizontal width is still good. And I can get a very sound horizontal lock.

I've swapped the tubes around a couple times with good ones, and still no improvements.

Would a stone cold dead 1v2 focus rectifier cause the issues the set is suffering from?

I tried to test it today, nothing glows inside, and it is fully dead according to the tester. I can't get anything out of it.

It actually had a 2AV2 in the socket. I still can get nothing from it on the tester with the correct filament voltage. It at least glows but does nothing.

I can get the needle to show something with the 3A3 and the other high voltage rectifiers, but this one shows nothing. Not even a little twitch.

I also don't think the socket has been modified at all to make a 2AV2 work.

1) bad focus rectifier gives bad focus !
2) your pix bright, full width, does not bloom.
The hoz osc, out, damper, rectifier, focus rectifier, HV reg
are all good. Your meter is NG, try it on another set.
3) arcing at the HV rect socket usually the cup. Other 2
wires are the filament & wrap around the FBT core.
ALL the wires are at full HV potential. & can arc anywheres.
4) Try a "by the book" grey scale set-up. then turn you attn
to the 6GU7 area of the set. Watch for dried up wires, they
were common even 45 yrs ago.
5) put up a few screen shots that show people & colorful scenes.
A pattern is fine but a real scene shows more.
6) the old pixs looked AWESOME so unless the jug has aged
fast & it happens, you will have a great set.
7) so you have 3 problems. Vert, arc & poor color. You should
get a first generation Sams for this set.

73 Zeno:smoke:

The focus does suck. So I ordered a NOS correct RCA 1v2 to replace the 2AV2, so it's a place to start. I'll look at the wires next and replace as needed.

Then I will set it on fire, and throw it off a bridge.

Don't set it on fire and throw it off a bridge. I can PROMISE you it won't fix the problem.

When you set it on fire and make it go off a bridge, do it in a cool way ! Put wheels on
it, pull it with a rope, make it crash into another set, set an explosion at impact, then
have the console go up a ramp, hidden by the smaller tv, explode at the top of the ramp,
spin in the air once or twice hit the ground & slide then go off the end of a bridge, crash
on the shore next to the water, and then explode again ! That would be Hollywood Cool ! !

Yah....... Oh, don't forget to film it from several directions, splice it into a really good
reel, and put it on youtube ! !

Yah......

And post a link to it too..... ! !

.

Or just give it to me. I'll go buy you a BPC set if you want to throw something off a bridge and whatnot.

Explode it and crash it off a bridge ! Don't tell TUD1 till it's over.....SShhhhhh......


.

:lmao:

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.

You got my DM last night? Lemme know what you might want. I might just commission you to fix the damn thing... I don't have the polethrea of parts you do.

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.

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.

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.

True, You might just want to set it on fire and throw it off a bridge ! !

:)

.

Well no all that has to be done is leave the fly in and it will do it itself.

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.

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.

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.