I recently bought a 3B3 via ebay, that I got cheap because it had been damaged. The only obvious damage was that one of the long, round, chrome plated chassis rods was badly bent. I thought I had some good, salvaged, 3-series rods so I figured this might be an easy fix.
First surprise: I don't find any chassis rods in my stash of Tek spares. I managed to straighten this one. It's not bad, but if someone has a good one they'd like to part with, I'll pay a reasonable price for one. Note that the 3-series chassis spacing rods are ~12-3/16" long, longer than the 1 or Letter series rods. This is a late rod, with the crimped hex at one end.
Second surprise: One of the 6DJ8s has the getter turned completely white. It had been knocked sideways by whatever had bent the rod, so I figured there must be a crack around one of the base pins, which had been bent. No such cracks appeared, but I finally noticed that the pinch tip at the top of the tube had been completely broken off. Sad, but at least I have a few spare 6DJ8s.
However, this dead 6DJ8 is unusual. There is no etched ID anywhere. In typical red ink, it says NATIONAL, with the National logo, then the Tek part number, 157-0125-00, then MADE IN JAPAN. Oddly, 6DJ8 does not appear anywhere.
The 157-0125-00 is an aged and selected version of the 6DJ8. So, with the Tek part number inked onto the glass envelop, the ageing and selecting must have been done in Japan, by the original manufacturer. Or perhaps they were able to control their production carefully enough to make the ageing and selecting unnecessary. I'd love to know how this was done.
Or maybe this was done so late in Tek history that no one cared. There are some additional numbers in red ink on the tube: 51A, 83781, and 8729. The last one might be a date code.
So, at some point in time (1987?) Tek contracted with Richardson Electronics, in the Chicago area, to make 157-0125-00s (6DJ8s) for them, with the National label on them. Then Richardson turned around and subcontracted them to Japan (Toshiba, Matsushita, Hitachi?) to make the actual tube. I have to assume that this was all done with Tek's approval, but it still seems odd, especially with no 6DJ8 marking. This was probably a very nice tube, and probably still is, except for being full of air and the consequently blown getter.
Have you ever seen a National, or any other brand, tube with the 9 digit Tek part number printed right on it?
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Jim Adney
Madison, WI USA
