Obsolete JEDEC Designations
This page holds a few additional transistors outlines that are obsolete. Package outlines that use low number JEDEC designations, used by early transistors no longer in production. Because these packages are so old, only the outline drawing is provided. The actual physical dimensions are available but not provided here to reduce server bandwidth.
TO-36 Outline
TO-36 Package Drawing
The TO-36 has four pins; however the pin designated by the call-out G is an alignment pins, and is isolated from both the case and the other pins. The alignment pin is only used for mechanical alignment of the part during installation. The case is considered a heat sink; although any metal package with no electrical connection might be considered a heat sink. The symbol J indicates that the terminal is threaded per 10-32 UNF-2A, but also has a solder lug at the end of the terminal. Because of the large size of the component the over-all size of 1.250 inches is shown in the diagram. A representative part using this package style would be a 2N1358, which was a high-power PNP germanium transistor.
TO-41 Outline
TO-41 Package Drawing
The TO-41 transistor outline is another odd shaped package. Although the case does use the common diamond shaped outline, used by the widely used TO-3 package. This package also has two leads, with the third terminal being the case of the device. As shown in the drawing the Base and Emitter of the transistor use the leads, while the transistor Collector connects to the metal case. The difference here is that both the Base and Emitter terminals have solder connections, when most other packages of this style have straight pins.
Many heat sinks designed for the diamond package only have small cut-outs to accept the straight pins coming off the device. These large solder tabs would never fit through the standard holes; however some heat sinks basically remove all the material under the device, leaving only mounting hole to attach to.
The intended purpose of the solder tabs is obvious when chassis mounting is considered. Many times these packages are bolted to the outside of a metal chassis, which than allows the entire chassis to act as a heat sink. Because the TO-41 would be mounted off the printed wiring board, wires are used to interconnect the board to the device. The solder tabs are used to secure the wires to the semiconductor device.
A PNP 2N1120 Germanium switching transistor is a component that used this package.
TO-53 Outline
The TO-53 is another chassis or panel mount device. NPN general purpose transistors 2N389 and 2N424, among others use the TO-53 package [drawing shown to the left]. This package differs from the standard diamond pattern, by being some what square shape. The other noticeable difference is that the TO-53 uses solder hooks instead of pins.
The change in lead style again relates to the fact that many times these device are mounted to a metal chassis or panel and are some distance away from the circuit on the printed circuit board. The solder hooks allow wires to be mechanically secured to the posts and be soldered for the electrical connection. The Solder Hook is used , or was used on a number of other electrical components to include relays and transformers.
This device has three individual component leads; a Base, Emitter and Collector. In this case, and in many others, the collector is also connected to the case. Of course there are packages that only have two leads and use the case as the Collector terminal.
TO-57 Outline
The TO-57 component package also has a threaded bolt [6-32 UNC-2A], but unlike the TO-36 this bolt is only used to secure the device to another surface. The Collector has a lead and is also connected to the case. A 2N1047 transistor uses this package. The base, large diameter [D] is 0.460 inches. |  TO-57 Package Drawing |
Package Obsolescence
These packages are of course obsolete, and use inactive JEDEC designations. However many years ago these were common packages. This page primarily covers odd-shaped out-dated package styles. The companion page to this one covers more main stream packages, but that are also out dated; Obsolete JEDEC Transistor Cases. Any transistor part numbers provided as an example are of course also obsolete. but might be available at a hamfest.
The physical dimensions are again omitted for these clearly obsolete packages.
