TeKaDe logo

The German company TeKaDe is now quite obscure. Some information can be found on the German wikipedia, but this does not mention semiconductors. The company started life in 1906 as Felten and Guilleaume but in 1912 the name was changed to TeKaDe, for Süddeutsche Telefonapparate-, Kabel- und Drahtwerke AG, which means "South German telephone equipment, cable and wire works". Somewhat counter to this name, the company specialised in wireless telephone networks. In 1981 it was taken over by Philips.

In the late 1950s and into the 1960s TeKaDe manufactured germanium transistors and diodes, some of which I show below. Information about this is scarce. Some can be found (in German) on the excellent Radiomuseum site. It states that from 1955, TeKaDe was producing high-end germanium diodes and from 1956 AF-transistors. From 1958/59 semiconductor production started at the Schwabenstrasse plant but the company ceased production in 1961/62 for economic reasons.

The company logo was usually printed on devices, but sometimes just the letters TKD were used.

I am seeking to buy or trade for germanium transistors and diodes made by TeKaDe, especially the types GST01, GST02, GFT2006, GFT20, GFT31 and GFT32. Details are given below. I also want to buy any original data books or sheets for any of their semiconductor devices.

If you know about them, or have have some devices for sale or trade, please

Ich suche die Germaniumtransistoren und Dioden die von TeKaDe hergestellt werden. Ich möchte auch ursprüngliche Leistungsblätter für sie kaufen. Wenn Sie in diesen Transistoren oder Dioden auskennen oder haben, einiges für Verkauf oder Handel zu haben, in Verbindung.


I guess that the first semiconductors that TeKaDe made were diodes, since most semiconductor manufacturers started that way. They made point-contact diodes in the GSD series: this stands for 'germanium spitzen diode'. The upper image on the right shows a GSD5/40.

However, their oldest diodes are just marked K or G plus a number, such as the G 5/61 on the lower right. I think the G stands for "glas" and the K for "keramic" or possibly "kunststoff", denoting the material of which the body is made. The qualified part number is typical of TeKaDe, except for their earliest transistors, and probably indicates a maximum voltage parameter. Many devices also have a single-letter suffix.

They made a good number of such diodes (I list with GST prefix, prefixes K and G are also possible):

  • GSD1,5/20, GSD2,5/9, GSD2,5/15
  • GSD4/10, GSD4/12
  • GSD5/2, GSD5/4, GSD5/5, GSD5/6, GSD5/40, GSD5/61, GSD5/103, GSD5/104, GSD5/105, GSD5/161
  • GSD15/4
  • GSD50/2

all of which had G and K equivalents.

I am interested in obtaining most of these diodes by TeKaDe. If you know about TeKaDe's earliest semiconductors, or have have some for sale or trade, please

TeKaDe GSD5/40 diode TeKaDe G5/61 diode

TeKaDe OA21 diode

TeKaDe also made two germanium point-contact diodes in the Philips OA series, types OA21 and OA41. My image shows OA21 which is a UHF mixer diode. OA41 was more commonly made by Telefunken.

I am interested in obtaining examples of OA41 by TKD. If you have have some for sale or trade, please


TeKaDe GST wanted

TeKaDe made two point-contact transistors, types GST01 and GST02. These used the typical cartridge case originated by Western Electric.

I am very interested in obtaining these transistors by TeKaDe. If you know about TeKaDe's earliest semiconductors, or have have some for sale or trade, please


TKD junction transistors were all in the GFT series, although some do not include this prefix on the can. GFT stands for Germanium Flächentransistor, that is "germanium junction transistor".

The GFT20 was possibly their first junction transistor. The German Radiomuseum site shows a GFT20 in a can like my GFT21 below, but their diagram shows a different 'bell' shape. They state that the device is an AF amplifier, which one would expect for a very early type. Interestingly, they list three possible qualifiers: /6, /15 and /30.

TeKaDe wanted transistor

TeKaDe GFT21 transistor

Here is a GFT21 transistor. It is painted in the characteristic red, and has the company logo and also the part number printed on it. There is no qualifier to the part number on this example.

Radiomuseum lists five possible qualifiers: /15, /15A, /15B, /30 and /30A. It also states that versions were offered for hobbyists/kits with the marking NF21, NF7 or NF8.

I am very interested in obtaining any transistors by TeKaDe in this bell-shaped package. If you know where any are for sale or trade, please


TeKaDe made an early power transistor, type GFT2006, in an idiosyncratic cylindrical package. My image shows examples with the suffix /30, there exist other suffixes, possibly including none.

I am interested in obtaining examples of this transistor with suffix other than /30. If you know where any are for sale or trade, please

TeKaDe GFT2006 transistor

I recently bought this device, marked OC15 without any manufacturer, which is clearly the same case as the GFT2006. The original OC15 was Philips/Mullard's first power transistor, from about 1954/55, in a somewhat larger cylindrical can, and is very rare. There is a Valvo equivalent type 100OC. I'm a bit sceptical that TKD were experimenting with power transistors at this early time. I'm also puzzled by the code 0948, which cannot be a date of 1948!

If you know anything about this weird OC15, please

TeKaDe OC15 transistor

TeKaDe 21/30 transistor

Here is a later transistor in a standard TO-9 can marked 21/30. I assume that this is also a GFT21, but an improved later version, with a suffix indicating probably a voltage rating, as listed on the Radiomuseum entry.

If you have data for TeKaDe's semiconductors, or have have some for sale or trade, please


This is apparently a TeKaDe GFT26/8, with the prefix GFT omitted as is often the case. However there are a couple of unusual aspects: firstly the brass-coloured TO-5 can is atypical of TeKaDe, and secondly the suffix /8 seems odd because it usually indicates a maximum voltage, and 8 volts is much too low. Furthermore, a Web search for GFT26 brings up a Thomson power transistor, which is not this one. So, if you have data for this device, please

TeKaDe GFT26/8 transistor

TeKaDe GFT44/15 transistor

Here is a TKD transistor with very poor printing; it is marked GFT44/15B. Radiomuseum states that it is intended as an AM broadcast mixer/oscillator.


This is a power transistor in a TO-66 outline, marked GFT3708/60. According to Radiomuseum this dates from 1956 but that sounds rather early to me. I think 1960 would be more plausible.

TeKaDe GFT3708 transistor

And here is a transistor type GFT4012/30 in a tallish TO-3 can. It is a germanium AF high-power amplifier with maximum values Vce = 30 volts, Ic = 4 amps and Pc = 16 Watts. This shows that TeKaDe were quite advanced in germanium power transistor development.

TeKaDe GFT4012 transistor

TeKaDe XO7001 transistor

This is a TKD transistor marked only 7001. It is in fact an OX7001, which is an out-of-spec GFT20 or GFT21 that was sold in bulk to other vendors who marketed hobbyist kits and devices to the amateur market. I am seeking other such TKD types, or information about them (other than the Radiomuseum entries):

  • OX4000 series eg OX4010
  • OX6000 series eg OX6003
  • OX7000 series eg OX7020

This transistor is marked only HF1. It is another out-of-spec TKD type sold in the hobby/amateur market.

TeKaDe HF1 transistor

I have a few other low-power TKD transistor types. However I have no definitive data for any of them, just the Radiomuseum information plus some characteristic values in the "Discontinued Transistor Data Book". If you can provide data books or sheets for TeKaDe's semiconductors, please contact me!


TeKaDe wanted diodes

TeKaDe made other semiconductor diodes which I am seeking:

  • C10 varicap diode
  • OS32 to OS36 silicon diodes
  • G2 and OY1 germanium diodes







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