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Specs on old transistors, please?

  • Thread starter Stein-Olav Lund
  • Start date
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Stein-Olav Lund

Jan 1, 1970
0
I have been given some old transistors which I can't find specs on, not
on the net and not in any of the books I have access to.

First is a silicon NPN in a TO-66 case, marked 43A175954P2 (Motorola)


Second is a germanium PNP in a TO-36 case, marked '108'.
This is from an old IBM mainframe computer from early 1960's.

Then another TO-36 Ge PNP, marked 6840-2 (Motorola)

As these Ge power transistors are rare today, I could perhaps use them
as replacements in old equipment I have.
However, I do not know Vce max and Ic max, help is appreciated.


Regards
Stein-Olav Lund
 
With those obscure numbers, I would suggest you test them. If you
increase Vce while monitoring the base to emitter voltage, when the
base voltage reaches the valence voltage that is absolute Vceo for that
temperature. Then using a current limited supply, for germanium I'd say
600-700 uA, increment the Vcb until the current reaches the level found
when testing Vceo. That is usually about 20-50% higher than Vce. It
applies when the transistor base is driven from a low impedance source.

For current, after you have established Vce max, go down to 10V and
start incrementally increasing base current, when you fing the Hfe
roilling off, you are getting close to Ic max.

For Pd you will need to get emperical data on junction temp. You
measure the temp of the case without a heatsink, and plot the base
emitter valence voltage against that, then do it with a heatsink. From
that you extrapolate the die to case thermal resistance. Also remember
Ge transistors limit at 100C not 200. You derate everything twice as
fast.

Ideally, to simplify the math, use a huge capacity heat sink. Perhaps
immerse it in water. As the valence voltage drops due to higher
junction temp, the actual wattage dissipated at the time will yield the
figures.When the valence indicates max junction temp, and the case is
at 25C, you are at the absolute Pd. This is from where you derate
running off a standard JEDEC/JANTX type data sheet.

Another hint: when the Hfe at a given current drops to about 60% or so
of hfe you are about at Ic max.

If you got a sinewave SG, Ft is when gain drops to .707 of DC gain.
Make it easy on yourself and use a resistive load.

I can give a bit more detail, but time prohibits. For comprehensive
details there are textbooks, or even manuals for curve tracers could be
of help.

JURB
 
M

mike

Jan 1, 1970
0
With those obscure numbers, I would suggest you test them. If you
increase Vce while monitoring the base to emitter voltage, when the
base voltage reaches the valence voltage that is absolute Vceo for that
temperature. Then using a current limited supply, for germanium I'd say
600-700 uA, increment the Vcb until the current reaches the level found
when testing Vceo. That is usually about 20-50% higher than Vce. It
applies when the transistor base is driven from a low impedance source.

For current, after you have established Vce max, go down to 10V and
start incrementally increasing base current, when you fing the Hfe
roilling off, you are getting close to Ic max.

For Pd you will need to get emperical data on junction temp. You
measure the temp of the case without a heatsink, and plot the base
emitter valence voltage against that, then do it with a heatsink. From
that you extrapolate the die to case thermal resistance. Also remember
Ge transistors limit at 100C not 200. You derate everything twice as
fast.

Ideally, to simplify the math, use a huge capacity heat sink. Perhaps
immerse it in water. As the valence voltage drops due to higher
junction temp, the actual wattage dissipated at the time will yield the
figures.When the valence indicates max junction temp, and the case is
at 25C, you are at the absolute Pd. This is from where you derate
running off a standard JEDEC/JANTX type data sheet.

Another hint: when the Hfe at a given current drops to about 60% or so
of hfe you are about at Ic max.

If you got a sinewave SG, Ft is when gain drops to .707 of DC gain.
Make it easy on yourself and use a resistive load.

I can give a bit more detail, but time prohibits. For comprehensive
details there are textbooks, or even manuals for curve tracers could be
of help.

JURB

Very interesting.
Could you please define "valence voltage"? Google ain't too smart in
that area.
Thanks, mike

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Valence voltage is that intrinsic voltage drop of a diode, or in this
case, a transistor. It varies inversely with temperature, and is
closely related to the reading you get on your diode scale. Put your
lighter on under the DUT and the voltage drops. In this case the heat
is applied from the outside. The case temperature will be higher than
the junction temp.

If the heat is emitted from the inside, the junction is hotter then the
case. This is from whence we can derive the real figures.

So the .645V you read across a diode is the valence voltage at that
current and temp. When driving the base of a transistor it is ever so
much more complex.

What's more, 0.140 might be a valid forward reading, and in some
devices it's not wise to test them in reverse. Even the 2 volts reverse
might damage a Ge device. Some may even read leaky when they're good.
Germanium transistors are not all that great except for one thing. They
have low loss at lower voltage levels, like in battery powered stuff.
Silicon devices outperform them hands down until we get to that
intrinsic voltage drop. They have made great strides in silicon, but if
the same effort were put into Ge, or even glass Ovonics, what might the
result be ?

[glass ovonics is an anamorphic semiconductor, the technology was
seemingly dropped after it introduction in the 1970s, very important
facets of this technology have found their way into the manufacture of
solar cells]

IIRC, glass ovonics was polarity independant also, and at the time it
was demonstrated (yes it was) engineers were still having alot of fun
having, for the first time, complementary semiconductors.

For about a decade they did, but a nonpolarized semi, not NPN nor PNP I
think would have really put a craw in them. Twenty years before it was
all tubes, well mostly.

Everybody thought in a negative ground sense, one of the most flagrant
dismissals came with the Sony EXR series of RPTVs. It uses a negative
supply for H deflection and as far as I can discern, the yokes are DC
coupled.
 
A

Asimov

Jan 1, 1970
0
"[email protected]" bravely wrote to "All" (05 Oct 05 18:25:32)
--- on the heady topic of "Re: Specs on old transistors, please?"

ZZ> From: [email protected]
ZZ> Xref: core-easynews sci.electronics.repair:344241

ZZ> With those obscure numbers, I would suggest you test them.

Those are likely "house numbers" but I think with a TO66 they might be
similar to AD161 and AD162 complementary Ge audio output transistors.

A*s*i*m*o*v

.... A stereo system is the altar to the god of music.
 
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