"The All Japanese 6" Receiver

One of the great things about having a "miscellaneous" box in an otherwise well-ordered junk collection is that rummaging through that box will often send you off on fun and interesting radio adventures.  I was rummaging yesterday and I came across the guts of the little AM radio that used to be mounted on my bicycle handle bars.  I last mentioned this in 2011 : 

http://soldersmoke.blogspot.com/2011/08/bike-radio.html

I was just about to cannibalize this board.  The IF transformers were almost certainly at 455 kc and I could use a few of those.  But then I started thinking and Googling and trying to figure out the circuit.  That all led me this the site that provided the diagram below: 

http://www.angelfire.com/planet/funwithtransistors/Book_TS_CHAP-7.html

Six transistors, four transformer cans, two audio transformers.  Yea, that's pretty close to what I was seeing on my board.  So of course I had to see if I could get it going.   I hooked up a 9V battery.  I connected the pot wiper connection directly to the connection at the top of where the pot had been (it had disintegrated).  It works!  It is inhaling nearby WFAX, Falls Church, Virginia. 

You will notice that the transistors in the circuit above are PNP.  I had assumed negative ground and had hooked the battery up accordingly.  No smoke was released and the thing worked, so I guessed that I had assumed NPN correctly.  Sure enough, perhaps aware of the PNP ancestry, the manufacturer had marked my board "BC123 NPN"! 

The author of the book I linked to above dubbed this circuit the "All Japanese 6"  -- an obvious allusion to the All American 5.  

I see real potential in these AJ6s.   A few mods to the front end and you could be shortwave listening, perhaps on 31 meters!   

BTW:  The space on my handlebars formerly occupied by that little AM radio is now taken up by a Bluetooth speaker that plays tunes streamed to my I-phone from Pandora as I make my way down the same old Washington and Old Dominion bike path.  Progress. 

Mr. Carlson Restores an All-American Five -- Tribal Knowledge! SITS! Flattening the Curve! (video)

It is always a pleasure to see a new video on Mr. Carlson's awesome YouTube channel, especially in these days of Staying-In-The-Shack (SITS).  Obviously Mr. Carlson is doing his bit in this area.  FLATTEN THE CURVE!   Thanks OM! 

My recent bout of S-38E madness has peaked my interest in the All American Five design, so this March 10, 2020 video was especially interesting to me.  Mr. Carlson puts out so much great tribal knowledge.  I didn't know about "rounder" resistors.  I didn't know that you have to be careful not to short out (to the IF can case!) the 455 kc transformers.  I really like his approach to dial cord restoration.  

Mr. Carlson's discussion of the adjustment of the front end tuner circuit on this broadcast band radio was very interesting.  Unlike the S-38 radios, there are no front end coils being switched in as you change bands. In fact, it appears that that big coil/antenna inside the back cardboard piece IS the front end coil.  This discussion has caused me to question my front end alignment technique for the S-38E.  Did I have an appropriate antenna or antenna substitute across the antenna terminal when I set the peak on the input LC circuit?   I will check on this.  Hooray!  One more thing to do during the COVID-19 SITS period.  

UPDATE:  I checked on this using the test set up described in an earlier post, but this time with my antennas connected.  First with a 40 meter dipole, then with my 130 foot doublet, then with a 50 ohm dummy load I was still able to see the resonance dips at exactly where I wanted them to be. 

My favorite bit of Carlsonian wisdom from this video?  Mr. C's confirmation that some hum in All American Five receivers IS NORMAL!  (This may be too much for the folks who find normal band noise to be offensive.)