Next NMRCC meeting: Atwater Kent tube radio sets

1 # 01 2016 Vol-22 Next NMRCC meeting: January 10th 2016 Atwater kent tube radio sets Sparton radios were not you usual run of the mill sets , they were high quality in every respect. The late 20's models were unique in several ways, not wanting to be a slave to RCA, they had their own line of vacuum tubes that did not require the RCA license. Most significant was the unique tuning circuit as used in the above and other "Equasonne" models. 1929 Sparton Equasonne Model 301 by Richard Majestic T his 1929 latest Sparton model is similar to its predecessors except for a few refinements in coil construction.

2 The receiver consists of three separate chassis one containing the audio power amplifier and pow-er supply. Six Cardon 484 heater type tubes are employed in the RF and detector circuits, two '50s (now 2-2A3s) in push-pull in the audio power output stage and two '81 rectifiers for B+ power. All tuning is accomplished in the selector unit which precedes the first RF amplifier tube. This unit consists of four tuned circuits and is controlled by a four-gang variable capacitor and an antenna trimmer. The four circuits are inductively coupled by a small section of the third winding, thus operating on the theory of the band pass filter selector.

3 Trimmers are lo-cated on each section of the tuning capacitor gang and each circuit is properly balanced be-fore leaving the factory by bending the rotor plates. The RF amplifier unit is untuned, right to the detector. The full responsibility for selectivity depends upon the band pass tuning selector, allowing the amplifier to be operated so that maximum gain may be obtained without affect-ing the frequency of the selected signal. The idea is not new but is very interesting in the way it has been worked out. All RF amplifier stages are coupled by RF chokes, as shown in the circuit diagram.

4 The "feeder" choke in the plate circuit of the first tube is wound single with a reversal of direc-tion in the middle, and a resistor is included in series with it in order to equalize the reactance of the parallel winding. The latter is the prima-ry of another choke, which is wound like a (Continued on page Four) 1 9 5 7 E m e r s o n m o d e l 1 2 3 2 t e l e v i s i o n b y J o h n E s t o c k At the June meeting I was fortunate enough to be the sole bidder on a cute little piece of elec-tronics, this time an Emerson 1232 TV, from 1957. Except for missing telescoping antennas, 1 knob and handle, it appeared to be complete.

5 Lars walked away with the astronomical fee of one dollar. The first step in vintage TV restoration is testing the CRT; if bad, you either have a box of (Continued on page Five) 2A3 Two The NMRCC Meeting Minutes by John Hannahs John Secretary Richard Majestic. Director Ron Director Ray Director John Director notes; Lynn Toppo will assist Mark with his duties. Chuck Burch will normally serve as as Auctioneer and Richard Majestic will publish the NMRCC Newslet-ter on a discretionary basis. Your ratification of the above and com-ments regarding alternatives is essential for the best perfor-mance this coming year.

6 We've come a long way. The occasional "Guess What" club exercise consists of mem-bers bringing some obscure de-vice to the table for identification. Chuck Burch brought a precision casting with a central coil of wire that moved left and right on a bearing surface. It was all very precision and looked like it was quite expensive to manufacture. Turns out it is the actuator mech-anism from a DEC RA60 hard drive, circa 1983. It is basically a "speaker coil" that moves the read/write heads laterally across five stacked and rotating data discs. The platter is removable.

7 I should have known this, as I did work for the company for13 years. Duhh! I brought what ap-peared to be a gold plated tran-sistor with a clear window. It was owned by a scientist named Op-penheimer at the Labs ( not the crusty J. Robert one, but still re-lated to the father of the A bomb). I knew it had to be more than just a photo cell. According to John Anthes it was actually a quadrature detector that could sense light coming from a direc-tional source. I thought that was pretty exotic, but Chuck won. Anyway, mark your calendar 1 pm, January 10, NMRCC . Consider bringing a guest who has an interest in yesterdays radi-os and electronic equipment.

8 Happy Holidays, John Hannahs NMRCC 2016 MEETINGS JAN 2016 - Atwater kent tube radio sets FEB - Homebuilt crystal, tube, and transistor sets MAR - Mirror radios, all years APR - Test equipment and classroom demon-stration equipment- tube testers, signal genera-tors, oscilloscopes, bridges, meters and etc MAY - Spring Picnic JUN - Television sets , 1946 through 1970 (anything you can carry into the conference room) JUL - Early TV cameras, camera tubes and CRTs AUG - Foreign Radios SEP - Field day/ radio reception contests OCT - Fall picnic, ribeye steaks Las Cruces NOV - Wild Card Sunday (nifty science giz-mos, novel science toys, or non- radio collec-tion, electronics, or science related that you think will dazzle your fellow members DEC - Holiday party theme: Little-known radio man-ufacturer and rare radios Subject: December NMRCC It's 1 pm Sunday the 13th and every-one is already present at Mark and Lynn Toppo's home, Radioland USA.)

9 The contingent from LasCruces all came. The house was full of members and sig others. Food and goodies were everywhere, including liquid libation. Now I am a museum going freak; been to science museums all over the US, Paris, Munich, London, and so on. No-body does radios from the 20's into the 50's better than the Toppo's. None are so gracefully restored, cate-gorized, and displayed. The junkers are hidden somewhere in the garage. Some members, like Richard, help Mark with the electronics. I get excited looking at those magnificent chrome plated Scott chassis and the fine wood restoration, some looking new, except they may have been a former basket case.

10 For certain some were formerly infested with fly specs, spider webs, and even worse. Usually capacitors and flakey components have been re-placed and a total re-alignment has been done. Not always, but rest assure Mark will disclose the condition. He seems to remember all of the details regarding each unit. So, another great year is shot. We had no great presentations at this meeting, just a great social get-together where members could ask each other ques-tions like "how does a grid-leak capaci-tor work, or how can I go about re-winding this power transformer, or who re-cones old speakers.