Re: 2N2222A vs 2N3904 sourcing
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Jerry
Since the FT is what we need to know for transistor swaps, it might be possible to
make an oscillator circuit that tunes across the predicted FT value.? Point where the
oscillator stops or will not start could be a good indication of FT for a particular device.
Motorola AN-139 is interesting: Is there any other way to actually measure FT of BJT devices?
Arv _._
On Thu, Sep 13, 2018 at 3:15 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: Kees,
Otherwise unobtainable plastic 2n2222A's available for pennies on ebay?
In this particular case, I'm not so sure about the first part in "Trust, but verify".?
But certainly possible, the recipe has been out there for 50 years.
Ebay might be worth a shot if you want a bunch.
For small quantities on prototypes, I'd just give Mouser their $2 for item?610-2N2222A
If you really want a bunch, then Mouser item?583-2N2222A from Rectron is $0.21 each at quantity 10000.
All 2n2222A's on Mouser have metal cans, which should dissipate more than anything plastic.
Especially if you put some sort of heatsink on them.
Or give them a liquid nitrogen bath.
There are parts that are better than the 2n2222A's, especially if interested in operating above 20m.
Search for 2n5109 in this forum for discussion of that and other parts.
Maybe also search for BS170 too, Mouser price of $0.44 for one, $0.12 each for 100.?
Jerry
?
On Thu, Sep 13, 2018 at 01:18 PM, Kees T wrote:
I think enough work has been done to say the 3 sets of 2N3904 transistors should be replaced with 3 sets of 2N2222A transistors. The 2N2222A is a great transistor but has been around a while and most retailers have classified them as "obsolete" and dumped the plastic versions to surplus dealers to sell. They still sell the TO-18 metal can versions at quite high prices because the military still needs them to repair "stuff". Many surplus dealers now have the plastic 2N2222A parts available for pennies on places like ebay.
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