[Penthode]

I have been looking forward to the Christmas break to pick up on the CT100. The rest of the family have been sick (not me and my wife) so we have postponed family gatherings this year.

Have completed two run throughs of the IF/RF and Chroma Bandpass alignments and testing. Subsequent run throughs of the procedure yielded some improvements in an attempt to get better frequency responses. I had spent many hours on this starting in late fall bringing me to this culmination point.

To achieve a flat topped wide IF response is the challenge especially with a stagger tuned amplifier with 6 stages! The video IF alignment of the CT100 require you to first sweep the 6th IF to 2nd detector stage followed by the 1st IF stage on the tuner followed by the first 2nd IF stage (first stage on the main chassis. Then the 3rd, 4th and 5th stages are peak aligned to 44.9MHz, 42.9MHz and 41.3MHz respectively. The final overall sweep requires you to adjust the 3rd, 4th and 5th to achieve the full 4.1 MHz bandwidth flat topped response. I could not achieve the response without tweaking the other stages. I feel it important to restrict the final response tweak to the three stages so experimentation was required to understand and determine where the discrepancy occurs. I found the problem with too much gain around the video carrier (45.75MHz) by very slightly altering the 2nd IF tuning higher in frequency to bring the whole respnse in line.

The luminance channel response with all traps and the chroma channel bandpass responses fell niceling in line with the RCA documentation. I had problems however with the I and Q channel responses. Recall all of the white peaking coils were open and I could not repair them.

I managed to wind myself replacements which worked fairly well. Q Channel 6.7mH coil I altered from a ferrite core 33mH coil only to find the the Q response diminished sharply after 100kHz. I ended up winding about 500 turns of AWG44 wire on a 1.0 Megohm 1W brown resistor which gave me the correct 500kHz response.

The I channel with the coils I provided peaked too sharply at 1.0 MHz. I found an old NOS Meissner 1.0 mH coil shunted with a 10K resistor which yielded the response I desired.

A frequency sweep from the 1st Video amplifier input to the kinescope grids did produce the response published.