MW.E.c. and E.U. a2 for operation

[Quatsch]

Is this the component that was removed? Three of them are listed in the manual, Item Nos. (155, 167, 176) One is 353 kHz and two are 352 kHz.

If that is correct it is a blessing as these seem to be hard components to find.

I believe so, the image matches those of German made xtals of the era that I have seen. The glare on the printing makes it hard to read the marking other than the telefunken symbol.

[17thairborne]

Good news then. Fewer parts to source if they are bad

[Funksammler]

I don't think the X-tals were removed in the yellow stripe version, they just changed to vacuum type X-tals. The main change was in the design of the HF filter. In the original design, they were worried that strong short wave broadcast transmitters operating on the mirror frequency (between 1.5 and 3.7 Mhz) would get through so they filtered these frequencies out. In practice these broadcast transmitters were not an issue, so the extra filtering was dropped.

Generally X-tals are not components that you have to worry about, they are pretty robust mechanically and electrically.

regards,

Funksammler

[17thairborne]

Funksammler,
Thanks very much for clarifying. My MW.E.c is in customs since 10 March and should be on its way any day now. We followed the advice given regarding packing and customs labels. For antique radios, the customs is minimal (I hope).

Released from customs this morning.

[Funksammler]

When shipping to the US, always list it as: "Old collector's piece (<description>) of historical interest, as of 9705.00.0070. Non-functional, for display purposed only. Over 70 years old"

I think you do not have to pay any import duties using this customs code.

regards,

Funksammler

[17thairborne]

I think that is what Willem did. It is now on its way to my home. Hopefully it will arrive in 3 days. Then I can begin with careful inspection according to the recommendations posted by Yuri in the Communications Equipment section, copied here for continuity:

1. Do NOT turn it on to see if it works.

2. Take all the tubes out.

3. Clean contacts with a good contact cleaning solution and a lint-free cloth.

4. Slowly increase filament voltage and measure on the filament termini.

5. Slowly increase anode voltage and measure on the anode terminus and ground.

6. Test the tubes on an RPG 4/3 (they are not very expensive these days and are usually available on Ebay)

7. Put the tubes back in, then slowly turn up the filament to CORRECT voltage. Filament being too low or too high is not good. Make sure the filament voltage is correct on the termini.

8. Turn up the anode voltage

[17thairborne]

Since I also have an Umformer E.U. a2. Are there any special considerations for testing that device. Here is what Funksammler posted on the WAF:

Cleaning the bearings can't do much harm, although if they are not noisy they are not a real problem. you can easily lift out the motor-generator out and gain access from the sides. First however I would clean the commutator and check that it not too rutted. A bit of emerald paper and some contact spray should do the trick. The irregular running is probably due to a dirty commutator. If you look closely, you will probably see some sparking in time with the variations in running. Also check the caps on the motor generator, but usually these are OK. After cleaning, let the umformer run for an hour or so to give it a chance to build a nice patina. The more it runs, the better it gets!

Are their any other considerations when testing the output voltages when not connected to the radio? Safety always!

[Quatsch]

I don't think the X-tals were removed in the yellow stripe version, they just changed to vacuum type X-tals. The main change was in the design of the HF filter. In the original design, they were worried that strong short wave broadcast transmitters operating on the mirror frequency (between 1.5 and 3.7 Mhz) would get through so they filtered these frequencies out. In practice these broadcast transmitters were not an issue, so the extra filtering was dropped.

Generally X-tals are not components that you have to worry about, they are pretty robust mechanically and electrically.

regards,

Funksammler

Oh yeah, now I get it. The Germans enclosed the xtals in glass tubes just like other vacuum tubes, not just in metal/phenolic cases. In the allies case, most xtals were contained in a gasketed phenolic box contraption that does not incline to reliability 70 years on.

[Quatsch]

Since I also have an Umformer E.U. a2. Are there any special considerations for testing that device. Here is what Funksammler posted on the WAF:

Cleaning the bearings can't do much harm, although if they are not noisy they are not a real problem. you can easily lift out the motor-generator out and gain access from the sides. First however I would clean the commutator and check that it not too rutted. A bit of emerald paper and some contact spray should do the trick. The irregular running is probably due to a dirty commutator. If you look closely, you will probably see some sparking in time with the variations in running. Also check the caps on the motor generator, but usually these are OK. After cleaning, let the umformer run for an hour or so to give it a chance to build a nice patina. The more it runs, the better it gets!

Are their any other considerations when testing the output voltages when not connected to the radio? Safety always!

I am inclined to use synthetic lubricants where applicable, they are simply superior.

[17thairborne]

Thank you!

[17thairborne]

Continued

Demodulator and LF Amplification Stage

Through unique use of the electrodes of tube (20), the following tasks are accomplished. The retarding grid plug cathode is used as a diode to acquire the LF alternating current in the operating mode "Tn" and in the 900Hz alternating current in the "Tg" and "Tg with audio filter" mode. The resulting audible oscillations are then enhanced in the triode system's grid-steering grid cathode. Finally the diode distance-retarding grid anode is used to achieve AGC voltage.

The modulated IF oscillations in the "Tn" and respectfully the IF oscillations with the support oscillations of the 2nd heterodyne stage (with "Tg" and "Tg with audio filter" mode) are carried over the IF transformer (184/184 a) to the diode distance-retarding grid cathode of tube (20). The LF oscillations emerge at resister (82) that is bridged by the IF oscillations of capacitor (83). These are directed to the grid of tube (20) across capacitor 112 to the volume control potentiometer (11) and later to the grid of tube (20). The potentiometer can only function in the "Tn" mode, in the other two modes it is adjusted always to maximum through the selector (39c). The necessary grid-cathode bias voltage are taken from resistors (85, 86), The capacitors (84, 87) supply bypass for the LF oscillations. The retarding grid-anode, which acts as a diode, supplies the AGC voltage which is taken from load resistors (96, 97) and is subsequently multiplexed into stand alone amplification control by the grid bias voltage of tubes (14,18,19).

[17thairborne]

The radio and umformer arrived today. Here is the umformer

[17thairborne]

Interior

[17thairborne]

The pin configuration on the male portion of the cable is 180 degrees out from the umformer's female set up. The triangular alignment notches are out of phase. Is it as simple as moving the small set screw of the unformer from the "S" hole to the "E" hole? I am assuming that is an alignment pin with no electrical connections.

[Funksammler]

That is a E.U.a4 rather than a 2. This must have been very early in the production run of the E.U.a4 as they have removed contact number 2 from the contact strip rather than manufacture it without the contact. It looks to be in very good condition and it looks like it already has been serviced. I would be happy to try running this one without any work...

regards,

Funksammler