Hi. I have recently gotten my hands on what I think is a very old radio:

I am interested in how this device works. Inside the case is, among other things, a black cylinder containing some circuitry and on its side is a schematic:


I have tried making a hand drawn copy:

I am having a hard time trying to find out what some of these schematic symbols represent and was wondering if anyone in here had knowledge in that area. I am guessing the following is some sort of vacuum tube (a triode?):

I have no idea what the following are:


And finally I am a bit confused about this set of capacitors that are connected by an arrow as if it is some kind of twin variable capacitor:

Sorry if some of the images are a bit unclear.

 

I suspect the first is a triode (Wikipedia):

 

hi Andreas,
I clear photo of the front panel of the radio box, so that we can see any symbols, would be helpful.

E

 

hi Andreas,
I clear photo of the front panel of the radio box, so that we can see any symbols, would be helpful.

E

Of course . I have also taken some more photos of the inside in case that can be helpful. The connector holes on the front must be (at least some of them) for the very fashionable headphones that came with the radio. I am thinking the dials on the front must be for the variable capacitors in the curcuit.

 

hi,
I would try here.
https://www.vintage-radio.net/forum/showthread.php?t=39439

E

 

That is an old Valve based Tuned Radio Filter radio receiver. Those sockets use Plug-in Coils for different frequencies. Only AM, may be CW with addition of a Hetrodyne oscillator.
Please check your extract of the schematic. There could be mistakes.

 

?BBELTSPOL?
What is the total word here?
Is there a manufacturer named on this part?

 

This is a TRF receiver (Tuned Radio Frequency) with regeneration.
The circles in the schematic marked A, I and U are the tuning coils. They are tuned with the big dual variable capacitor in the middle of the receiver. The triode on the left is an RF amplifier with a tuned circuit on both the grid and the anode. The next triode is the detector, There is no negative grid bias so it only amplifies the positive half cycles of the rf carrier. The capacitor C2 from it's anode to the the previous triode is adjustable regenerative positive rf feedback. It increases the sensitivity and selectivity of the received signal. There is an choke (inductor) on the anode of the second triode to block rf and then the primary of an audio matching transformer. The other end of the primary would connect to the 45V battery +. The secondary of that transformer is connected to the grid of the output triode. The other end of the secondary goes to a connector. This would have been plugged into a negative tap on a grid bias battery. The positive of the battery would have been plugged into the connector above it in the diagram. The headphones would connect between the anode of the output triode and the 45V battery +. I don't know what the circle marked 7 is. It could be a small light bulb to limit the current through the phones.
The big, round battery is for the triode filaments and would have been connected between the second and third connectors from the bottom right on the schematic.
Note: The 45 volt battery is either connected the wrong way round or the plugs on the wires have been switched for some reason.
A grid bias battery is six A cells connected in series with connector sockets at each junction.
Regards,
Keith

 

What ever you do, that is a collector's item that deserves to be preserved in a museum.
Every component has historic value, the two batteries, two pair of high impedance headphones.
Interesting that the batteries were given names such as "CONRAD".

Here are some links and places that could help.

Ottawa Vintage Radio Club - some schematics here that will help you understand how vintage tube radios work.

http://www.aef.se

https://www.aef.se/Amatortidningar/Popular-Radio/Year_1940-1949/Popular_Radio_1942_nr_10.pdf

https://data.collectienederland.nl/search/?page=82&qf[]=nave_material:metaal&q=Leeuw,+van+der

 

That used to be a first real radio project when I grew up, before Super-Hetrodyne!
It was a progression from the galena 'Cats Whisker' first.
Max.

 

I am impressed. At first look, I thought it was a reproduction radio due to the very good condition of the outside case. Absolutely astounded that it is the real deal and for it's age it is in incredible condition even down to the paper coverings on the battery. Truly amazing condition.

 

In the upper left, what are the 2 components with the screw terminals on the ends? 4-pin UX-base 80 rectifiers have 2 "thick" and 2 "thin" pins but it doesn't look like this base has that. The alignment of pin sockets does not look square either. The circuit diagram on the large -BBELTSPOLE- can is decorative and not indicative of this particular radio. The back of the "can" only has 3 terminals. Is this another capacitor? or a potentiometer?

 

That is an old Valve based Tuned Radio Filter radio receiver. Those sockets use Plug-in Coils for different frequencies. Only AM, may be CW with addition of a Hetrodyne oscillator.
Please check your extract of the schematic. There could be mistakes.

Interesting. Nice to know exactly what this thing is. There might very well be some mistakes in my schematic extract even though I cannot find any at the moment. Some of the writing is pretty hard to distinguish and there are some symbols I have not included in the drawing because they just look like splodges of ink. However, I have just noticed that the two schematics (which I previosly assumed were probably the same) are actually a bit different. The knob to the left is probably a switch for choosing between the two. Here is this other one:

 

Hello,

Could it be the full name is DOBBELTSPOLE ?
That could mean double coil.

Bertus

 

?BBELTSPOL?
What is the total word here?
Is there a manufacturer named on this part?

I can't really tell what the entire word is. The side of the cylinder is not easily accessible and I am not really keen to take it apart since I have only borrowed the radio. However, I can at least see that it says "?BBELTSPOLE". "SPOLE" means "coil" in Danish and "?BBELT" might be "DOBBELT", meaning "DOUBLE", but I don't know what a DOUBLE COIL might be...

I can't really find the manufacturer's name anywhere on the radio itself either, but I can see that the manufacturer of the 1,5 V battery that is inside the case (along with a 45 V one) is Hellesens. Doing some googleing I found out that this company, apart from batteries, have also manufactured battery driven radios, so I am thinking this one might well be one such.

 

The 2 schematic diagrams on the BBELTSPOLE device have nothing to do with this radio. Dobbetspole makes sense, 2 variable air caps and a tapped or dual inductors for tuning. Is the can a switch and not a free turning shaft as on a potentiometer? How many switch positions?

 

This is a TRF receiver (Tuned Radio Frequency) with regeneration.
The circles in the schematic marked A, I and U are the tuning coils. They are tuned with the big dual variable capacitor in the middle of the receiver. The triode on the left is an RF amplifier with a tuned circuit on both the grid and the anode. The next triode is the detector, There is no negative grid bias so it only amplifies the positive half cycles of the rf carrier. The capacitor C2 from it's anode to the the previous triode is adjustable regenerative positive rf feedback. It increases the sensitivity and selectivity of the received signal. There is an choke (inductor) on the anode of the second triode to block rf and then the primary of an audio matching transformer. The other end of the primary would connect to the 45V battery +. The secondary of that transformer is connected to the grid of the output triode. The other end of the secondary goes to a connector. This would have been plugged into a negative tap on a grid bias battery. The positive of the battery would have been plugged into the connector above it in the diagram. The headphones would connect between the anode of the output triode and the 45V battery +. I don't know what the circle marked 7 is. It could be a small light bulb to limit the current through the phones.
The big, round battery is for the triode filaments and would have been connected between the second and third connectors from the bottom right on the schematic.
Note: The 45 volt battery is either connected the wrong way round or the plugs on the wires have been switched for some reason.
A grid bias battery is six A cells connected in series with connector sockets at each junction.
View attachment 216483Regards,
Keith

Thanks a lot for the in-depth answer. There were a lot of things I didn't know.

 

What ever you do, that is a collector's item that deserves to be preserved in a museum.
Every component has historic value, the two batteries, two pair of high impedance headphones.
Interesting that the batteries were given names such as "CONRAD".

Here are some links and places that could help.

Ottawa Vintage Radio Club - some schematics here that will help you understand how vintage tube radios work.

http://www.aef.se

https://www.aef.se/Amatortidningar/Popular-Radio/Year_1940-1949/Popular_Radio_1942_nr_10.pdf

https://data.collectienederland.nl/search/?page=82&qf[]=nave_material:metaal&q=Leeuw,+van+der

View attachment 216484

Thanks a lot for the links. My grandparents borrowed me this radio they had found hoping I could find some information about it and rest assured that it will then be given to someone who appreciates it .

 

In the upper left, what are the 2 components with the screw terminals on the ends? 4-pin UX-base 80 rectifiers have 2 "thick" and 2 "thin" pins but it doesn't look like this base has that. The alignment of pin sockets does not look square either. The circuit diagram on the large -BBELTSPOLE- can is decorative and not indicative of this particular radio. The back of the "can" only has 3 terminals. Is this another capacitor? or a potentiometer?
View attachment 216488

The text on the uppermost of the two components is MIKAFARAD. As far as I can tell from a quick google it is some kind of capacitor of german manufacture. The text on the other one reads "KONSTANT" ("constant") on one side, but I can't read what it says on the other side.

I don't know what the thing at the bottom right of the image is, but I have taken a better picture of it. It has some letters around the edge (G, F, A and F as far as I can tell):

I don't know what the "can" is, but as "SPOLE" means "coil" in Danish (the radio and I are from Denmark) I am guessing it might be some sort of coil. As bertus has also mentioned, the full word might be "DOBBELTSPOLE", meaning "DOUBLE COIL", though I don't know what that is.

 

I

The text on the uppermost of the two components is MIKAFARAD.

I went to school with a Mike Farad, he had quite the capacity to absorb knowledge.
Max.