OA70 diode equivalents ? - UK Vintage Radio Repair and Restoration Discussion Forum

Radio_Dave · 15th Oct 2006, 4:26 pm

The OA70 inside one of the IFT's of my Bush TR82 is open circuit. Are there any other diodes that I could sub it for?

Thanks
David

ukcol · 15th Oct 2006, 4:51 pm

Hi David

An OA91 would do fine if you have one, the important thing is it must be a germanium type, silicon won't do due to the relatively high forward voltage drop.

You could try using the emitter-base junction of an old small-signal germanium transistor.

mickjjo · 15th Oct 2006, 4:57 pm

Hi Dave, The OA70 is listed as a video detector diode, Perhaps Bush had large stocks of them. I think almost any germanium diode would be fine as an AM detector, Try OA79, OA81, OA90, or OA91.

Regards, Mick.

paulsherwin · 15th Oct 2006, 6:50 pm

You will find at least one suitable detector diode in any scrap trannie. As Colin says, most base-emitter junctions of germanium transistors should work too.

A silicon Schottky diode should also work, though I've never actually tried one.

Paul

Sideband · 15th Oct 2006, 7:08 pm

Quote:

Originally Posted by Radio_Dave

The OA70 inside one of the IFT's of my Bush TR82 is open circuit. Are there any other diodes that I could sub it for?

I've had this same problem a couple of years ago in one of the TR82's I repaired for Howard. I used an OA91 with no problems. Almost any Germanium diode will work in this position as long as it will physically fit...even a good old GEX34!

Rich.

15th Oct 2006, 4:26 pm	#1
Radio_Dave Nonode Join Date: Jun 2004 Location: Norwich, Norfolk, UK. Posts: 2,543	OA70 diode equivalents ? The OA70 inside one of the IFT's of my Bush TR82 is open circuit. Are there any other diodes that I could sub it for? Thanks David

15th Oct 2006, 4:51 pm	#2
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: OA70 diode equivalents ? Hi David An OA91 would do fine if you have one, the important thing is it must be a germanium type, silicon won't do due to the relatively high forward voltage drop. You could try using the emitter-base junction of an old small-signal germanium transistor.

15th Oct 2006, 4:57 pm	#3
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: OA70 diode equivalents ? Hi Dave, The OA70 is listed as a video detector diode, Perhaps Bush had large stocks of them. I think almost any germanium diode would be fine as an AM detector, Try OA79, OA81, OA90, or OA91. Regards, Mick. Last edited by Darren-UK; 28th Dec 2007 at 2:13 am. Reason: Excessive use of emoticons.

15th Oct 2006, 6:50 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: OA70 diode equivalents ? You will find at least one suitable detector diode in any scrap trannie. As Colin says, most base-emitter junctions of germanium transistors should work too. A silicon Schottky diode should also work, though I've never actually tried one. Paul