CTC-4 Director 21

[bigaudioal]

Originally Posted by miniman82

The problem is not the literature for the chassis, it's the specification itself. Not only did they choose an anode supply for the 5 chassis which only provides around 20kv to the CRT, they also for some unknown reason decided to not make up for that lack of voltage by having ample current reserves. To understand why this is a detriment, see note 3 of this PDF on the 21AXP22:

https://frank.pocnet.net/sheets/137/2/21AXP22.pdf )

I say lack of voltage because the 5 is the only one that low, all other chassis (especially the earlier ones) made a full 25kv and had more than enough current in the anode supply to make a full and bright picture without trying very hard. Add this to the fact that the data sheet on the CRT even tells the engineers that less anode voltage equals less brightness, and it will always be a mystery to me why RCA chose in this one particular chassis to do what they did. I don't care to speculate why it happened, it's an issue and makes the 5 a real dog in the brightness department compared to other sets.

Ah, I see. So it was the design of the set which produces the lower HV, thus being the least adequate to run the AXP. So the set literature is accurate and the 20kV is "normal" for a CTC-5. But that is barely enough to produce a decent picture compared to other sets of the same time period which produced around 25kV.

Very strange they did that considering the specs and notes on the CRT they were using.