That unit was made under many brand names:
E.F Johnson...Lafayette Radio...Courier...Think maybe even Royce or Robyn/Allied Radio had a version...only think the name plate was changed...
It was fairly common in the early 1970's.
I sold quite a few at the shop till mid 70's, and recall the manual was maybe 4 pages.
One page was schematic and calibration info, another was safety info.
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I think it may have been made by Panasonic/Japan (or the contractor for them)
They also made the larger relabel versions of the of the tube radio...Comstat/Gemtronics/Robyn etc transceivers...
I know this helps ZERO but the manual for that tester may show up under many names, but it truly had very little in the way of diagnostic information included.
I realize this is a bit of a necro, but...
Gary, your post was immensely helpful! And the additional historical input is very helpful (*especially when it comes from first-hand sources who were there*, even IF the memory is a bit foggy at times! lol
Ask me how I know.)
The Courier Port-A-Lab 500D was made by Cybernet Electronics Corporation (as were many other brands.)
"Cybernet, for example, manufactures C.B.'s marketed in the United States under the labels of Lafayette Radio Electronics, RCA, General Electric, Midlands and Craco, along with more than a2dozen other brand names." - credit to a 1976 NY Times article (that AI pulled up on a Google search) *spelling issues left intact.
Courier, Kraco are obvious, and I *strongly believe* that Eico also belongs in that list: compare for example the Courier Port-A-Lab 500D (controls, layout, meter, and dummy load) to the Eico 715 Trans-Match!!
Been looking for a schematic and operation manual for the 715 for a while now, when I stumbled across the Port-A-Lab (which I was previously unfamiliar with). The idea instantly struck me that these two probably came out of the same factory when I saw the face, and then compared models of varying age. (Some Port-A-Labs have the RF connections on front, and others on back)
Anyways, just wanted to say thank you for your contribution to the thread. It still proved fruitful. (Hoping mine does similar for others)
Lastly, I'm still looking for a pdf manual for the Eico 715 if anyone has one! Would be all too happy to have the one for the Port-A-Lab though! As I can't imagine there'd be that many drastic differences between the two.
Best regards!