Motorola TS 18 horizontal issue
 

The original 7JP4 was gone, National Union (NU) made 8BP4 was found and it makes a decent but somewhat dim raster, there is no ion trap on electrostatic tubes, hence they test ok but dim due to phosphor degradation. Sound and video stages are OK. Vertical sync is OK, sweep size ok.

Current Problem: Horizontal too touchy, was able to get it "locked in" with a wiggle in the picture, now the width is decreasing and it won't lock then "xmas trees" out. The Sync clipper, AFC and Horizontal osc is two 12SN7s and two "blocking" interstage transformers and wonder if something besides tubes and capacitors*. Need to check voltages but was there an "old" thread on these?:scratch2:


*I recapped the chassis and rebuilt the ballast using sand blocks and ceramic log power resistors and diodes similar to Bob Anderson's thread, so no issues there and supply is B++ is 270v. I had three other JFD nib ballast replacements that also had corroded rivets on the "mica toaster panel", were thus useless:sigh:

Have you checked the high meg resistors in the horizontal circuits?

jr

Its going that direction, after all the cap replacement. I had checked most of them when I was on the focus issue. The blocking and coupling transformers seem to have continuity, which is a common fail in the older sets. Th HV itself measures about 5 kV

Im using the factory schematic form a Wallace Telaide, do not have the Sams set. Some of the voltages on both 12SN7s shown are measured from B+ instead of B- or chassis ground, which do not seem to agree with the values posted.

https://www.earlytelevision.org/pdf/motorola_ts18a.pdf

https://www.earlytelevision.org/pdf/..._sams_83-6.pdf

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Did you change the micas in the horizontal? They can drift and leak in the sweep system.

Thanks!

The 20 mmf and 900 mmf are prime suspects, plate circuit of oscillator V13.

Symptoms remain foldover on right side, lack of width and loses H sync. So few components but all that left is two transformers. T2-T3 on Sams schematic. T5-T6 on Motorola schematic

After replacing each of the mica caps 20, 200, 680 and 900 pf no improvement was noted. The resistors all checked - except one a bit higher than 10% - no change.

The negative voltage on grid of horiz osc supposed to be 50 but reads much higher, like 130! I tried freeze spray on both transformers after it fails, no change.

This is how it looks as it fails, image gets more lines, loses sync finally shrinks horizontally into a line

Another observation:

Horizontal size control is reduced, picture stabilizes although its only 3 inches wide. The interfering horizontal lines disappear, and a sharp bright and clear picture is seen, playing for 15 minutes this way. But, if the size control is set to max, lines get worse, H sync is lost and raster eventually collapses into vertical line. Something crapping out here, freeze spray no effect?

The right side of the picture appears to end in a bright line, similar to a vertical foldover. Vertical is functioning 100% with good linearity and size.

These are so similar to a TS4, would the transformers T2/T3 be the same?

Never mind, the 12SN7 was the issue. I'm not used to tubes being bad, trying to look past something so simple, a recovering tube-jockey.

Not done yet, the vertical began to act up. If signal is removed off-channel, the raster collapses to a horizontal line.

Vertical hold is good but at end of range, then begins to roll upward. As size is reduced, hold locks in again. All caps have been changed...resistors?