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systems_glitch

Western Electric J94071B Milliwatt Reference Generator

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I picked this up in a heap of old computer, radio, and telephone equipment, from a guy who had been an engineer in the Navy, then an engineer/lineman/programmer at Bell Labs in NJ:

 

sEcpz65h.jpg

 

It's an *actual* milliwatt! I can't find the BSP for it online, but I did find a hardcopy on eBay, so I'll scan that in when I get it.

 

jdXJgkUh.jpg

 

Battery test points, this is the battery (well, the top of an old one):

 

POV8ZtTh.jpg

 

45V "B batteries" were common in old radios and other higher-than-we're-used-to voltages were common in other types of test gear. For instance, a kick meter uses a different 45V battery (looks like a giant 9V and is still made).

 

Top of the internal circuit subassembly, the battery goes in the space seen at the top of the picture:

 

WbJv6fOh.jpg

 

Here's the circuit:

 

LOkkrMJh.jpg

 

Typical Western Electric, potted networks, switchboard jacks, and expensive resistors and capacitors. Not yet sure if the pot varies pitch or level. You can see there's a single very old GE transistor in a metal can package clipped to the side of the uppermost (4002A) network, presumably the only active component in the circuit.

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nice! do you need the schematic? i might have a copy.

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The copy of the BSP I ordered should have the schematic in it, I'm guessing it's nearly the same as the 71A (which I did find) except for battery power instead of DC plant power. I will definitely take you up on that offer, if the BSP doesn't include it!

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I have one of these too.  I thought I had the documentation but I can't locate it.  Works like a champ.  Mine was similarly clean inside - that cover really does its job.

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