251D diode for Selenium rectifier replacement?

[Donald_S]

I will be replacing the Selenium rectifiers on a couple of German radios. From what I've read on the web, most people recommend 1N4007 diodes in a bridge configuration with bypass caps across each diode. The 1N4007 is rated for 1A forward current (continuous) with a peak reverse voltage of 1000V. I do not have enough 1N4007s for replacement of two selenium rectifiers, but I do have a bunch of 251D diodes. I believe these are Silicon diodes (like the 1N4007) and are rated 2.5A and 1000V. Unfortunately, I have not been able to locate the data sheet for this diode and I am therefore not sure if they can be used instead of the 1N4007s. The current rating is certainly higher, but without a datasheet I do not know if the 2.5A rating is for continuous current or just peak current. Also, I do not know if there are any other diode parameters that need to be looked into when using them for replacing selenium rectifiers. Any suggestions / clarifications will be welcomed.

 

[electroking]

A diode with a 2.5 A rating is definitely acceptable in the power supply of
a tube radio, and one with 1.0 A would also be fine. The highest current
in a diode in such an application occurs at startup, when first charging
the filter capacitors. If the design of the power supply guarantees this
does not exceed the rating of the diodes, everything should be fine.

Most German radios I know (the example I have in mind is a Blaupunkt
Verona from 1960) use silicon diodes from the factory, not selenium
rectifiers. Are you sure you have selenium units in your radio?

Good luck.

 

[Donald_S]

Most German radios I know (the example I have in mind is a Blaupunkt
Verona from 1960) use silicon diodes from the factory, not selenium
rectifiers. Are you sure you have selenium units in your radio?

Good luck.

I am pretty sure that both the Saba 300 automatic 9T and the Telefunken Opus 7 have Selenium rectifiers...