Old Gernanium Transistor Repair

It could be a lot of things. You need to find a way to test which.

Usually two for output, two for audio amps = 4.

Actually 7. Some radios had non working transistors added to bring the count up.

You might need to alter the bias on each transistor you replace.

snipped-for-privacy@att.net wrote in news:1163387574.804150.266160 @h54g2000cwb.googlegroups.com:

Try over on alt.antiques.radio+phono... they'll enjoy hearing about your germanium transistors.

I don't know. There has been debate in the past over there about what's relevant to the newsgroup, and some have felt transistors aren't old enough.

Michael

Perfectly easy to manage with three - one driver only.

--
*Could it be that "I do " is the longest sentence? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Some of them think that Atwater Kent radios are too new for that group. Ignore them, there are a number of transistor radio collectors in that group. I have most of the "Sams Transistor Radio Manuals" in my collection:

The Sams index is available online.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

By "noisy" do you mean there is lots of background hiss, or do you mean the sound is rough and distorted?

No. The radio was designed to work with germanium transistors. Every stage you change over to silicon will need to be rebiased, retuned, and reneutralized. Not an easy job.

I'd start with replacing the electrolytics. Quite likely they're at about 20% of their original selves. Weak electrolytics can make the radio motorboat, or sound tinny and noisy.

Since warmer=drier, I might look for paper tubular caps. When moist, they leak badly.

But in those days more transistors = more sales. I used to fix such things.

Replacing parts at random on electronics makes not one bit of sense. There are hundreds of components and hundreds of connections, any one of which may be to do with it. Trying to repair a radio by replacing geraniums with silicon makes even less sense. Germanium trs are still sold new as well as used.

If you dont know what youre doing, leave it alone.

NT

Paper capacitors? Transistor radios use electrolytic and mylar film instead of paper, but the electrolytics were poor quality, and they don't age very well. The capacitors in tuned circuits are either mica, ceramic or polystyrene.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Lytic caps are easily tested by piggybacking. Just clip a similar value cap on, no need for any soldering or cutting. But really its farily pointless unless you do some fault finding first.

NT

Get a can Of "Cold Spray" when it is working good, gently spray each transistor to find which one is causing the trouble. Then replace it with a new germanium transistor.

Unless they are leaky, then "Piggybacking" is a waste of time. I have an ESR meter, and a digital capacitor meter. On the other hand, I would probably just replace all the old electrolytics first, then look for other problems. It usually only takes a couple dollars worth of new caps, and they should be replaced if you plan to actually use the radio.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

How many gangs on the tuning cap? Many of the 8 transistor radios had an RF stage - if there are 3 gangs on the tuning cap that is a giveaway

David

snipped-for-privacy@att.net wrote:

Yes, lots of background hiss and roar at low temperature. At 80 degrees F, it's not too bad, but at 55 degrees it whistles and squeals and the weak stations are lost.

I'm not sure the design is the best. They used a couple resistors to set the bias on the output stage, and when the battery voltage falls a volt or so, the output has some crossover distortion. I fixed that problem with a couple diodes in place of a resistor so the bias current stays above zero as the battery voltage falls. I can now drop the supply voltage a couple volts with no crossover distortion.

Yes, that could be a problem, but the AGC seems to work well, so that capacitor must be ok.

-Bill

Hi Bill...

I haven't read the whole thread, so if I'm repeating anyone else please accept my apologies.

Why not consider operating it in a warmish room, and spraying local components one at a time (with a few minutes break in between) with "freeze in a can" (whatever they call it in your part of the world) until you find the component that causes it to act up.

And just for the heck of it, my bet's on a resistor.

Take care.

Ken

There are about about 50 components. This is little portable radio about the size of 2 packs of cigarettes (5.25 by 3 by 1.25). I like it because it's easy to carry around and sounds better than the smaller versions.

sense.

Well, if I leave it alone, I can only use it on hot days. I'm trying to figure out a way I can use it on hot and COLD days?

Maybe you have a suggestion to overcome the temperature problems?

-Bill

It's just a little pocket size radio (5 X 3 X 1.5) with 2 sections for the tuning cap.It has the usual four RF coils and input and output audio transformers. But that only requires 6 transistors, and there are

8 used. I suppose I can trace out the connections to try and figure out what the extra 2 transistors do.

The real way to fix it is with a signal tracer and signal generator. Isolate to a section and fault find there.