What Germanium PNP transistor do I use?

You don't.

Germanium transistors were pretty much obsoleted forty years ago, by silicon transistors. There is a far better range of silicon transistors, and generally they have far better specs than germanium transistors.

The only reason you'd use a germanium transistor at this time is if there was a specific reason for using germanium. There are still some things where germanium transistors can be useful, which is why some are still being manufactured, but the average hobbyist wouldn't have need for those uses. And there is no reason to use germanium transistors in a radio.

If you are looking for germanium tranistors because you have a schematic that uses them, and then you can't find the devices specified, it's because the schematic is decades old and you need to drop that schematic and find soemthing more modern, than try to find germanium transistors to use in the schematic.

The reason some of us have germanium transistors lying around is because we accumualted them decades ago, when they were still common. Beyond taht, you'll have to go out of your way to get them.

Michael

The OP might want to preserve originality while repairing an old radio, otherwise I'd select a fairly ordinary silicon PNP type and tweak the bias if necessary.

Hi, Daniel. I've got to assume you're working with an existing radio circuit, probably an older one made in the 1960s when germanium PNPs and negative supplies (positive GND) ruled the earth. Those were the days.

Here's the drill. Find the standard JEDEC 2N number, either in the schematic or printed on the body/case of the transistor. Then go to this link:

$$Search?OpenForm

and type in the manufacturer part number for the transistor. The NTE cross reference will probably work for you. NTE parts are available at many different places, including many TV/radio repair shops. You can also get these online at many places. You can go to their main page:

to find a distributor.

Good luck Chris

That's right, unless it's hobby and there are tons of them in the box. My favorites were AC127 for audio, AF126 up to FM band, and AF239 for the really hot stuff.

Where? Where?

All I've found so far was new old stock so it can't be used in any new design. Ge would be really handy for very low voltage applications such as starter circuitry for a single fuel cell converter.

And that accumulation habit has rescued my old Minolta camera where I really needed a Ge diode. The old OA91 works like a champ after being boxed up for about three decades.

--
Regards, Joerg

http://www.analogconsultants.com

I've repaired several old time transistor portables using germaniums scavaged over the years from all sorts of 60's portable crap. And that relates a lot with how I got my start with this stuff back in the

60's. But I agree that if this is an experimental or kit that the OP needs to find something more current dated unless he's just into that kind of stuff.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794

Michael: Thanks for your education. But I have an old 4-transistor superhet. radio schematic and my kits want to build this radio. So I want to find out what Ge transistors I need. My radio knowledge is severely limited, but I know the first transistor is very different from the last two (a pair) that do the audio output job.

Best! Daniel

Thanks, Chris, for your help. I tried the Web sites. Fantastic! Best! Daniel

** You will have to post that schematic somewhere.

BTW

Why are no transistor numbers on it?

..... Phil

Where will you find the other parts? Loopstick, tuning capacitor, IF transformers and audio transformers?

?Menu=/English/Content/Categories/CatM_95.asp%26Detail=/English/Content/Divisions/Div_95_650.asp

Phil: The only information on the schematic about these transistors are HF andOscillitor, IF, Driver, and Audio Output. Thanks! Dan

"Homer J Simpson"

** I can see those question coming at us like an express train down a tunnel.

Then he will ask us where to buy a soldering iron.

..... Phil

** So you are refusing to post that schem ?

Or explain where it came from ?

....... Phil

*****Oh no, Phil. Not at all. But I have no idea how to post it online. Am I supposed to scan it in first? Or....? I got the schematic from a old dairy kept by my uncle. He passed away years ago. He was an electrician and a radio hobbist. I guess he kep the schematic himself for a long time, or perhaps he once wanted to buid it himslef, but did. Now my kids are interested in building it. Best wishes to you! Dan

** That would help.

Then get a real news account instead of the Google abortion you are using.

Then you can post it on ABSE = " alt.binaries.schematics.electronic"

Or....? I got the schematic from a old dairy kept

** Good thing it was not a plan for a moon rocket......

...... Phil

You cheapest source would be a $5 radio from Wal-Mart.

Hi, Dan. I like the idea of working from the diary to discover what your uncle was thinking. But there are a couple of gotchas here.

First off, many ideas jotted down in notebooks aren't really complete. I know many of mine aren't. He may have been just writing in an idea to fill out later.

Also, an old AM radio design with less than 5 transistors is probably taking a shortcut somewhere. Not necessarily a bad thing, but even if it's a guaranteed working circuit he just copied down, it's probably relying on a trick we'd have to see to evaluate choice of transistors. I'd hate to see you and the kids go to the work of trying to put something together from scratch and have it fail because of some free newsgroup advice. ;-)

As a bonus, layout in RF circuits is pretty important, to prevent unwanted oscillations in the amplifier stages. Working from a schematic only, as a relative newbie you might end up going down a rabbit trail there, too.

Old educational transistor radio kits are still being made which are guaranteed to work and provide a good educational experience. You could do worse than getting the Elenco AM-550TK (5 transistor, no ICs, old-style transistor radio kit with good educational brochure explaining the circuit), building it with the kids, and then raising a glass to the memory of their dad's uncle when they turn it on and it works. Similar in many ways, you get all the parts you need, almost guaranteed success if you have any soldering and assembly skill, and after you're done, you'll understand a lot more about his idea (and possibly where the shortcut is).

Good luck Chris

But otherwise, it's a question like "where do I get a tunnel diode, I want to build this circuit I found in a book or on the internet...". And the poster doesn't realize how old the schematic is, or that tunnel diodes at their best were mostly a novelty (with some real exceptions) and for the hobbyist lasted about a decade (to stretch things a bit).

In order to stick with the circuit, they will have to work really hard to find a tunnel diode, and may pay good money for it. And before that, they really should evaluate why they want to make that circuit. IN most cases, it's because they don't know better (because they want to build something simple, and it certainly is a simple circuit).

I thought people talked about power germaniums still being made and used. The talk would have been in one of the sci.electronics.* newsgroups sometime in the past decade, but that's the best I can provide as a pointer.

Michael