Stabilizing a TS-18

[Zenith26kc20]

Have started on my basket case 8 inch TS-18. Got the high voltage up last night and have a question. My TS-4's (both) are not the most stable during warmup. Has anyone tried to make the horizontal oscilator stage more stable?
I have done this on some other Motorola's by using 1600 volt capacitors in the vertical and horizontal stages but it doesn't seem to work with the TS-4's
Since the TS-18 is nealy identical I was curious. Reaching behind to adjust the horizontal constantly is a bit of a pain.
And this one is a BASKET case! No knobs, back and missing a good number of parts. I kept it because the CRT is perfect!

[compucat]

Originally Posted by Zenith26kc20

Have started on my basket case 8 inch TS-18. Got the high voltage up last night and have a question. My TS-4's (both) are not the most stable during warmup. Has anyone tried to make the horizontal oscilator stage more stable?
I have done this on some other Motorola's by using 1600 volt capacitors in the vertical and horizontal stages but it doesn't seem to work with the TS-4's
Since the TS-18 is nealy identical I was curious. Reaching behind to adjust the horizontal constantly is a bit of a pain.
And this one is a BASKET case! No knobs, back and missing a good number of parts. I kept it because the CRT is perfect!

I sure would like to find out about this myself because the set in my avatar is my beloved Motorola 9VT1 which uses the TS-18 chassis. My problem is the vertical hold drifts during warmup and yes it is a pain to reach behind the set to adjust it. I can't understand why Motorola put those controls in the back when they are prone to drifting and nearly every other brand of set has them in front. What were they thinking? I know these sets must have needed frequent adjustment even when new.

[Zenith26kc20]

I've wondered the control placement myself. I have my TS-4J vertical OK but the horizontal is wild for the first 15 minutes!

[Eric H]

They really shouldn't be unstable if they've been recapped.

I would suspect a drifting resistor in the Horizontal or Vertical circuit (depending on which problem you are having) They use half of a 12SN7 for Horizontal AFC so I would check closely around that tube for a problem (the tube itself could also be the problem).

Sometimes heating the resistors with a soldering iron will quickly expose the ones prone to drift, you can do that with the Mica caps too but don't get carried away and melt them.

[Zenith26kc20]

on my first TS-4 every cap and high value resistor was changed. The rest were checked for tolerence. Once warmed up it'll even play a Betamax without "flag waving". Since the TS-18 is in such poor shape, I hope to track this problem down once and for all.
While I'm asking questions, years ago the Motorola factory tech said that once these little sets horizontal frequency "went south" nothing could get it back. When he died I bought the five sets from the Motorola distributor. One of them had the terminal strips all cut to separate them and hacksaw cuts in the base of the CRT between pins. I tried the CRT in my other TS-4 and it gives a good picture. This TS-18 is in that lot. Has anyone had the horizontal frequency fight them like he described? Like I said, it's a real mess! At least the high voltage bit me good last night!
I have a good deal of the update literature from Motorola and there is no mention of the horizontal going so far off value that it posed a severe problem.

[compucat]

Originally Posted by Eric H

They really shouldn't be unstable if they've been recapped.

I would suspect a drifting resistor in the Horizontal or Vertical circuit (depending on which problem you are having) They use half of a 12SN7 for Horizontal AFC so I would check closely around that tube for a problem (the tube itself could also be the problem).

Sometimes heating the resistors with a soldering iron will quickly expose the ones prone to drift, you can do that with the Mica caps too but don't get carried away and melt them.

In my case the set is completely recapped and all the resistors in the sweep circuits and high voltage were replaced. The set has been very reliable but the vertical hold has always been prone to drifting for about the first 15 to 20 minutes of use. I wonder if this is just a design characteristic that was to be expected in an economy set of this vintage.

[Zenith26kc20]

Just ordered the caps for the critter. We'll see what happens!
Since I "bounced" off a ladder a few weeks ago I've had a lot of time on my hands. I was looking at my Motorola book on the TS-4's and the book shows the second anode on a tap in the vertical centering control. My TS-4 J and my TS-18 have the anode going to the 100k from pin 2 of the 1B3. Has anyone seen the connections from the centering control?
Also, I read on another thread about R-84 in someones set being 470 ohms. The schematic shows 100 ohms. My TS-18 does have the 470 in it! It appears factory.
Now a good question. What is the earliest TS-4 that anyone owns? My schematics show a TS-4B (the one with the 7F8 in the tuner) as the earliest one?
And more questions! My TS-18 does not have the 6SN7 set up as the horizontal AFC diode. It does not have (never did from appearance of the internals) T-4. It is hooked up with the standard sync input like the TS-4's. Any guesses?

[bandersen]

As far as I know, I own the oldest TS-4 The chassis is just stamped TS-4 and it's serial # 2425. The next oldest I know of are serial 4703 and 5680. All are plain TS-4 chassis but none are dated unfortunately.

You can read more about it here: http://www.videokarma.org/showthread.php?t=251610

[Zenith26kc20]

one thing these little TV's can give is hours of reading and comparing schematics. I've carried them to a few audio shows and the people always loved em (and the sci-fi movies playing on them)!
We even moved a big (50') Sharp LCD into the hall once to make room for the retro "home theater"! The hotel said yes, move it, and out it went!

[Zenith26kc20]

the recap is done, the filters were ESRed, formed up and leakage tested. This is the second little Moto that the electrolytics are fine. When I variaced it up I was greeted by a 1/2 inch long line jumping from top to bottom. Two hours later I traced it to a broken wire very well tucked under a terminal strip that it didn't even go to. It was from the vertical oscillator plate to the output.
Put the wire where it was supposed to go to, hooked the chassis back up and a picture!!! Noisey and neither centering control works, all other controls are touchy but it's eyes are open. For what was the second worse basket case in my closet, it has come a LONG way.
Pictures Monday AM!
This one even has the metal can ballast that still is good! (That's why the variac turn on).
The worst basket case I have a bakelite cabinet that someone modeling clayed the CRT into place. It's chassis is a real mess also!

[Zenith26kc20]

This weekend revealed a problem I have never seen before. The vertical centering control had gone down to 1 megohm. This disabled both horizontal and vertical centering! I pulled the leads loose connecting the two controls and ohmed them out, the vertical being low. I went so far as to pull the control to be sure it was down in value. It is still linear thru it's range and the tap is correct in being half (.5 meg) on each side of the control. I put some 1 meg fixed resistors in place of the control and the horizontal centering works great. I may try adding one 470k resistor in each leg of the control to bring it back to 2 megohms. If the centering is adjustable enough (right now, with the fixed resistors it's nealy perfect) I may just leave it like that.
Now the snowy picture has to be tackled!
Oh, that is my test 7 inch CRT. I am very careful with the 8 inch. That one came from the bakelite TS-18 that is really nasty. Someone put some green plastic to hold the CRT in place and it melted everywhere. It took me an hour to scrape the bell and face clean. It's a Philco tube and it is in great shape!

[Zenith26kc20]

Last night I reinstalled the vertical centering control with the added 470 k resistors and now all the centering problems are cured. The next thing was what appeared as a snowy picture. I went to check the 6AG5 and discovered a 6AU6 in it's place. My tube tester calls for a lock out on the 6AG5 pin two, no lockout on the 6AU6. Installing a 6AG5 gave me a picture better on this set than my other two! I'm still using the 7 inch tube but to say the least, spectacular!
Stabilizing the picture seems to be more related to the sweep tubes. Older types seem to drift more than newer. The vertical is dead stabile. The horizontal is to the point where it locks in about 25 seconds once raster appears and requires one adjustment in about 30 minutes.
Tonight starts the sound circuit repairs!
And more pictures!

[kx250rider]

The only thing I can immediately suggest for anyone on these, and all 7 & 8 inch electrostatic sets, is do NOT use ceramic disc caps for the high voltage and sweep HV section. It's tempting to use .001 and .0047 @ 6kv discs, as they're easier and cheaper to get, but they have a radical warmup change in value. Spend the money and get good tubular mylars, and that will resolve the height, width, centering, brightness, and blooming problems during warmup. I don't think it would do much to stabilize the oscillators (H & V) specifically, but by stabilizing the high voltage and sweep, there will by default be a stabilizing of the B+ by not loading and unloading the line, and thus some stabilizing of the whole TV.

Charles

[compucat]

The only stability issue I have ever had on mine is the vertical oscillator. I had not thought about the tubes causing this issue. Maybe I will try subbing the vertical oscillator tube in mine. These sets do produce a good useable picture when properly restored. I can watch mine for hours.

[bandersen]

I've found the 6SL7 tube is especially troublesome. I think Motorola really pushed them to the limit as I've seen arcing in and around that tube.