Hello

,
You might want to take a look at this -->
ftp://bama.sbc.edu/downloads/radiocit/rc314/ It's the user manual for RC314 tube tester. I think it's pretty much the same as your RC315.
I would also recommend anyone who has an interest in old equipments (i.e. oscillocope, counters, testers, etc.) to check this website out -->
http://bama.sbc.edu BAMA (Boat Anchor Manual Archive) is a great site. FULL of information. They also have schematic diagrams for tube Heathkit, EICO, TELEFUKEN, etc.
In the U.S. these old equipment are called Boat Anchor because they weigh a ton!! You can them for next to nothing.

I bought an older analog Textronix oscilloscope, HP frequency counter, EICO capcitor tester, etc. for peanuts.

My Textronix oscope was a military model and it's built

a tank.
Hope this helps!
Best,
ABMOGGY

Governments have a tendency not to solve problems, only to rearrange them.
RONALD REAGAN
"The point of living and of being an optimist, is to be foolish enough to believe the best is yet to come." - Peter Ustinov