South of B'more, We got about 1/2 to 1-1/2" Nothing to worry about if you grew up driving in the stuff (Montana). But the Rednecks and the Soccer-moms are out there doing 60+ in 4WD sideways panic'ed at why it got that way. Physic's is Physic's, no matter whether you have a '63 bug with racing stripes or a F-350 Dually quad-cab, or a Jeep Wrangler.
Visualize a clock. The gap on a small signal tube (7 or 9 pin) is usually next to one of the rivets. Looking at the socket from the bottom of the unit, there is a space between pins 1 and 7(or 9). Pin #1 is on the left of the Rivet. But flip it over and pin one is now on the Right side of the GAP. Look at the pins on the tube See the Gap between pin 1 and pin 7(or9)? This way the tube can only go in ONE WAY. The LARGE 7868 9 pin novar or NOVAL(I can't remember which is which anymore) is a larger version of the small signal tube sockets. Tubes that have an OCTAL BASE (the Bakelite bottom with real thick pins) have a locator pin in the center. It's keyed for ONE WAY. If the locator KEY is BROKE off, you can get an adapter that fits over the pins and restores the Keyway. Fortunately there are NO OCTALS on the 400.
Seeing as this is going off topic, I recommend that this be moved to a separate thread. This will give you an individual thread for the 400, and make it easier to find, plus it allows the topic here to continue. Go ahead and start the thread and I'll ask the Moderator to cut and paste over to the new thread, from post #37 to this one.
I made up a drawing of a 9 pin socket looking at it from the bottom. The 7 pin socket is the same just less pins. And the output tubes are the same on this receiver. Determine where pin 1 on all the tubes and mark next to the socket pin 1. You can do the same with a marker on the TOP. Alcohol will dissolve the mark when you're done. Use a cotton ball and 91% alcohol to remove it.
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