Sparton 16A211 Width Problem

[earlyfilm]

Originally Posted by Steve McVoy

I've been trying to find a width problem with this set with no luck. It lacks about an inch on each side. Width and Hor. Linearity work properly. I've checked all the tubes (by substitution) and all caps are new.

I have the proper waveforms and p-p voltages at W17 and W18 (see the schematic). Power supply busses are within 5 volts. On the 6BG6s, screen voltage is right, but the cathode voltage is 12 vs 18 on the schematic. Grid voltage is -25, but I noticed that setting of the hor. drive changes it from about -15 to -30. I can just barely get 20 kv on the CRT with the HV control full up. Boost is 550 vs 620 on the schematic. Damper plate voltage is right.

I have checked all the resistors and capacitors in the H. out, flyback and damper areas. I've even changed the yoke.

. . . . . Schematic is here (better to download the pdf so you can zoom in):

Steve,

I assume that you have done all these, sometimes, fresh eyes looking at a circuit might spot a possibility. From a schematic analysis, here are some simple checks that could have been easily overlooked:

Is the optional R158 which is parallel with R157 present? (This circuit should be either a single or a pair of resistors. The set should have either two 11000 ohm two watt resistors in parallel or one 5600 ohm five watt resistor. (It us easy to misread the schematic here if one missed the check-parts-list symbol! These resistors provide screen voltage for the 6BG6's.)

Check R178 for value. It is off the high side of the R-G-B balance controls. (It is not shown on your schematic, so I've added a complete schematic to this post.)

If your CRT is weak, has someone set the R-G-B balance controls excessively high to compensate? Are the three .022 caps off the wipers of R-G-B balance controls leaking?

Since a prior owner had extensively worked on the set:
Is the yoke a Sparton XD-2071-J or RCA 223D1?
Is the flyback Sparton XD-2166-J or RCA 240 T1?
Since that flyback has so many unused terminals and may be a replacement, did you check to see of the correct terminals were used?

Have you verified that the voltage on the on the HV regulator grid is within the specified range?

Verify the replacement component values and wiring connections of all the work done by the former owner of the set, preferably by someone who has not previously worked on this set.

James.