Groovy CTC-15

[bgadow]

My -15 had the short vertical problem which took some looking but finally I found an open resistor, it was right off of either the height or vert lin. control, I can't remember which, but worth checking.

[andy]

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[Charlie]

Originally Posted by bgadow

My -15 had the short vertical problem which took some looking but finally I found an open resistor, it was right off of either the height or vert lin. control, I can't remember which, but worth checking.

That's exactly what was wrong with this one. R105 150k ohm connected between the height and vert centering controls was open. Changed it and the raster opened up nicely! One problem solved... several to go!

I got the rest of the lytics changed last night. Almost a pain trying to figure out where to put them all. Those 80/450 caps take up some space!

Those two tubes that wouldn't light turned out to be a wire on top of the board that had corroded and broke. New piece of wire fixed that.

Today I am going to removed the crt so I can get all the crap cleaned out from behind the safety glass. It should fall right off.

Three other problems I've noticed so far. It seems that I have very little control on the brightness. It's displaying the picture at a "normal" brightness level it seems, but, I can't make it much brighter or darker. It will change some, but not like it should. Checked the control with my meter... it checks good. Any suggestions on that?

The picture will lock on the horizontal when i first turn on the set (with the control turned all the way to one side). Touching anything... whether it be changing the channel, adjusting the controls, or simply breaking wind will cause it to get out of whack. The only way I can get it to come back is to turn it off and then back on. Tried two different horz osc tubes and no luck so far.

The service switch fails to function conrrectly. I don't get anything on the screen when in the service position. I had to remove the verticle output tube for setting the screen controls.

Can't say much for the color right now. I think I saw it get color a couple of times, but, I'm not going to concern myself with it till I get all the other bugs out.

It's getting better... slowly but surely.

[drh4683]

Charlie,

Very nice set! Its called the "VISLANDA" (CTC-15AA). Sounds like you have low boosted B+ and I think that can be caused by a leaking cap (.01 @1KV or so) or a leaky diode. B+Boost should be 1100 volts. B+Boost feeds the CRT screen controls and if low in voltage, you cannot produce horizontal line in the service position, even with the controls all the way advanced (depending on how the voltage is).

[Charlie]

Was really rainy,cold, and nasty here today, so I spent the whole day in the garage trying to make heads or tails of the problems I've got on this set.

After an entire day, and damn-near rebuilding the deflection board, I finally got the horizontal to lock... and it seems it had nothing to do with all the caps and resistors I changed. In fact, I felt like a dumbass once I figured it out. No, it wasn't a tube... I wouldn't even admit to that. The only reason I'm gonna mention this is because it just goes to show how simple a problem can be... especially when we beat ourselves over the head trying to figure it out.

Changing the caps and resistors never made any changes on the screen. It acted the same way with the new parts as it did with the old parts. Finally, I gave the horz osc / waveform coil a half turn to the left, and everything locked perfectly! Damn! That's all it needed! I had never even considered that coil because I would have suspected that coil would never get touched by anyone. Well, guess i was wrong. So, now it locks perfectly.

Still has the brightness problem... kinda on the dim side and changes only slightly while turning the brightness knob. I changed the caps and resistors Doug mentioned, but no change. I then changed many resistors and caps near the 12BY7 tube. That seems to have made a little difference Now i get a very faint red line when I move the service switch to the left... before i got nothing. In fact, the faint red line doesn't quite make it all acorss the screen... only part of it. Oh well... it's a start in the right direction. Also noticed the plate voltage on pin 7 is low. Supposed to be 310 volts and I get about 240 volts.

Before I finally quit for the night, I noticed the burst amp 6EW6 shows voltages way out of whack. The worst pins were 5 and 6. Pin five should have 50 volts on it... instead it reads about 395 volts. Pin 6 is supposed to have 265 volts, but reads 400 volts. Damn... that's way off!

Well, I'll be back on the bench tomorrow with it. Supposed to be rainy again.

[Charlie]

It's been over a year since I last played with this set. My new-year resolution was to FINISH sets I've already started on... instead of starting on new ones. So, last night I decided to put this one back on the bench.

Last time I ran it, I was having a video problem. I had changed several resistors that were off spec with no luck and also tried 3 different 12BY7's. Well, it seems those 3 tubes really bit me in the ass! Come to find out, none of the three tubes were any good! I took one from a working set, and the video came back!

After I got the video last night, I started making adjustments here and there. I broke one of the convergence pots... great! Had to change the 6GH8 to get color to come in and it played "okay". The color level control seems to have some dead spots in it, so it will need changing. However, when it's turned up, the colors are quite rich. Then I went to bed.

Today, I turn it on and now have an odd problem. The picture is rolling... horizontally! I don't think I've seen that before in a set. Tried changing the sync and horz tubes (with tubes from another set) and it doesn't help it any.

Any thoughts on a picture rolling sideways???

UPDATE: Picture rolling sideways was due to a bad solder connection at the sync tube socket.

I'll still be needing to make various adjustments, clean some controls, replace the broken convergence pot. I'll get a picture posted of what I have so far later this evening.

[Charlie]

Here's the photos I have so far.

Although I have video back now, the brightness still lacks a little. I have to turn the control nearly all the way up to get a comfortable degree of brightness... and also must have the CRT bias switch in the bottom position for a weak CRT... but yet the CRT tests just fine. All voltages at the CRT socket are pretty close to where they should be.

The focus isn't very sharp. However, the focus voltage is right on the money. High voltage is good as well.

I'm noticing that the AGC control is working more like a contrast control. Of course, it's kinda supposed to be a course contrast control, but the signal does not fade out all the way when turned to the left, and it does not overload to the point of pulling the picture if I turn it to the right. It simply gives more or less contrast.

One of the initial problems I noticed last year was the service switch will not produce a horizontal line... and this year is no different. If i put it in the service position, it simply cuts off the picture. No line.

I'm a little dissappointed that it's not playing better than it is. I've changed a lot of resistors that were way way out of spec. All the lytics have been changed as well. Nearly all of the caps on the boards are orange drops. I left those in. There was a small handfull of cheesy caps, and I've replaced them.

I guess it's likely many of these issues are related. If anyone has suggestions, please speak up.

[RVonse]

Here are some of my thoughts. I would continue checking voltages around the 12BY7 against the values on the schematic. And I presume you have already changed out the capacitor supporting contrast control which hooks up to the 12BY7 cathode?

On the focus, I would first verify the small rectifier tube but it seems a little suspicious that you have changed out a flyback and are experiencing focus, possible boosted B+ problems, plus a brightness control issue. They could all be related to not having correct boosted B+ which originally comes from your new flyback. If I recall the the crt screen grids are ultimately sourced from this same voltage. You did say the screen grids were showing the correct voltages? I agree with the prvious poster to check boosted B+ with a fine tooth comb.

Your picture tube looks really nice and you have done a lot of good work so far.

[blue_lateral]

Charlie-

Regarding your earlier post (way earlier) about horizontal lock, my 15 had a problem that required twisting that coil to warp things back to the correct frequency.

The symptom was this: To set things up you are supposed to short the sync test point (to kill the sync) and short out the sinewave winding of the horizontal oscillator coil. You then adjust the horizontal hold to make the picture stand straight up.

This is the part mine wouldnt do. "Straight up" was off one end of the control.

When you have that, you remove the jumper from the sinewave coil, and adjust the sinewave coil until the picture stands straight up. Then remove the jumper on the sync point. Picture should lock.

It about drove me nuts. I thought that some component in the oscillator had to be at fault. Not so. It was the .0015µF mylar drop that couples the oscillator to the horizontal output. It had gone way up (!) in value. I have an old book around here somewhere that says a common failure was for this cap to go down in value, and the symptom was burned up horizontal outputs or flybacks, due to reduced horizontal drive. If you havent replaced this cap already, maybe take a closer look at it.

Regarding the "too dark" symptom. Have the video tubes been checked for gas? These sets have partial DC coupling all the way from the video detector to the CRT. A little grid current can screw the brightness all up.

All the best,

John

[Charlie]

Vislanda is a town in Sweden. Here's part of an ad for a RCA Vislanda.

[bgadow]

I had some color-sync problems with my -15 as well. I could get it to lock with the jumper but not without. For awhile it would lock after running for about 5 minutes. Then, somehow, it stopped acting up and now it always stays locked.

[kx250rider]

(color sync problem) ... Shield cans on 3.58 osc & burst amp. I had this loss of color sync lock several times on CTC-15 & 16's where a troubleshoot did not reveal any problems, and was usually able to resolve it by moving the shield cans around on those tubes, or replacing them with another style. It's DEFINITELY not a technical repair, but it worked for me

Charles

[Charlie]

I've been spending lots of time with this set lately... and seems I'm not gettin very far with it. I've changed many resistors around the 12BY7... actually all of them. The 22K 2-watt resistor was reading 38K. Changing it helped a little, but not enough to bring the brightness up to normal. It's still dark. Also changed some capacitors.

I swapped the 12BY7 with the one in my Curtis Mathes... made no difference.

As far as voltages go, everything is pretty close to where they should be. The voltages on my CRT are right on the money. SCreen voltages are healthy... cruising about 820 with plently left to spare if I crank them up all the way. So it's apparent that the boosted B+ is good.

High voltage is good and the hz output is cruising at 202ma.

Still cannot produce a horz line with the service switch (no matter which position the CRT bias switch is in). I checked and changed some resistors near the switch... no change.

The only way I can get good brightness is by placing the CRT bias switch in the bottom position, but I shouldn't have to do that since my CRT test excellent. Picture quality is pretty good while in that position.

I have a B&K Analyst 1077B that i'll probably dig out and try. I've used it twice before on blk & wht sets, and both times it helped me pin-point video problems really fast. Hopefully it will be able to help with this set.

[Charlie]

Oh... something else to mention... When I turn the set OFF, the brightness comes back for an instant as the set powers down.

If I'm not mistaken, Southernguy has a roundie that's doing the same exact thing.

[Charlie]

...which is more than I've made in a couple of nights!

I found a 68k resistor on the rear of the bias switch... reading 276k. With such an increase in value, I had hoped changing this puppy was the ticket... but it wasn't. It did give me more brightness, but I still cannot produce a line on the screen. Damn!

The brightness came up enough that I can put the bias switch in the middle position and almost get a nice picture... however it still requires cranking the brightness up all the way.

At least I got that! I feel a little better now!