Rare Hallicrafters CTC4 clone resurrected from the dead.

[jeyurkon]

I think that would be difficult to answer unless someone was involved back then.

I'd guess that seleniums were still viewed as reliable. You wouldn't have to deal with the 3 amps needed by the 5U4 heaters, seleniums take up less space and run cooler.

I think the space issue was why the Sylvania 1-128 used selenium rectifiers in addition to a 5U4 and 7X6.

John

Originally Posted by ohohyodafarted

Just out of curiosity does anyone have any insite as to why RCA used selenium stacks in the CT100 thru CTC4 series instead of 5U4s?

Starting with the CTC5 and going forward, RCA switched to using 5U4s.

Data sheet for 5U4 indicates it will produce 225ma of dc current. I don't know what the ratings of the selenium stacks are, but my measurements indicate that a pair of 5U5s in parallel would be enough to supply the 440ma I measured in my CTC4. And further, the B+ fuse in the set is 450ma.

Here is a link to the technical data for an RCA 5U4. I must confess I'm not much good at interpriting these graphs.

http://www.mif.pg.gda.pl/homepages/f...49/5/5U4GB.pdf

Do you think this was an issue of reliability/pushing 5U4s to their upper limit, or cost in manufacturing considerations?