Atwater Kent Receiver 20 C

This Atwater Kent Three Dialer receiver has chassis number 247450. It is a 5 tube model, build in 1925. This one belongs to the 7570 series, and therefore to the 1st of the 2 series of model 20 Compact. It was sold in 1925 for  $ 80, while the 2nd series was priced in 1926 with $ 60. The AK 20 series 7570, a 5 tube type 201A receiver, is using 3 different B+ voltages: 22V for the detector 67.5V for the RF amplifiers 90V for the AF amplifiers Grid voltage is -4.5V, heaters are 6V brutto or 5V netto. I've found an excellent webpage with a lot of documents for the AK model 20: Jim McKinnon's AK 20 Page I had to replace 2 resistors and 1 cap, then my AK20 set was ready to run. Faulty resistors was one of the 600R coil  resistors and the 2M grid leak resistor. I opened the large 0.2µF cap and placed a small 0.33µF MKT cap in it. The mahogany cabinet and the chassis are in really good condition, so I just polished it.  From the batterie cable just a very short piece was remaining, so I had a look around and found very nice 8-wire cable with brown cloth cover at Antique Eletcronic Supply (AES). I got 7 feet of it to use one half for the Atwater Kent and the other half for my Freed-Eisemann NR-7 receiver. This is the schematic of the Atwater Kent model 20 series 7570 receiver: AK20 schematic   To fire the receiver I'm using my DIY Power Supply. Connected to my E-3 speaker the set works very well. The AK20 chassis equipped with 5 tubes type 201A Talking about the tubes: often the old 201A or 301A tubes appear to have open filaments. But in some cases the filament is not broken, it has just no connection to the socket's prongs. You can try to resolder it; sometimes it works, sometimes not. Having 5 of this dull 201A and 301 tubes in front of me I thought about to give them a last try. I de-soldered the prongs, did the tubes into the oven on 150 degrees C. On this temperature it is easy to separate socket and bulb. Then I've connected the multimeter directly to the wires coming out of the bulb. Result: 3 of the tubes were indicating resistance: 6 ohms, 17 ohms, 20 ohms. All right, I took the tubes on the tube tester. The 6 ohms tubes was gone in a few seconds, must be a short in it. The next tube worked, but with a short between grid and filament. But the third tube was fine: reading a value of about 26 on the TV-7, where 18 is the mininum for a 01A. A 301A bulb tested on the TV-7 I soldered thin long wires to the originaI wires, and then the wires with fresh solder to the prongs. I used filling compound for wood as a cement to rebase the bulb in the socket. Great, a Cunningham C-301A was ready for going back to service!

Atwater Kent Speaker E-3

This is an Atwater Kent E-3 speaker, series number 476703. E3 speakers were build starting 1927 with the first AC receivers of Atwater Kent. The E-3 speaker is a full floating speaker, high impedance speaker. DC-R is about 650 ohm, so it is usable with the transformerless battery receivers like the model 20. Condition of the E-3 speaker is excellent. A new painting in brown and gold, and the speaker was ready to rock.

Atwater Kent Speaker F-4
 

An Atwater Kent F-4 speaker, series number 1210837. It must be build about 1930. Originally it was used with the Atwater Kent model 55, an AC powered receiver. Atwater Kent has build a range of electro-dynamic (field coil) speakers in the late 20ies, shown in an old Ad: Impedance of the F-4 Speaker is 8 ohm, so it was build to be used with a receiver which has an output transformer. Also it needs a DC supply voltage, because it is electro-dynamic. I did some tests with a solid state power supply and got this results: on 230V AC input the speaker consumes 90mA at 220V DC on 105V AC input the speaker consumes 40mA at 110V DC I had to do some restauration on the speaker, because the paper ring holding the cone was totally destroyed. I used 200 gr/m2 paper to build a new ring holding the cone. Works pretty well. This was how the cone looked before I started to fix it: The cone is clued and fixed: The back side of the speaker: Restauration finished: Atwater Kent F-4 Speaker: The solid state Power Supply is very simple, just using 1 diode, 2 caps and 1 resistor: F-Speaker PS I decided to go for 115V AC input to lower the power consumption and possible stress for the speaker. From a small wooden case I builded an adapter box for the speaker, with a small power supply for the supply voltage, and with an output transformer  2k DC-R pri to 4R or 6R sec. This adapter makes it possible to use the F-4 speaker with the old transformerless battery receivers too. From 115VAC input 125VDC are deriving. An old phenol UX4 socket was modified to accept the original 4 prong speaker connector from Atwater Kent.

Back to my Antique Tube Radio page

Last update: 29/April/2004