Identifiy the Diode-ish device

Question

I've got a component (4 of them), from a Bruel & Kjaer 2803 Two Channel Microphone Power supply -- side note, anyone have a circuit diagram for it, would make life easier to trouble shoot.

The component comes from the 28V pre-amp power supply subsystem, and the four of them are kind of connected in a bridge-rectifier type configuration, but not quite.

It has the marking "ER 21" on it, and a symbol that looks similar to

I'm looking to replace the components, so I need to know what I could replace them with

Answer 1

Have you checked if they are actually diodes? I've taken apart old electronics, and seen devices in a very similar package that were just diodes.

In the early days of silicon diodes, they came in a lot of odd packages. It wouldn't surprise me if that was actually a diode. Considering that this is an older piece of equipment (googling Bruel & Kjaer 2803 gets me documents from 1967), it's probably just a early silicon diode.

I would bet that the tapered end is very likely the cathode.

Try using the diode-check option on your multi-meter. They're probably just simple silicon rectifiers. If so, you can replace them with inexpensive 1N4001 diodes, or similar.

Answer 2

Perhaps the symbol you mentioned is supposed to indicate a Schottky diode or a Zener diode.

(I tried to upload the symbols from http://en.wikipedia.org/wiki/diode ; I don't know why they don't show up here).

I've seen a few tantalum capacitors with an axial package/case that looks similar to that -- a cylinder with a chamfer on one end:

(picture from http://www.digikey.com/us/en/ph/Vishay/TANTALEX.html )

Answer 3

I've seen these in 1970s Radford (UK) solid state hifi amps and preamps. They were rectifier diodes when I encountered them, but I would bung them on a curve tracer to double check they aren't Zeners. But then I have a curve tracer :-)

Or else leave them be.