stern-stas: RFT 11E171; Globus-sensitivity

Hello to all forum members.
This is my first thread in this forum, and I'm looking for little help or comment.
After long period of inactivity, I'm finish restoring one German valve set -
it is "RFT Stern Radio Stassfurt super globus".
I've been seen a lot Grundigs sets with "3D klang" and good performances, but
never saw something like this RFT. It is about 40kg weight, 11 valves, and 3 valve in UKW tuner.
 Can someone give opinion what should I expect about sensitivity?
When I first saw this set, I was think when I restore them this will be one of my sets with
best sensitivity - but I'm little disappointed with performance results.
I have restored a lot of sets by now, some have sounded better then other - some catch a lot stations and has only 4 valve fitted.
I was expect that this 11 valve set will be much better performer then any of my sets.
I'm change all capacitors, some valves and few open circuit resistors, and set spring to life,
but catch only 4-5 stronger stations on UKW.
Is it normal for these early FM radios, or I have alignment trouble?
Thanks
Bero

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Dear Berislav,

I have no special Experience with " East German Stuff", but they normally schould be near or the same of the Standard at that Time.But i found one hint in the Diagram.

The Set is equipped with a Switch local - long Distance. This is the Button U-F located between
U ( UKW ) and K ( KW or SW ).

It looks like it needs to be pressed together with "U" to have full Sensitivity. If not pressed, the Sensitivity is reduced.

Maybe this helps,

Best Regards from Berlin,

Henning

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Thanks for reply Henning
Yes, it is one more button there - "UKW FERN".
This button starts to drive 3-th valve in UKW tuner.
But even with this button pressed, there is not any betterment on empty
space between stations - only loudness  hum.

Here is magic eye response on local station (attachment 18jpg)

But all adder stations have tight magic eye response,
and it's same on MW and KW (attachment 17jpg)

I am not old enough to know the sound and response of a good valve radio so its
difficult to me to judge if a radio is faulty or it's just a poor performer.
But I think that magic eye must response lively on each range and part of scale,
and not only on strongest stations.
Regards
Bero

Attachments:

• P1010018 (65 KB)
• P1010017 (73 KB)

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Dear Berislav,

the Pictures of the Magic Eye look good for me.
About the Question what to expect in Sensitivity: We do not have the Specification for this Set, but many other Companies in West Germany used the same UKW Tuner in different Sets, and the Difference between the Sets are more on the AF Part, just like You see here. ( 2  EL 84, 5 Pushbuttons for Sound Variations.)

Just the Number of tubes does not say much. ( use ECC85 instead of 2 EC92 saves one, use one ECL 82 instead 2 EL 84 and the Driver Tube saves 2, and use Selenium Rectifier saves one. )
that means, basically it is the same as a 7 tubes Set.

The only Difference is then a second IF Amplifier ( EF89 ).

I think it is a good Idea to check this Set again a Standard Set from that time ( if You have ), with the same Antenna. If this Set is worse than the Other, You schould think about, what Parts have been replaced. Replacing Tubes in IF Amplifier can make it nessesary to realign the IF Stage. But we do not have the Alignment Procedure, and i don't know, if You have the Equipment and the Experience with Alignment.

You also schould check all relevant Voltages, to see, if any further Defects are there.

Hope this helps

Best Regards,

Henning

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 I have two-page alignment plan for this set, but I think that some pages missing.
(look at attachment)
There is "Instrument I" and "Instrument II" mentioned,
and in text write "siehe Skizze". I don't have these "skizze"
and I suppose this is a data sheet where is ratio-detector described.
I understand almost everything in text except :
"Die Schwingspannung soll uber den Bereich 2-3 V betragen"

What is meaning "Die Schwingspannung" and where to put probes to measure them?

Regards

Attachments:

• 11 E 171 Abgleich 1 (67 KB)
• 11 E 171 Abgleich 2 (47 KB)

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Dear Berislav,

to have the Alignment Instruction is a very good point to start.
Please upload these Information to the Model if You can, or i can do that for You. In that case can You please make good scans and mail them to me.

"Schwingspannung" is Oscillation Voltage, but i am not shure, how to measure and at what Point.

About Instrument I and II i found something similar. Please look at Radio Model "Imperator W955" from "NORA". Find the Circuit Diagram, in the upper right Corner You see 2 Meters, one is for Ratio Detector Balance, the other one for Ratio Voltage. ( across Ratio Capacitor ).
Maybe this helps.

Before making any Alignment please replace the Ratio Capacitor with a new one.

Please note that the IF Frequency is 6.7 Mhz, while most Sets have 10,7 Mhz.

If You need a Translation of the Alignment Instruction, i can do that for You. Just let me know.

Best Regards,

Henning

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Many thanks Henning.
Yes, probably is something like that on this 3-th missing data sheet.
I will try to realign the set, but still didn't 100% sure where connect
this ratio detector instrument in my case.
I will upload these alignment instructions on RMorg.
About translation of alignment instructions it won't be necessary - I can
understand almost whole text, only couldn't find in dictionary "Schwingspannung".
About results you will be informed.
Thanks
Bero

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Dear Berislav,

today i posted a new Thread in Radiomuseum.org, in German Language, to
- ask for complete Alignment Instructions.
- ask for Specification Sheet or similar to find out, what UKW Sensitivity to expect.

Maybe we need to wait some time, and see what the Results are.

Best Regards,

Henning

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I knew it's something wrong.
There is a basic circuit schematics in RMorg wrong (look model schematics nr. 1)
There is ratio elko (5uF) turn in reverse position with + pole to anode plate.
On 3-th sheet (which upload mr.Wolfgang Eckardt in meantime) is good visible like it should be correct way with +pole to the chassis (abgleich 3).

Thanks to mr.Wolfgang Eckardt for data sheets,
and special thanks to Henning for help.

Best regards,
Bero

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