https://lh5.googleusercontent.com/-BmTLECH03Jg/VNvYkUekDuI/AAAAAAAANrE/pDC4GRxuaro/s640/AK%252030%2520800.jpg

I just finished the cosmetics and electronics on an Atwater Kent 30 (6-tube TRF, DC) chassis. I rebuilt the paper caps, replaced the grid leak resistor and one open resistor. Remaining components were close to the original values. After doing some alignment of the tuning condensers, the set had pretty good sensitivity but the volume was low and the quality of audio was poor. The best sound I could get was like this (30-second video):

https://picasaweb.google.com/lh/photo/MM70-hmVJmq_VBsFl1m9YtMTjNZETYmyPJy0liipFm0?feat=direct link

(If the video doesn't play, just forget it)

Following advice for restoration of the AK Model 40, I doubled the grid leak resistance and lowered the grid resistors by 100 ohms (500 down to 400). Will wonders never cease?...it worked! Great improvement in audio quality.

But, of course this leads to several puzzlements. First, on the zero-to-100 tuning dial, the frequencies are received in reverse of the convention order.

https://lh3.googleusercontent.com/-7RQHvwhCurU/VNvYktidbvI/AAAAAAAANrI/_Ei94ID195E/s288/AK%252030%2520760.JPG

Is this by design, or did someone make a mistake in assembling the center condenser? Looking at the picture below, I think that if the stopping arm on the condenser is repositioned 180 degrees, then the set could be realigned for reception in the conventional order. I wasn't able to loosen that nut easily, so I'll probably leave it as is.

https://lh3.googleusercontent.com/-1dkoGbk3sFY/VNvYjSCeBAI/AAAAAAAANq4/ODn4-GvQMnE/s400/AK%252030%2520780.JPG


The audio volume is still quite low. Sitting close to the speaker with maximum volume, only the strongest stations sound too loud. I've tried juggling RF and AF tubes; replacing the detector; and operating with both 90v and 135v plate voltage for the last AF tube, but that hasn't helped. Should I expect more volume?

https://lh5.googleusercontent.com/-NUW1hKiVCKw/VN2cUd3-FtI/AAAAAAAANss/9MQccUVH1AA/s800/AK%252030%2520762.jpg

Finally, I don't know what the detector rheostat is supposed to do. It's not even addressed in the instruction book! The RF rheostat control regulates the RF and detector filament voltagess from 2v to 5.6v. The detector rheostat does the same thing.

Did you check your audio transformers? IIRC, one set I have had the same problem. Audio transformers were open on one side. Did a fix by 2 resistors and a capacitor. I would have to dig out my notes to see what was done exactly.

Thanks. This was my data when I started the project, I verified it when I reassembled the chassis. I'll look at the AF transformers again for continuity and wiring errors, but they're probably not the culprits.

https://lh4.googleusercontent.com/-uJH6Hw8zs_s/VID07vwZ4aI/AAAAAAAANOw/5KKdrYLIidI/s340/AK%252030%2520610.jpg

what are you using for a speaker? Most of these ancient sets had the speaker connected directly to the output tube, you need a high impedance speaker, or add a matching transformer

Good thought, but I've been using a couple of balanced armature speakers that work well with two other TRF sets.

Incidentally, the AF transformers' resistance checks out OK. I noticed that the data in the above schematic are different, but mine match up with AK's published values.

Thanks.

And the answer is: I had the 1st AF miswired to the power supply, hence no B+ to that transformer. Works better now. Thanks for bearing with me. Now I can move on to the cabinet.

And the answer is: I had the 1st AF miswired to the power supply, hence no B+ to that transformer. Works better now. Thanks for bearing with me. Now I can move on to the cabinet.

Is that a battery set?

Yup. I have an ARBE III and a 9-pin connector. I had the +22v volt wire connected to the C+ terminal.

Yup. I have an ARBE III and a 9-pin connector. I had the +22v volt wire connected to the C+ terminal.

I got a III or a IV don't remember....

I have 2 peerless speakers like the one in your photo. One worked, the other was super low in volume.. I opened it up and found a 1960s car radio speaker inside...

The dial may be calibrated in Meters (unit of wavelength). Wavelength is inversely related to frequency.

Tom,
I think the 0-100 dial is arbitrary. The scale on the dial is linear. If it was calibrated to either frequency or wavelength it would be nonlinear like a typical AM dial, with distance between frequencies on the dial shorter at the high end. No?

Ignore what I just said (even though it WAS brilliant). I just realized that you meant the reverse order could indicate wavelength instead of frequency. I don't think that was intended. The other one-dial sets manufactured in the same time frame--at least the ones I've seen--receive frequencies in the conventional order.

I think they used 1-100 for the sole purpose of logging stations. Probably a carryover from the three dialer. I even wonder how tight a station could stay on frequency back at that time.

On a small sample of 4 three dial units ; Freed Eismann, Grebe Syncrophase, Splitdorf and Phanstiel , the dials are all calibrated so that 100 equals 100% mesh of the tuning capacitor, hence the lowest frequency, longest wavelength. The Phanstiel has a calibration scale:
95=550 meters (approx 545 kc)*
68=450 meters (approx 670 kc)*
43=350 meters (approx 860 kc)*
17=250 meters (approx 1200kc)*

jr

*my kc calculation, NOT shown on scale.

Well, that shows that the "reverse order" on the AK Model 30 may very well have been a holdover from their 3-dial sets. I remember seeing some consumer operating instructions from 1924-1925 that explained frequencies and wavelengths. Perhaps some early commercial stations or those not on the AM band identified themselves by wavelength.

Some interesting reading here about the restructuring of the AM broadcast band and transition from wavelength designation to kc designation, beginning in 1923:
http://earlyradiohistory.us/buildbcb.htm#second
I have some radios (up to the late 40s) that indicate the meter designation, as well as kc. Old habits die hard. :)

jr

Ah, yes. I hadn't thought about this one for a while--my first radio project, a mid-1930s Stromberg-Carlson.

https://lh3.googleusercontent.com/-t6mp_xw-LL0/VOUcNVlE1bI/AAAAAAAANtY/lnOyjmTX8AI/s400/SC%2520151.jpg

Thanks for the link. It will add to my appreciation of what I've been playing with.