Versuche es mit einem kurzschlussfesten Labornetzgerät, das wenigstens 3A liefert. Darf auch mehr sein, aber Du solltest den Strom begrenzen können. Spannung von 30V zwischen Transistorgehäuse und BCE reicht ggf. schon.

dl8aap.koch-carsten.de/2016/01/transistor-ausbrennen/

Oder diese Methode:
markhennessy.co.uk/articles/vi…rs.htm#dealing_with_af11x

Zitat:

Remove the transistor from the radio. Measure the resistance
between screen and the other electrodes - you might find that at least
one of them will exhibit a low resistance (10Ω or less), or you
might find that any resistance is pretty high - a few kΩ or more.
In some cases, you might not find any leakage at all. Even if this is the
case, you've taken the effort to remove the transistor, so carry on with
the procedure - treating them can fix a fault, even if there appears to
be no leakage to speak of.

Connect together the collector, base and emitter leads. Use a dab of
solder to be absolutely sure they are firmly connected. If you forget to
join them, then there is a risk of damage to the
junction.

Find a decent electrolytic capacitor - this will be charged up by a
bench power supply, and will ensure the maximum energy is delivered
directly into the transistor. I'd recommend using at least 100µF
for this. The voltage rating obviously depends on what you have
available.

Connect a bench power supply to the capacitor. At this stage, set the
output to 0 volts. This power supply remains connected throughout the
whole procedure, and will top up the capacitor if it loses charge.
The power supply should be at least 30V - more if you have it. The higher
the voltage, the further the electricity will be able to jump, so the
more whiskers will be caught by the discharge. Some people use lower
voltages - such as 9V from a PP3 - but I feel that the higher, the
better

Solder one end of the capacitor to the 3 twisted electrodes. Bend the
leads so that the screen lead is just a short distance away from the
other end of the capacitor.

Wind up the voltage of the power supply. Take great care to ensure you
don't touch both ends of the capacitor at the same time - espeically if
you are using higher voltages. Bring the end of the capacitor and the
screen lead together, and watch and listen for a small spark as the
energy is discharged into the transistor. If you are especially lucky,
you might even see the bottom end of the transistor light up (the base
plate is glass).

Wind down the DC power supply to zero volts. You've probably sorted it
at this stage, but I do an extra step (I think I invented this, for what
that's worth!).

Solder the screen lead to the capacitor, and wind up the voltage
again. At this stage, we're not expecting any current to be flowing, as
we've already zapped the whiskers. But, these can be tricky little
things, so we'll hunt out any that might be hiding just out of reach...
Very carefully, sharply hit the body of the transistor from
several different directions. I hold the transistor just a couple of
millimetres above a metal bench vice, and hit it from above with a large
screwdriver - this gives the transistor a double-impact from two sides.
Rotate and do it again. After 30 or so seconds of this, you can be
confident that there is nothing waiting to "land" after just a few weeks
of operation. Sometimes, you do see the PSU output dip slightly as the
capacitor quickly recharges after an impact, which is reassuring
confirmation of something actually happening during this part of the
process.

Finally, check for leakage between the screen and other electrodes.
Re-fit the transistor to the radio (I never bother testing it first),
taking care to neatly straighten out the leads and re-forming them to
fit back into the PCB. Re-fit any sleeving that was used, and be extra
careful about putting it back correctly (many manufacturers omitted the
silk-screen from their PCBs). Once all the transistors have been done.
the radio should burst back into life - although of course you might have
to search for other age-related faults like faulty electrolytic
capacitors. If needed, basic DC voltage measurements will confirm that
the transistors are acting as transistors.

Foto:
markhennessy.co.uk/articles/af11x_zapping.jpg


Gruss,
Reinhard

Das Erste Mal, dass ich von einer Methode lese, Whisker zu beseitigen- liest sich, wie Bildröhren regenerieren. Waren von dieser "Krankheit" nur Kleinleistungs- GE-Typen betroffen, oder auch größere Transistoren wie AL, oder AD....?
Gruß... --Hans--

Lieber Hans 2
Lies mal dort
radiomuseum.org/forum/graetz_d…032_transistorersatz.html

radiomuseum.org/forum/af117_and_tin_whiskers.html

nepp.nasa.gov/whisker/index.html

hans

Moin Hans,

gibt es schon konkrete Berichte, dass dieses Problem mit den neuen Loten verstärkt oder früher auftritt ? Das wäre ja schon ein heftiger Punkt. Mir war bekannt, dass man in der Medizintechnik wohl nicht auf bleifrei umstellen musste (ist das immer noch so ?), aber was Du da schreibst hätte ja massive Auswirkungen auf alle möglichen sicherheitsrelevanten Schaltungen ...

Besten Gruss,

Michael

Lieber Michael.
Ich bin da heute zuweit weg vom Fenster.
Wisker gibt es auch bei ALU. Eine Passivierung loest dort das Problem.
Auesere Loetstellen kann man gegen Feuchte versiegeln.
Die minichips sicher nicht zu 100%. Weis es aber nicht. .
Die US.Army hat das schon 1940 als "Tropenfest" gemacht. Zinnpest nicht Wisker, waren sicher eher der Grund dazu.
decoder

Anlage:
Die (NSF) jetzt THEMIK hat Rs und Cs auf Prints verwendet, deren Vorverzinnung 0.000001 zuviel Blei enthielt. Leider ist die Zeitung weg! .
Im Browser eingeben:
bing.com/search?q=Blei++in+Lei…en+l+&pc=MOZI&form=MOZSBR

Danke Hans -- man sieht mal wieder, wie subtil manche Dinge sein können ... und dann generelle Bestimmungen schnell nach hinten losgehen können. Zinnpest ist ja noch mit niedrigen Temperaturen verbunden, also sicher in der Raumfahrt ein Punkt, den man genau beachten muss.

Besten Gruss,

Michael

Die einfachste Methode ist es die schönen alten Geräte nicht im Keller verrotten zu lassen, bei regelmäßiger Nutzung werden die Wisker von selber weggeschweißt.
So wie man Mechaniken immer wieder bewegen lassen muß muß man Elektrik/Elektronik immer wieder wirken lassen.
Die schönste Art ist die ständige oder zumindestens regelmäßige Benutzung.