Videokarma.org TV - Video - Vintage Television & Radio Forums

- Early B&W and Projection TV (http://www.videokarma.org/forumdisplay.php?f=19)

- - Working on a RCA KCS72M (http://www.videokarma.org/showthread.php?t=260324)

Quote:

Originally Posted by bandersen (Post 3090988)

Quite often there is a mica cap inside the yoke across the horizontal coils. This set has a 91pF in series with a 1,000 ohm resistor.

Here's the schematic from Riders vol 10. There are several chassis revisions and this is the earliest. http://www.flickr.com/photos/70039806@N00/11598231834/

There's a bit of difference between the KCS72 and the KCS66, schematic as shown.
The KCS72 must be the el-cheapo model, that year.
I have two 21" consoles with that chassis. It uses the older type penthode tuner and a 21mhz IF strip, which was strange, as RCA was one of the firms, that changed to 41mhz IF's early on.
The KCS72 chassis used a 5U4 and 5Y3 rectifier, power supply, where the KCS66, used a selenium rectifier and voltage doubler power supply.
The KCS66 uses a 41mhz IF and a cascade tuner, plus four stages of IF.
The horizontal sweep should be very similar. Yoke is the same.
Spellcheck didn't like the tuner description, regarding the RF stage. :boring:

Oops, I uploaded the wrong page :o Check that link again and you'll see the KCS72M2 late schematic. It uses a 21MHz IF.

Quote:

Originally Posted by bandersen (Post 3091185)

Oops, I uploaded the wrong page :o Check that link again and you'll see the KCS72M2 late schematic. It uses a 21MHz IF.

PICKY, PICKY, aren't I! :D

Quote:

Originally Posted by bandersen (Post 3091185)

Oops, I uploaded the wrong page :o Check that link again and you'll see the KCS72M2 late schematic. It uses a 21MHz IF.

PICKY, PICKY, aren't I! :D

Well I've made some progress.

Some time ago I tried the set with an external HV supply I made for another purpose. During and after that I the original yoke confirmed it's defectiveness by smoking a bit and heating up.

Today I made a significant step towards getting it working. I parted out a 17" split chassis Philco set whose cabinet was a bit too rough to be worth the effort to deal with. In addition to many good parts the set had what appears to be the same CRT as my RCA and the Philco jug tests MUCH better than the dying RCA CRT. The Philco yoke also seems to work okay in the RCA so I'm going to use those parts to get the RCA going.

Some time in the next few weeks I should be able put together in enough 'a couple of minutes here and there' work to get it running properly.