saba: 455WK; Schematic and apparent circuit changes

Greetings Collectors and Restorers

During recent posts to forum thread Meine Kartei (id=36275), by Herr Denoth and Herr Boeder, and an item that I had also added, it was suggested that I post this request to determine if any member may have experienced similar events while attempting to repair and restore a Saba model S 455WK that is in excellent overall condition.

Herr Denoth and Herr Boeder (and Mr Ernest Erb) discussed several items - one of which listed the merits of having an individual member's collection of models made available for on-line search by other members for various reasons. Very good supporting points were made to allow for this procedure. In this specific instance, I have begun a very slow search by reviewing the collections that are available to see if I am able to more easily determine who may have a "functional" model Saba S 455 WK radio to contact directly for repair assistance or for other specific data??

Would the existing software programs allow an individual member to make his collection data available to the entire membership (at his option), and with some specific items restricted - if he desires? At this time, I must review each/every member's collection data to see if he has the specific model that I am interested in.

Presently, I have detected several items that do not agree between the schematic and the actual radio. Additionally, many of the capacitors have no rating data on them . . .only what appears to be model number/item number stamped on them.

I have seen very little technical information on the forums that relate to the early receivers with the variable bandwidth circuitry.

Mit freundlichen Grüßen,
Respectfully,
Robert

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Good morning Robert,

I own an electrically good set, but it's definitly dead, because the capacitors in the IF-filters are the reason for the problems. These capacitors looks like ceramic disks but it's a silver-mica compound. It's very difficult to reach this pieces in the filter cans. The complete chassis must dismantle before - too much work for my low spare time yet. So im very sorry :-(

Greetings

Eilert

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Good Morning Eilert,
I agree that it does take some time to get the chassis out of the radio - however, once out, the "cylinder covers" remove easily enough. It appears as though MANY years ago someone (added. . .may have. . . .) intentionally adjusted "full out" some of the trimmer caps. I have read years ago that there were "programs" instituted by both War Ministries -mine and yours- to . . . ."seriously disable" any broadcast receivers that had LW or KW capabilities which could adversely impact War efforts.

Eilert, Is it possible this receiver may have been "disabled" some time nearly 60 years ago and was never "restored" for whatever reason??

I do know that the capacitors appear to be the original, and the tolerances are incredible for the year 1938. . .187 pF,220 pF, and 440pF all have +/- 2.5%

The variable bandwidth feature, and tone control seem to function normally.

Mit Freundlichen Grüßen,
Robert

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Hello Robert,

that's an interesting question, but for the answer you must know the complete history of your set. In the from the german forces occupied countries at WW II the radio repair shops became the order to a "discrete" disable of the shortwave bands in the radio's they should to repair. For Chechoslovakia this is confirmed in a german collector book (G.F. Abele, vol. 4, p. 223).

At the other hand, during the war time it was for a german listener not allowed to listen to the transmissions from the enemy (eg. BBC London). This was a punishable behavior! Further details you can see here (in the german forum):

http://www.radiomuseum.org/dsp_forum_post.cfm?thread_id=5212

I'm sorry, but I am unable to check out the problems of your set 5000 miles away. For serious diagnostic it should be better the radio are here on the table and I take a look into them ;-)

I hope, we will find here another members with experience to solve the problem.

Have a nice evening

Eilert

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Good Morning Eilert,
Thank you so much for the amplifying data. I believe that if any repair attempts would have been made, the technician would have most assuredly have removed one of the 2-section repair cards stapled inside the radio. Since they are still mounted on the rear face of the front panel, it is most likely that an inexperienced individual (or repair technician) would simply disregard removing one of the cards to send it to any Saba office.

I apologize for being too hasty in my request for assistance, since I am awaiting some silver-mica caps which are as closely rated to the originals as possible. If there any members who have replaced them, it would be helpful to know how critical the values should be to maintain the 487kHz for the ZF.

I hope to report success soon, and stand ready to assist any other member who may be interested in my experiences (with many detailed photos of components).


Respectfully,
Robert

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hello Robert,


additional you can find, two origin. Saba Prints. First the Diagramm wihout Dimensions. Second, the Partlist with Postition Numbers and Dimensions.

I dont now, if the Numbers the same as i the Set on the Parts.

Maybe it is helpfull for you.


What is your Problem abaud the IF frequency?
Recommendet is 487 Kc ,  plus minus 2 Kc.(recom. knoll)

But all Circuits must be on the same frequency.

a question to the position off the Trimmer Caps.´s
Was the Set betwen 1939 and maybe 1955 locatet in W-germany?

Greadings from Franconia

Hans M. Knoll

Attachments:

• SABA 455W Circuit (265 KB)
• SABA 455W Partlist (302 KB)

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Hello Hans,
Thank so much for the Circuit data and the parts list. Also , please accept my apology for not posting within the last few days I received from Herr Werner Hauf - one of our members - also a parts list, schematic and other pages from original SABA technical data. I am still reviewing the pages.

When I began to replace capacitors, all Saba caps have only part numbers on them; nearly every capacitor under the chassis appeared "undisturbed" from original; the few Frako electrolytics have printed ratings. The 2 power supply caps were original Saba 580/81-14A, and the block condenser was NSF (maker) with PN 580/82 2x0.85uF

Reference the IF: On cylinder 2 (Mixer stage), both trimmer capacitor adjustment screws were adjusted very far "out". I suspected the IF to have a critical tolerance - considering the +/- 2.5% tolerance on the edge of the silver-mica caps.

I am still investigating ownership and location of the receiver in its earliest years - I have been told the original owner was a gentleman who was about 80 to 82 years old. . .name was Robert Rammings - a civil engineer for the city of Lockport, New York

One last item, all 5 of the tubes were the original Telefunken with date codes of ul/9-38, ul/9-38, hg/10-38, hg/10-38, and EL11 output coded 141 (12-39)??

The large circular silver-mica caps (187pF and 440pF) at the bottom of cylinder 3 (oscillator), appear to have cracks in the sealant. Awaiting replacement.

Mfg,
Robert
Also thank you so much for the Perlonseil threads for my 5040W/3D that Herr Michael John forwarded with the dial glass and other parts.

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Hello Robert,

thanks for your answer. The reason for my quenstion, abaud the history of the set is:

Original was the Set designed (1938) to receive on Mediumwave Frequencys between 510 to 1500 Kc.
In 1950 the Medium  Range was exdendet  to 510 to 1602 Kc. 
See here my words  in german:
Der Wellenplan von Kopenhagen.(1)
Im Nachgang zur Welt-Funkkonferenz von Atlantic City / USA im Jahr 1947, wurde in der Zeit vom 15.Juni bis 15.Sept. 1948, in Kopenhagen ein neuer Wellenplan für Europa erarbeitet. Benannt nach der Stadt Kopenhagen, trat er am 15. März 1950 in Kraft. Er löste den im Jahr 1933 in Luzern beschlossenen Vertrag ab.

Many Stations in W- Germany  was moved above 1500Kc.
For example:
nach Plan:
NWDR ( nordwestdeutscher rundfunk)   = 1586kHz
Nuernberg = 1602 kHz
AFN = 1554 kHz
SWF (Suedwestfunk Baden-Baden) = 1538 kHz

All the german  radios  must change from the upper end 1500 kc to 1602 Kc.
To achieve this , the "Trimmers"  must were =adjusted very far "out".
In some sets is it necessary to pull out the whole capacitors and Trimmers  on the tuning condenser or reduce the winding of the coils! ( Volksempfaenger)

O.K. Robert,
 this was my Answer. I am standby for other questions.

Have a good time,  Hans

 

see also : http://www.radiomuseum.org/dsp_forum_post.cfm?thread_id=36986

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