Model: 930A
Antique radios, Old Time Radios
930A
Country:
Netherlands
Manufacturer/Brand:
Philips; - Eindhoven; Netherlands
Year: 1931 / 1932
Type:
Broadcast receiver (Radio).
Im Gegensatz zu Radioempfängern für kommerzielle und/oder militärische Zwecke und den frühen Empfängern für Morsezwecke nennen wir hier Radio bzw. Rundfunkempfänger. Aber: Gemäss internationaler Sprachregelung führt der Radiokatalog Band 1 alle Empfänger mit aktiven Bauteilen als RADIO. Wir unterscheiden hier ebenfalls nicht, ob mit Röhren bestückt, hybrid, mit Transistoren oder/und ICs.Radio or Tuner
Mod.-ID = 7408
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Schematics etc.: 5 (for
members)
Principle
TRF (tuned radio frequency or straight receiver) with manual regenerative (feed-back) control.
Récepteur TSF à amplification directe avec réaction maneuvrable.
Geradeausempfänger mit bedienbarer Rückkopplung, die auch zum Selbstschwingen führen kann. Siehe «Radios von gestern» Seite 59.TRF with reaction (regenerative); 2 AF-stage(s)
Tuned circuits
1 AM circuit(s);
Wave bands
Broadcast- and long-waves (AM, medium- and long-waves) PO et GO (petites ondes et grandes ondes).
Langwellen- und Mittelwellen-Bereich.
Auch wenn in diesen Bereichen eine Unterteilung vorkommt - bei älteren Geräten z.B. die Antenne umgesteckt werden sollte - geht dies hier nicht daraus hervor.Broadcast (MW) and Long Wave.
Power type and voltage
AC set plus voltage range.
/ = 2 different voltages
- = voltage from-to
* = «Special»
Apparareil à courant alternatif. Tensions mentionnées.
/ = 2 Spannungswahlen
- = von-bis
* = Fabrikwahl/«Spezial»
Trafo ist nicht immer mit Primär- undSekundärwicklungen versehen. Dadurch kann das Chassis ein gefährlichesPotential führen.Alternating Current supply (AC) / 220 Volt
Loudspeaker/pwr.out
Improved magnetic speaker. (horse-shoe-type with 4 poles). Haut-parleur magnétique perfectionné (avec 4 pôle).
Vierpoliges Magnetsystem - meist hufeisenförmiger Magnet. Aus den Unterlagen geht selten eindeutig hervor, ob es das 4- oder 2pol-System oder (ab 1932) sogar ein Freischwinger ist. Zur Unterscheidung siehe «Radios von gestern» Seiten 61 und 329ff.Magnetic Loudspeaker of high quality (4 magnet poles)
from Radiomuseum.org
Model: 930A
Material
Made of different materials!
Caisse fait de differentes materiaux.
Das Gerät ist etwas ungewöhnlich (nicht nur Holz, Stahl oder Bakelit) vom Material her. Mehr war von den gehabten Unterlagen her nicht auszusagen.
Vielleicht geben Sie einen Text zu den Materialien oder dem Format (fehlen Masse?) mittels «Infos zum Modell hinzufügen» ein?Various materials
Shape
Tablemodel, high profile (upright - NOT Cathedral nor Tombstone).
Dimensions (WHD)
410 x 470 x 170 mm / 16.1 x 18.5 x 6.7 inch
Valves / Tubes
4:
E438
(more
for members)
Notes
The Philips model 930A is a regenerative TRF - which is not quite clearly shown on the schematic - see here in this article about it. Philips 930A, sometimes called «Schinken» or "Jambon", has a cabinet which is made of a metal frame covered with two hardpaper panels (matère = Arbolite) with woodprint and a bakelite Philips logo covering the loudspeaker opening.
930A Rueckwand.jpg
930A Innenansicht.jpg
More pictures
More information on
930A (Philips; - Eindhoven; Netherlands)
This Philips 930A set has one of the most beautiful cases ever made, so I decided to take a closer look at the schematic.
The schematic is one of the simplest around with an input grid-leak detector, an audio preamp triode, and an output pentode. But the inductor load at the grid leak detector made me think that some regeneration (Rückkopplung) was designed in, simply by the presence of an inductive Plate load.
This use of regeneration would fall under the category of "trade secret", so there is no need to change the classification of this radio from "TRF without reaction" to "TRF with reaction". Philips probably wanted it that way.
According to F. E. Terman's 1955 Electronic and Radio Engineering 4th edition page 427, when an inductive plate load is presented to a triode, the input conductance at the grid becomes negative below the frequency of resonance at the plate. Below resonance the impedance of the tank circuit is inductive.
This resonant frequency may be very high because the only capacitance at the plate is the self-capacitance of the load inductor and the Miller-multiplied grid-to-plate capacitance. In total, this should be under 30pF, if the inductor is not simply a high inductance choke (>1mH).
The photos that were posted under this radio did not clarify for me the value and the location of this inductor.
I wonder if an owner of this radio could tell the Forum what is the approximate value of the inductance, and what is it's position relative to the other inductances. If you own an inductance meter such as the Rhode&Schwarz BN6100, it would be great to know the the self-resonant frequency of this inductor too.
Another simple test could also show the effect of the inductor on gain: Shorting out the inductor with a short wire should lower the output volume. If using a foot-long aligator jumper, you should twist the wire tightly to avoid making a loop that might couple to the input coils.
Regards,
-Joe
More...
I have in my collection two different versions of this radio that puzzels me a bit. The normal case seem to be that this radio has a Bakelite/Philite-base mounted at it´s bottom. Now I have found out that one of the radios has a base entirely made of black painted wood instead.
A fellow collector in Sweden claims that this is sometimes the case and that it is original and factory made. There is of course still the possibility that this base does not belong to the radio from the beginning but has been used to repair it when the original base was damaged, however it looks like it should be there and that no fiddling has been done.
Assuming that this base would be factoryassembled original gives room for at least three different explanations:
1: Either of the two bases was used in early series production, but later abandoned due to costs or other practical reasons.
2: The normal production of Bakelite/Philite bases was for some reason interrupted - be it a shortage of material, a strike among workers or whatever - forcing ahead an alternative solution for the base manufacturing, so that they still could produce the radiomodel.
3. The different bases were used in two or more different production facilities in different countries but radios from both factories may have been sold in any country.
There must be many Philips 930 A among the members in RMorg so now to my questions:
Is there anyone else who own a model 930 A (or 930 C, for that matter) with wooden base?
Does anybody know in which countries the Philips 930 A (also 930 C) was produced? When searching for the model several countries appear in the list, but not exactly same for 930 A respectively 930 C, and this puzzles me a bit.
I try to attach pictures with the two different bases below:
More...
