I'm repairing a Technics SA-828 receiver which is in need of 2 pieces of 2OA99 germanium diodes.

The only present subsitute I come across is an NTE device, not my first choice of brand.

Can such a diode be substituted by a schottlkey diode or are there any germanium diodes still produced?

 

hi j,
Look here.
http://www.ebay.com/bhp/germanium-diode
E

 

Thanks E.

Unfortunately, no shipping to Europe.

I did some more checking, a substitute to the 1N34A and the 1N60 would be the CDSH270 (obsolete) and that would substitute to the BAT41. The latter is not a germanium diode, but would it not just do the job as well?

 

hi,
In the UK.
https://www.ebay.co.uk/sch/i.html?_...des+UK.TRS0&_nkw=germanium+diodes+UK&_sacat=0

or

https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=140_141_142&products_id=3041


What is you location.?

 

Netherlands, I could buy from England, no problem.

Still, after having done even some more research, I found out that the difference between OA99 and 2OA99 seems to be that the latter is a matched set of 2 OA99's.

Interesting. What would be the things to check when matching, forward voltage drop? I never noticed very large difference in between diodes of the same model when it comes to this.

 

hi,
For a Receiver, I would ensure that switching speed and inter electrode capacitance is similar to the original.
Most general purpose Ge diodes have the same forward voltage drop.

 

I checked some germanium diodes I had in my parts box, they indeed individually differ a lot on voltage drop! I didn't know that, regular silicon diodes are much more constant.

As for the SA-828, the 2OA99's are part of the power amp board, so no radio function here. But they indeed are present in pairs and now I know they are matched I need to look into that when replacing them.

I'll probably order a bunch of 1N34A's and see if I can match them.

Thanks for the input so far!

 

http://pdf1.alldatasheet.net/datasheet-pdf/view/96792/NIEC/FSD20A90.html.

Hi,
see link for 20A90 DIODES.

 

That seems to be rather overkill

 

The major differences between a germanium diode and a Schottky diode will probably be breakdown voltage and leakage current.
I suspect that neither of these are a problem.

If you post the schematic you will get better answers.

 

They are in this part of the receiver, just before the drivers and the power transistors;

 

I am not sure which diodes you mean. What are their reference numbers?

 

hi RO,
These diodes.
E

 

D615 - D622, 2OA99

D616 and D618 were shorted (same as D615 and D617 in this part of the schematic)

 

Which makes it interesting regarding the matching, would D615 need to be machted with D617 or with D621...

 

D615 - D622, 2OA99
D616 and D618 were shorted (same as D615 and D617 in this part of the schematic)

Both of them? How odd. That requires much thought.

 

Ok, please be my guest