The radio is housed in a wooden case with glass dial, plastic trim, and beige grille cloth. The appearance is typical of German sets of this vintage. It is larger and heavy than average.
It receives AM broadcast, long wave, shortwave, and FM broadcast bands. The FM is monophonic. Stereo was not introduced until the 1959 model. The AM bands use a 460 KHz IF frequency and FM uses 10.7 MHz.
It has an EM35 "magic eye" tube to assist in tuning in stations, a common feature on higher-end German radios.
There are two bandwidth settings, selected by pushing or pulling the volume knob.
There are five speakers -- one large one with good bass response on the front left, an electrostastic tweeter on the front right, and two midrange speakers on each side of the cabinet.
The "direction finder" is an unusual feature. When the Direction Finding button is depressed, it switches to an internal antenna which is rotatable over a range of 360 degrees via the Direction Finding knob. An azimuth type indicator shows the orientation of the antenna. Via the tuning eye you can determine the direction of maximum signal strength.
As received the radio was electrically complete except for a line cord (a cheater plug type). The cabinet was in good shape although the top has some crazing of the varnish and wear in spots. It was quite dusty inside with no signs of any previous restoration or repairs.
Nordmende (short for Norddeutsche Mende-Rundfunk GmbH) is the manufacturer. It is one of the most respected and collectible Germany radio manufacturers, alongside Grundig and Telefunken. The company was formed by Martin Mende in 1947 and manufactured radios, televisions, and test equipment. It was a family business run by the founder and later his sons. Facing increasing competition from larger rivals it was sold to the French company Thomson Brandt in 1977.
The model name, Tannhäuser, comes from the opera by Richard Wagner. Several Nordmende radios of that era had operatic names such as Carmen, Caruso, and Rigoletto.
The original German retail price for the radio in 1957 was 478 DM. At that time this was approximately US$114 and with inflation equivalent to about US$768 today.
This is the US model. As compared to the European model, I think the only visual difference is that the front and rear controls and connectors are labelled in English and the line cord is a North American type. The input line voltage is switch selectable for several voltages so it could be used anywhere in the word. I've read that the German model had a limited FM band that only covered 87-100MHz rather than the full 88-108 MHz used in North America. This web page has a design for an FM band extension circuit.
I did some resistance checks of the AC input and found that the fuse was blown. Not a good sign but it doesn't mean a lot. With the power switch on the resistance looks okay so it should be safe to power it up.
I powered it up slowly with a variac and current meter in 10 volt steps recording and watching the current. This is in case a part such as an electrolytic capacitor should fail by shorting and cause other damage such as destroying the expensive power transformer. Slow power-up can also re-form old electrolytic capacitors that have not been used for a long time.
At around 50 volts input I could see a pilot light glowing and some tubes starting to light. At 70 volts I could hear some hum from the speaker indicating the audio amplifier was working. There was some static but no stations on AM. I tried FM and I heard music! When I pressed the BC button again AM broadcast also started working -- the switch was just dirty. Overall the radio appears to be functional although I did not try all the controls. I increased the voltage slowly up to 110 volts. Current seems to be well within the 1 amp fuse rating marked on the radio.
| Voltage (volts) | Current (amps) |
|---|---|
| 10 | 0.06 |
| 20 | 0.11 |
| 30 | 0.14 |
| 40 | 0.15 |
| 50 | 0.18 |
| 60 | 0.21 |
| 70 | 0.28 |
| 80 | 0.37 |
| 90 | 0.44 |
| 100 | 0.52 |
| 110 | 0.61 |
Other things noted: all tubes light up, one of the two pilot lamps was not working (easy to replace). There is no noticeable hum so the power supply filter caps must be working okay. The magic eye was working but not very bright -- this is expected as these tubes do get dim after not too many hours of use. The sound quality, especially on FM, is excellent. All four speakers are working.
I decided not to press my luck and turned it off. It really needs a good cleaning of all the accumulated dust inside. All in all, good signs that this radio will not be hard to restore.
Here is a picture of a portion of the schematic I pasted together:
I scanned the schematic and did some cleanup of the images using the GIMP image editor. The don't look too bad but there are some missing pieces.
I heard back from oldradios.com. They have the schematic. From their reference number it is from Sams 638-12. I will go ahead and order it.
The radio uses European tubes which have equivalents in the North American numbering system. Here are the equivalents:
| European | American |
|---|---|
| ECC85 | 6AQ8 |
| ECH81 | 6AJ8 |
| EF89 | 6DA6 |
| EABC80 | 6AK8 |
| ECC82 | 12AU7 |
| EL84 | 6BQ5 |
| EM35 | 6CD7 |
The EM35 eye tube is one of the rare and expensive ones to replace. A new (NOS) one is about $50-$80 from on-line tube stores.
Fuse needed: 1A 250V 5mm x 20mm. I found a 2A fuse to use temporarily.
Pilot lamp is threaded base 7V 0.3A marked MF150. Looks like type 46 T-3 1/4 miniature screw base.
Did some cleaning of chassis, tubes, and front panel (what I could reach without disassembling radio).
Long wave, short wave, and other functions all appear to work okay.
Here are differences I noted between the German and US model:
You can't just pull the chassis out and work on this radio on the bench like you can with AA5 radios. However, most components can be accessed from the underside through an opening in the case after sliding out a metallized cardboard shield. I guess you have to think differently with these European radios.
It was tricky to get it apart and back together. A nut seized up and I had to take the tone switches out again, loosen the speaker board, replace the nut, and fool with them for a while until it was all back together.
The cord appears to be the standard 5/16" cheater plug. It tried one from another radio and it fit but it was quite loose. Probably best to permanently attach a new cord.
I tested the tubes and got these measurements. Some may not be accurate -- the only real test is in a radio.
| Tube | Measurement |
|---|---|
| ECC85 | 86 70 |
| ECH81 | 70 70 |
| EF98 | 110 |
| EF89 | failed short test? |
| EABC80 | 49 88 88 72 |
| ECC82 | 135 135 |
| EL84 | 85 |
| EL84 | 100 |
| EM35 | not in any of my tube charts |
I noticed while it was playing there is intermittent changes in volume. Wiggling a tube seemed to help. This will likely get fixed when radio is recapped and tube sockets cleaned.
I took a few pictures when it was on the bench.
Doing cleaning and lubricating underside of chassis.
Rectifiers are selenium in a metal can. The "experts" have conflicting opinions on whether to replace them. If they fail they should blow the fuse. If replaced with modern silicon diodes and series resistor is need to compensate for the lower voltage drop.
More pictures. These are really intended to be of use to me if I later need to check how some wiring or components were connected.
After cleaning the tube pins and sockets there are no intermittent connections there, but the BC switch still sometimes needs to be played with to get a good connection.
I see a couple of EM35 tubes on ebay, so that may be a good avenue for buying one more cheaply than the tube stores.
One wax paper cap was replaced the other day. A couple of others should be done too. Also did some cleaning of the cabinet.
Have been watching some EM35 "magic eye" tubes on ebay. They have been selling for almost the same price as from the tube stores, so I may just order one from a store since it will come from a reputable source with a warranty...
I also replaced another electrolytic cap.
Earlier today the other dial lamp started working, but later stopped again. Checking it carefully with an ohmmeter it measured as open.
I ordered some dial lamps from Antique Radio Supply.
Measured most of the resistors and did not find any that were out of spec.
I believe that wraps up the restoration of the radio. It is now ready for its new owner. Of course I will visit it occasionally.
