[Milsurplus] [MRCA] mystery diode

[Bob Camp]

Hi

Ideally folks would still be making a wide range of germanium parts in all sorts of packages. That hasn’t been true for a long time. We also have pretty much burned through whatever was on distributor shelves. Yes there are a very few parts still made, but their are always exceptions. 

The closest thing that *is* made in a variety of packages, voltage ratings, and current ratings are  schottky diodes. You can’t *quite* get as low a forward voltage as a germanium. Some designs are a lot closer than others. They are dirt cheap and you have a lot of choices. 

Every manual I can easily find either has a useless schematic or none at all. Without seeing the “tiny” part there’s no way to point to a specific item to try. Still, I’d bet there’s something out there. 

Worst case: The tuning meter still works, it just doesn’t peak at quite the same point on the dial. 

Bob

> On Sep 15, 2025, at 8:39 AM, mstangelo--- via Milsurplus <milsurplus at mailman.qth.net> wrote:
> 
> Too early... schottky.
>> On 09/15/2025 8:31 AM EDT mstangelo at comcast.net wrote:
>>  
>>  
>> Ray,
>>  
>> I would try a Schotyky diode.
>>  
>> Mike N2MS 
>>  
>>  
>>> On 09/14/2025 9:04 PM EDT Ray Fantini via MRCA <mrca at mailman.qth.net> wrote:
>>>  
>>>  
>>> Ok, so I have a very early AN/PRC-74 on the bench that has a shorted PD9047 diode (CR-15) that's used to develop the voltage for the tuning meter. the dam thing is very small and somehow don't think a 1N34 will take its place.
>>> AI tells me that's a way obsolete part number and beyond its ability to come up with a replacement, anyone have any ideas? the tuning meter is somewhat important on the 74
>>> This particular radio is serial number 606 and the PA deck is serial number 8! has strong output and in all other ways good.
>>> you can see the circuit on page 186, figure 7-11 in the manual.
>>>  
>>> Ray F/KA3EKH
>>>  
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