Replace four paper capacitors with modern equivalents
With an external power supply connected to the "+400V" point on this schematic AND to the 68K 1/2-watt resistor [2R267 RCA; R174 Sams] on terminal "D" of the horizontal sweep oscillator transformer (that 'floating' resistor shown on the schematic), you can check for the waveform below [Sams W16]. You may be able to vary the period -- use the horizontal hold control -- around the 63-microsecond horizontal line period. If not, the slug on top of the horizontal sweep oscillator transformer may require adjustment.
NOTE: Isolate the 6SN7 circuit from the rest of the CTC-2 chassis for the above test as follows: Disconnect both resistors from the B+ bus before applying power to this circuit. (a.) 56K 1R294 is located above the chassis behind the horizontal hold pot. (b.) The hot end of 2R267 is easily lifted from its tie point underneath the chassis.
The ballast assembly that plugs into a socket on the back of the rectifier cage should NOT be installed.
------------------ At terminal "C" of 2T119, the horizontal sweep oscillator transformer, you will see [Sams W15] a characteristic SynchroLock waveform "Combined grid voltage" as illustrated in this 1954 graphic from a Grob color TV textbook. ------------------
