This Type 3A74 Vertical plug-in came with the junker Type 561B that I got from Nixiefreqq last week. Unlike the mainframe and the Type 3B4 Time Base plug-in it appears to be in decent shape with little or no moisture damage and no mold. So I'm going to try to get it running.
It is a 4 channel plug-in with a 2MHz B/W. A view of the component side shows that this unit is packed real tight.
The opposite side and the vast amount of compensation trimmer caps for each channel. All that metal shielding results in a plug-in that is surprisingly heavy. And 8 – 7586 Nuvistors. But there is something strange with them. They are stamped “Japan” and a maker's mark that looks like a miniature life preserver or possibly represents a globe of the world. It's hard to tell. Now I thought all nuvistors were made by RCA so I did some research. Yes, RCA designed and introduced nuvistors in 1959. Later they were also made by GE, Raytheon, and Philips. There are also nuvistors stamped with Mullard but they were actually made by Philips. I could find no information about them being made in Japan but I have proof in front of me that they were.
So who made them? I have a couple of ideas. The first is Matsushita (Panasonic). They made standard 7 and 9 pin vacuum tubes. I recall working on a Panasonic TV that had Panasonic branded tubes. And it even had a unique one that wasn't in the RCA Receiving Tube Manual. So it wouldn't be a stretch that they made nuvistors. The other possibility is Toshiba. I don't know if Toshiba made standard vacuum tubes but I do know they made CRT's. My B&K 2120 scope has a CRT made by Toshiba. So that's my suspicions but of course I could be totally wrong. And I really don't think Sony had any involvement.
I'm going to deoxit the switches/pots and do some resistance checks for shorts and plug it in and see what happens. But that's later and I'll post the results. Stay tuned.
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