I'm working on an RCA 28x5. The schematic shows tube markings as K K1 K2 SG H P DG D1 D2 etc. How do I know which letter corresponds to which pin number?

You might be able to do it by finding a componant, like a resistor, and see what is attached to and counting clockwise from there. This may help, toohttp://tdsl.duncanamps.com/.

I just went to Nostalgia Air and looked at the schematic. If you look at the top of the tube symbols, you will see a little square. This is the keyway. Counting clockwise from the keyway is 1, 2, 3, and so on. Then you can get a tube manual online and confirm these results. So the first pin at the one-o-clock position is pin 1 of the tube.

Best Wishes,
nv3g
Oscar

Any radio I'm working on, I use a printed schematic, and if the
pin numbers are not already there, I mark them on the print.
Sometimes I even draw in the tube elements if they're not
already there and clear. Just simplifies work at the bench and
helps keep Murphy at bay.
Nelson

You can look up the tubes here:
http://frank.pocnet.net/

K K1 K2 SG H P DG D1 D2 etc.

The letters are abbreviations for the names of the tube elements.
K = cathode
K1, K2 = cathode 1 & 2 where there are two.
SG = screen grid
H = heater
P = plate
OG = oscillator grid
D1, D2 = diode plates
etc.

Note: the tube pin numbers are always counted clockwise when looking at the bottom of the tube or socket.

Yet another handy look-up: http://www.nj7p.info/Common/Tube/SQL/Tube.php

specifically what tube are you referring to

I think I better check them all. There are resistors and stuff that aren't shown on the schematic. It has been worked on before. (For example, there's a piggybacked capacitor that wouldn't have been original. The combined value is correct, though). Tube 1, calls for 6SG7, has been replaced with a 6SK7, The old plastic coated wiring is crumbling and needs replaced. In the schematic the H pins at the tubes don't show any connections; but that's because these pins are wired in series as shown at the bottom right in the schematic. Right? Assuming no other connections, is there an IN and OUT polarity on the H pins; or will it work either way?

Where the schematic shows H K G SG . . . markings instead of pin numbers, it doesn't necessarily mean that these markings are sequential corresponding to the pin numbers when viewed from the bottom of the set, does it?

By the way, I'm using 18 gua. braided copper wiring. Is that adequate? I assume, without a guage or anything, that a braided wire would need to be a wee bit larger in physical wire diameter to equal the guage of a solid wire.

A few of our older NMR's were made in Tokyo in a Hitachi plant in mid to late 1960's (Perkin Elmer R20A, etc.), where its transmitters and receiver chassis still had tubes, and its signal circuits contained early bipolar transistors. Not knowing Japanese, I always had to use translation charts to use their Japanese circuit diagrams and service manuals....it just took longer. Same with the German instruments in the department.....none of those diagrams or manuals ever were translated either. I've also seen Polish and Russian tube diagrams which also use their own labels, which just take a while to get used to. Also, Japanese-made VR tubes sometimes (but not always) have alternative labels, where an actual 0A2 may be an 0B2 or 0B3 etc., so one has to study the circuit a while before subbing for one of these older VR tubes; unfortunately, there wasn't a translation chart published for that. One advantage working at a college is that I don't have to go far (usually just another dept colleague or languages dept in the next building) to get these translations.