CTC5 Video Response

[Penthode]

Originally Posted by old_tv_nut

The CTC5 super chassis can fairly be described as a collection of failed experiments in cost reduction, IMO. Video, sync, chroma, and audio all have minimal performance.

I can understand your disappointment with the Super chassis. My set currently has relatively poor vertical sync and poor luma resolution despite changing all the paper caps and IF/RF realignment.

I was was somewhat taken back that there is no 4.5MHz trap in the luma path, unlike the CTC7 onwards. Certainly the CTC4 and CTC5 were evolutionary designs in cost cutting. I have yet to sweep the video amplifier and shall be looking for drifted resistors and bad peaking coils.

I have noticed however that the Deluxe CTC5 has two Snd. IF traps instead of the one on later chassis'. A 4.5MHz trap is in the chroma path only. Perhaps it was felt that the two Snd. IF traps were sufficient with a narrow video amplifier response?

I have compared CTC5 with the CTC7 thru CTC10 video amplifiers and they are suprisingly similar. I recall the CTC10 I once had delivered a sharp picture. But that was within the context of thirty years ago and my memory may be faulty as I am exposed to HD displays today. But I can say that a direct comparison of the CTC5 picture on my 1949 Black and White RCA with a 16AP4, the old 1949 set delivers a nice crisp picture and the CTC5 can't compare.

I am suspicious of the encapsulated coating on the peaking coils and of drifted resistors. I have noticed that the 180uH peaking coil feeding the grid if the video output in the CTC5 has an 8.2 kohm resistor shunt whereas the CTC10 has the same 180uH peaking coil at the video output grid with a shunt of 39 kohm.

I shall make some minor modifications to the video amplifier and shall perform some sweep measurements to see if I can improve the high frequency response a bit.

[teevee]

Perhaps these notes ref the CTC12 will also apply... (From a Jack Darr book)

[NewVista]

Originally Posted by Penthode

I have compared CTC5 with the CTC7 thru CTC10 video amplifiers and they are suprisingly similar.

Of course it could be accomplished with 1/3 the parts like they did at Admiral

[David Roper]

But did you notice that one version of that chassis drives a four-speaker sound system with a 6L6? Must be the huge Patrician model, the one that resembles a stereo combo. Sorry for the hijack, but are any of those known to exist?

[NewVista]

Originally Posted by David Roper

a four-speaker sound system with a 6L6?

Their audio is nice design also: simple bass+treble controls + neat feedback Presence control

[Penthode]

Originally Posted by teevee

Perhaps these notes ref the CTC12 will also apply... (From a Jack Darr book)

This is very interesting. The RCA Service folk recognized the same problem? And then suggested tilting the IF to boost the higher baseband video frequencies!

Hmmm...I am going to see if the problem in the video amplifier can be minimized...