[Milsurplus] Early silicon transistor failures

[Bob kb8tq]

Hi

If we’re talking about radios, HFE probably is not the number to focus on. Gain bandwidth would likely be the bigger issue. Not enough and you have no signal. To much and the stage goes into oscillation. The gotcha here is that the spec sheet numbers may not exist or if they do exist they may be misleading. Still, a better area to focus on since HFE and Ft (however you measure it) are not directly linked to each other. 

Bob

> On Dec 22, 2023, at 10:17 AM, mstangelo at comcast.net wrote:
> 
> Jim,
> 
> I saw this add today in Electronic Goldmine. Have you tried 2N3903 the lower gain version of the popular 2N3904?
> 
> <https://theelectronicgoldmine.com/products/g26902?mc_cid=a7184dc10f&mc_eid=9999d432a7>
> 
> 73 Mike N2MS
> 
>> On 12/21/2023 11:45 AM EST Jim Whartenby via Milsurplus <milsurplus at mailman.qth.net> wrote:
>> 
>> 
>> Ray
>> The TC-1 found on eBay, see enclosure. They can be had for under $20.00 with free shipping. According to YouTube, there are clones out there so examples with the test leads and charger cord appear to be original units. YMMV
>> 
>> I am working on KWT-6 SMO modules, mostly scrapped circuit boards from SMOs with mechanical problems. I guess that they were stored outside since they have frozen bearings which I don't care to replace. You can't save everything although I try my best!
>> 
>> I have been successful using a TI house numbered device found at a Missouri Hamfest years ago. They are TO-18 devices that are just useable with their 1/2 inch long leads. They range in current gain from 20 to 80. So far, devices in the 20 to high 30s range seem to work well. It is hard to find modern transistors with HFEs that low. I have ordered 200 each of the 2N4400 devices (datasheet enclosed) as a backup and will try sorting them with the TC-1 for HFE and emitter current.
>> Jim
> 
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