The Hamfest Herring Aid 5
For background on all this, see yesterday's blog post: https://soldersmoke.blogspot.com/2023/10/a-big-error-discovered-in-1976-qst.html
Rick WD5L noted that it was remarkable how the builder of the Herring Aid 5 that I found early in 2023 at a hamfest had built his receiver using MPF102s at Q1 and Q5. Here is how this builder kind of "shoe horned" MPF 102s into the QST Herring Aid 5 boards. Pinouts for the MPF102 and the RS 2035 and the PC Board Pattern for the Herring Aid 5 appear below.
Above is Q5 the VFO. You can see how he "flipped it around" to get the Drain, Gate, and source in the proper holes. You can also see how he wound the transformer for the VFO. Looks like there was a real battle with the soldering iron here.
Above is Q1 (RF amp). Again clearly an MPF 102. But here it would not be sufficient to just flip the transistor around. So he had to twist it and take the center lead and put it in the far right hole. Note his markings on the board. Looks like he made another hole for the MPF102 Gate (but he didn't really have to do this).
DOES ANYONE KNOW WHO BUILT THIS RECEIVER?
ARE THERE ANY OTHER HERRING AID 5s OUT THERE?
DSG
DGS!
Click on the images for better views.
Golly, as Gomer Pyle would say! Your Pinout D-S-G concurs with my 1970 Motorola Semiconductor Data Book. That could be a problem for a builder!
ReplyDeleteThe MPF102 & some other FETS like the 2N3819 are symmetrical nJFETs, so the the drain and source leads are interchangeable
ReplyDeleteThe problem is that the 2N3819 (RS 2035) has the Gate as the center lead. So at Q5, if you just soldered the transistor in, the way that the board was laid out would cause you to ground the gate. It would not oscillate. That is why so many of these receivers never worked.
ReplyDeleteTrue, there are some (not all) JFET's that have interchangeable Source/Drain leads. Depends on the manufacturer's process and die topo.
ReplyDeleteBill's note involved a part from Rad Shack with incorrect pinout- ouch!.
Was there a subsequent errata published in QST? I wonder if they addressed all the issues?
ReplyDeleteI was unable to find any errata using the search tool through past issues of QST at the ARRL website.
ReplyDelete