erla and what is it?

[Buzzsaaw]

Question for you that might have seen this model.

I've been getting back with all my "started" radios for restoration. This ERLA upright is on the bench. As I was removing the chassis I noticed.. hay.. no Antenna!.. There's two leads coming out the back of the chassis and hanging down below the board that the Chassis was mounted to. Grabbing the flashlight, I could see were there's a mark on the underside of this board where possibly the Antenna could have lived. Here's a pic looking up at the bottom of the Chassis mounting board.:



You can see the 3 holes for the chassis mounting screws and over to the right what looks like a large slot I presume is for the speaker wires (5) and the power cord. You can see the "band" from left to right where the antenna could have been.
I thought of buying a wave magnet or some such antenna but finding out just what was there would be interesting. I could also build one using a board form of the appropriate dimension and winding a coil on.

But I'd like to find out what is "original stock" for this radio.

[Reece]

Looking at the schematic, this radio did not use a tuned loop antenna. The antenna coils are already in the radio, part of the circuit, under the chassis. A loop would usually substitute for an antenna coil and eliminate the chassis antenna coil. This radio would use a conventional long wire antenna and a ground. The holes in the cabinet might possibly be for some other model chassis that would use this same cabinet and could take a rotatable loop; however, loops like that weren't common until a bit later. It is possible to staple a wire just inside the perimeter of the rear of the cabinet, and connect one end to the antenna lead, but it's not really a loop. It would probably work OK but not as well as 10 or 15 feet of wire inside the house or a real outdoor long wire antenna.

[tube mania]

Thats one very fine radio...a real keeper and I notice that little Denmark made its 'fingerprints' on the America radio-industry in these early radio-dayes...

Peter L. Jensen dedicated his life to innovation and today’s Jensen® musical instrument speakers continue the essence of that innovation. Peter L. Jensen was born in 1886 in Denmark and came to America in 1909. He was instrumental in the development of the "Magnavox", the first loudspeaker. Magnavox speakers were predominantly used for public address systems and were first used in 1919 to amplify President Woodrow Wilson's speech in San Diego. Peter Jensen later founded Jensen® Radio Manufacturing Company and produced speakers for both military use and radios.

In the mid-1940’s Leo Fender developed one of the first guitar amplifiers and chose Jensen® speakers for their excellent tone. Throughout the 1940’s, 1950’s and most of the 1960’s, Fender®, Ampeg®, Gibson® and all the other major amplifier companies used Jensen® musical instrument speakers until Jensen® stopped making them in the late 1960’s.

In the late 1990’s, under a licensing agreement, SICA Altoparlanti, an Italian speaker manufacturer, commenced production of the legendary Jensen® speakers. These Jensen® reissues are made to the same specifications as the original Jensen® speakers used by Leo Fender and others.

The Jensen® name is synonymous with classic vintage tone, and is the pioneer in modern state-of-the-art speakers today.

[Buzzsaaw]

Thanks,

Looking at the inside of the Chassis I don't see any loop antennas. The antenna switch (see the schematic listed in one of the above posts) has one of these wires that stick out the back of the chassis going to it.. It switches to one of the 4 bands tank circuit. :





The lower photo shows the two leads coming out. They were hanging down in close proximity to the "band" that can be seen under the support board for the chassis. So, I'm thinking there's must have been some kind of internal cabinet antenna Reese.

That's interesting History for that speaker, Tube mania. It sure is a nice and clean speaker. I'm going to remove it from the grill mounting for inspection. Then remove the mounting board in prep for some refinishing.

Got to buy a couple of 16mfd ecaps @ 450 or so WV too. Beats spending my money at the Bar watching football and looking at the Gals.. er.. oh.. nope.. that's wrong..

Buzz

[Reece]

There are no loop antennas in the chassis. There are antenna coils. They are some of the coils with the trimmers on them. If you look at the pages of the schematic, these antenna coils are identified on the drawing of the underside of the chassis. Before radios had loops they had antenna coils. If you think of a typical AA5 radio with a loop antenna, it doesn't have an antenna coil under the chassis but does have an oscillator coil under there. The loop antenna takes the place of an antenna coil.

[Buzzsaaw]

Thanks Folks,

Reese posted the link to the schematic for this radio in one of his posting (above) and it's real accurate!

After I got some of the Dust balls out I noticed a little funny looking round deal-e-O!.. It's a durn battery!.. Use for biasing the First Audio/Detector Tube (75).. and hooked to the variable arm of the Volume control pot... That's neat!

What should I use to replace this little single cell battery with? It's 1.5 volts and has a part number of 1928..?.. No, I didn't measure this one yet.. I bet it's dead as a door Nail! Nice little holder too.

It's a little hard to see in my picture. It's just South of the Diagonally mounted Blue Ecap and it's on the terminal strip. The holding clip is to the left of the actual round battery.

Buzz

[Electronic M]

Watch batteries work well I hear. I have a Grunow tele-dial table set awaiting my attention that has one of those dias cells as well.

There was a good article in ARC (antique radio clasified) a while back on those bias cells that you may want to read.

[Reece]

You'll find a lot of ideas about how to work around these bias cells. They were used in some radios from around 1936 to just before the war, and then pretty much disappeared. They were a good idea for providing a steady negative grid bias, but they can eventually wear out. Some try to rejuvinate them by injecting water, others use a watch cell as Tom C. noted: you'd dig the guts out of the old cell and modify it so that the watch cell could be used in the old holder, with the negative terminal towards the 75 tube grid. Yet another way that's easier and will probably work fine for you is to just replace the 1 meg resistor in that line to the grid with a 10 meg from grid to ground and leave the old cell in there for looks but disconnected.

A grid will collect electrons and bias itself negative but unless there's a way to bleed some of them off it will become too negative and tend to cut off the tube or cause erratic action. The high value resistor will bleed off the excess. This is not the most sophisticated way to get grid bias but it should get the job done.