The company IPRS ('Întreprinderea de piese radio și semiconductori' which translates as 'enterprise radio parts and semiconductors') located in Băneasa borough of Bucharest in Romania, founded in 1962, produced electronic components and electrical and electronic equipment including germanium transistors. These sometimes bear their logo of a Greek 'beta' symbol, but are often unbranded.

I am grateful to a correspondent, Raul in Romania, who has sent me early types and information about them, including a downloadable 1983 Romanian electronics book: 'Agenda radioelectronistului' by Nicolae George Drăgulănescu. This provides data for the following IPRS germanium transistor types (plus many silicon types that I don't list here):

The AC types use TO-1A cans; those with the suffix K have the same block heatsink that is found on Telefunken types. The EFT types, the low-power ones also in TO-1A cans, appear to be a second-source equivalent to devices in the SF.T series originated by the French company CSF. The early semiconductor industry in France is obscure in its own right, so how a Romanian company established such a commercial arrangement is unclear to me.

I also possess an earlier Romanian data book: 'Catalog de Dispozitive Semiconductoare' by Veronica Vătăşescu and Şerban Epure, 1966. It lists the following EFT types as equivalent to SF.T series with the same numbers:

There is also interesting information and images of devices (germanium and silicon discretes, plus integrated circuits) on the Romanian wikipedia, and here is that page translated by Google.


AC180K transistor

Here is an AC180K. It uses the TO-1A can inside a metal block heatsink. It is a germanium PNP medium-power audio-frequency amplifier. You can see the printed 'beta' β of IPRS.

AD130 transistor

And here are two power types: AD130 in the larger TO-3 outline and AD155 in the smaller TO-66 outline. Both are listed in 'Agenda radioelectronistului'. Again, both have the printed 'beta' β of IPRS.


EFT83b transistor

I believe that this transistor type EFT83B was made by IPRS although it does not have a 'beta' on it. It is a PNP germanium alloy transistor but am unsure whether it is for AF, IF or even RF applications. It is commonly available on eBay, but it does not seem to have an SF.T original and I can find no technical data for it, although 'Agenda radioelectronistului' does list a type EFT83S.

If you can clarify this, please

EFT321 transistor

Here are three transistors: types EFT321, EFT322 and EFT352. Unlike my EFT83B transistors, these are painted black. I bought them from someone who said that they were made by CSF, however I think that unlikely. They are all germanium PNP alloy-junction low-power types and are listed in 'Catalog de Dispozitive Semiconductoare'.

EFT213 transistor

Here is an EFT213 PNP germanium power transistor. Like many Romanian types it has a coloured paint dot on it. This is actually an indicator of the device's gain, according to the following scheme:

  • Red ............ 15-35
  • Orange ....... 25-45
  • Yellow ....... 35-55
  • Green ......... 45-65
  • Blue ........... 55-80
  • Violet ......... 75-100
  • White ......... 85-180

This is the same colour-coding used on early Bulgarian transistors.


DC1 diode

I have few IPRS diodes. This image shows three types, none with a β on them:

  • DC1 is a bias stabilisation diode. I don't know whether it is germanium or silicon. However 'Agenda radioelectronistului' lists DC2 and DC4 and from their voltage drop they must be silicon.
  • I believe that DR370 is a rectifier diode. I don't know whether it is germanium or silicon.
  • DZ309 is a Zener diode. It is listed in 'Catalog de Dispozitive Semiconductoare'. It must be silicon.

The book 'Agenda radioelectronistului' lists many diodes made by IPRS, including many part numbers familiar from Western manufacturers, for example AA types, OA types and 1N types. More interesting from a historic viewpoint are true Romanian types: the EFR and EFD series plus several series starting with D. The book seems to show that the low-power types were axial and identified by three coloured stripes.

If you know where I might obtain more IPRS diodes, please