SK3018 germanium transistor from a 60's mopar car radio

[dr pepper]

I know someone with a early 60's plymouth, I tried to repair the mopar am/fm radio a while back, the mixer osc transistor is dead, but its a sk3018 4 pin to18 type metal can device.
I tried a couple of alternatives, but with it being germanium and used as a mixer/osc is difficult to replace.
Any ideas on what I could do to sort this old radio out, being the original my mate wants to keep it.
(I thought he'd sold the car and mentioned this on another thread, but apparently not).

 

[Nigel Goodwin]

I know someone with a early 60's plymouth, I tried to repair the mopar am/fm radio a while back, the mixer osc transistor is dead, but its a sk3018 4 pin to18 type metal can device.
I tried a couple of alternatives, but with it being germanium and used as a mixer/osc is difficult to replace.
Any ideas on what I could do to sort this old radio out, being the original my mate wants to keep it.
(I thought he'd sold the car and mentioned this on another thread, but apparently not).

The problem is finding germanium transistors these days - the standard Mullard ones were AF117's, long obsolete, but for a while you could get AF127's to replace them.

The fourth wire is just the screening can, the most common failure with them was a short to the can, and you could almost always restore operation by simply cutting the fourth wire

The number on the original transistor could well be an in-house number, not something that you could ever find.

 

[cowboybob]

Maybe:



Claims to be suitable sub... NPN mixer.

Might need sheilding. And more drive.

 

[dr pepper]

I didnt fancy messing around with the biasing with this, which I'd need to for a silicon.

Didnt know about snipping the can lead, might try that, I did hear you could smack then with a 'driver to temporarily restore operation, that didnt work.

 

[House0Fwax]

I just found this listing on eBay;

**broken link removed**

 

[Nigel Goodwin]

I didnt fancy messing around with the biasing with this, which I'd need to for a silicon.

Didnt know about snipping the can lead, might try that, I did hear you could smack then with a 'driver to temporarily restore operation, that didnt work.

Is it NPN or PNP?, the NTE list above suggests NPN, but from previous experience here it's not very often right

The ones I mentioned above were PNP, as most germanium transistors were.

 

[dr pepper]

The schem shows an npn.

I think of i look hard enough I have some ac127's, ones in a little ally block with a bolthole, though it may take too long to find, I also might have a couple of ocxx devices somewhere the ones with the black painted clear platic case, the ones you used to scrape the paint off and use as light sensors as a kid.

 

[Nigel Goodwin]

The schem shows an npn.

Are you sure it's germanium? - the 1970 Mullard Data Book shows no NPN germanium RF transistors at all - and I don't recall ever seeing one?.

I think of i look hard enough I have some ac127's, ones in a little ally block with a bolthole, though it may take too long to find, I also might have a couple of ocxx devices somewhere the ones with the black painted clear platic case, the ones you used to scrape the paint off and use as light sensors as a kid.

The AC127 is audio only, no ft listed for it, but the later AC187 lists an ft of only 5MHz.

There are numerous NPN silicon RF transistors listed back then though.

 

[dr pepper]

Atually I cant remember how I got to thinking its germanium.
I spose the way to find out would be to pull a good one and measure the vbe with a power supply and resistor

 

[Nigel Goodwin]

Atually I cant remember how I got to thinking its germanium.
I spose the way to find out would be to pull a good one and measure the vbe with a power supply and resistor

Or your multimeter on diode test.

 

[eeprof]

I think I have an sk3018 in my 60 year stock. let me know if you still have the problem.

 

[dr pepper]

I guess that would depend on the number of beertokens required.
Thanks for the offer.

 

[cowboybob]

i think i have an sk3018 in my 60 year stock. Let me know if you still have the problem.

i guess that would depend on the number of beertokens required.

Chortle...

 

[eeprof]

SK 3018 Mopar Auto Radio

1. SK3018 is an NPN high frequency SILICON transistor.
2. It crosses to an NTE/ECG 316 which is readily available.
3. That SK3018 is not original to that MoPar radio --someone has replaced it previously.
Good luck with it.

 

[dr pepper]

I cannot get the nte either, tried that at the time.
All the devices in the set as sk3018, except the o/p devices and they are shown on the parts list on the drawing I have.
To be honest I've spent that much time on this heap of junk I'd rather not return to it.

 

[tvtech]

I cannot get the nte either, tried that at the time.
All the devices in the set as sk3018, except the o/p devices and they are shown on the parts list on the drawing I have.
To be honest I've spent that much time on this heap of junk I'd rather not return to it.

Hi dr pepper

Time is Money. Don't waste time on rubbish/ junk.

Ditch the stuff rather. ...but tell the Customer too. So you are all on the same Page.

You will be surprised at how understanding Customers can be if you tell the truth. You are not wasting their time or money.

Harsh as it might sound....it works. They will return ....to you.

Because they trust you. And not the chancer down the road......

Regards,
tvtech