Hey everyone,

Is this rectifier selenium?

http://lh5.ggpht.com/_XyPGkTSngb8/SpkUlI-DmXI/AAAAAAAAAKE/uGJl-Lp3ZS8/s640/135-3575_IMG.JPG

Is it a good idea to replace it and could I replace it with a 1N4004 or 1N4006? - that's what I've got on hand.

Sorry, one other question... can someone point me to where they show you how to to do a thumbnail pic please?

Thanks a lot!

the tubular thing is a resistor :D

Not sure about the thing on the left without a better view.

the tubular thing is a resistor :D

Not sure about the thing on the left without a better view.

Thanks... I'm talking about the thing with the red wire - there's a yellow one too. I'm thinking the red is pos - yellow neg.

Not sure.Don't look like the ones I'm used to seeing.Whats the schematic say.Looks kinda like the back side of a pilot lamp socket.It might be one ,very small one.

Not sure.Don't look like the ones I'm used to seeing.Whats the schematic say.Looks kinda like the back side of a pilot lamp socket.It might be one ,very small one.

Hey Avionic, thanks for the reply. Here's another shot...

http://lh3.ggpht.com/_XyPGkTSngb8/SpmT-S2QiaI/AAAAAAAAAK4/qNf7J76-ayM/s640/135-3578_IMG.JPG

The schematic just shows a diode symbol. I don't have a parts list but this is definitely where the diode goes according to the schematic.

Now that's a batch of selenium diodes! BTW, how do you do those thumbnail pics?

Oh, it's got "Bradley Labs, Inc - USA" printed on top.

I'm pretty sure that's a copper oxide rectifier. The "stacking" gives it away.

I'm pretty sure that's a copper oxide rectifier. The "stacking" gives it away.

Thanks electronjohn. Would you leave alone? All I read about is these seleniums going bang and emitted some toxic killer gas. Are these copper oxides OK?

Don't know a heck of a lot about them...they go waaaaay back. I've seen them in bias supplies in some 30s gear. Kinda doubt it would go bad,since it's probably under a very light load. Lift a lead and check it both ways with your VOM & see what you get.

Well, been googling these metal rectifiers and the jist is that they're inefficient and with the selenium over time will generally go bad and emit nasty odors. The coper oxide doesn't seem to give off an odor but it's still pretty inefficient compared to the new silicon diodes.

The metal one I've got works OK but since I'm rebuilding this old tester might as well change the rectifier too.

You might want to leave it be...it's likely the circuit is calibrated for the specific voltage drop developed over a copper oxide rectifier. Just thinkin', y'know.

You might want to leave it be...it's likely the circuit is calibrated for the specific voltage drop developed over a copper oxide rectifier. Just thinkin', y'know.

Good point... I had thought about that and intend to replace the resistor just after the diode to adjust the current to where it was originally.