Electronic Schematics (alt.binaries.schematics.electronic) A place to show and share your electronics schematic drawings.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 800
Default Testing Germanium transistors.

What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that nulls
out the leakage before taking a gain measurement, the leakage is read off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an oscillator
with its output clipped by an inverse parallel pair of diodes and measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC conditions.

Any comments/suggestions welcome.

TIA.


  #2   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 257
Default Testing Germanium transistors.

Well, you can easily

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


"ian field" wrote in message
...
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls out the leakage before taking a gain measurement, the leakage is
read off the calibrated null pot, but I'm wondering whether it might be
better to measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator with its output clipped by an inverse parallel pair of diodes
and measuring the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.



  #3   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 257
Default Testing Germanium transistors.

Well, you can easily measure Icbo with a resistor and voltage source.
Change base voltage and see where it goes. Set up a common emitter
amplifier circuit. That sort of thing.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

"ian field" wrote in message
...
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls out the leakage before taking a gain measurement, the leakage is
read off the calibrated null pot, but I'm wondering whether it might be
better to measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator with its output clipped by an inverse parallel pair of diodes
and measuring the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.





  #4   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 488
Default Testing Germanium transistors.

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that nulls
out the leakage before taking a gain measurement, the leakage is read off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an oscillator
with its output clipped by an inverse parallel pair of diodes and measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.
  #5   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 2,221
Default Testing Germanium transistors.

On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that nulls
out the leakage before taking a gain measurement, the leakage is read off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an oscillator
with its output clipped by an inverse parallel pair of diodes and measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.


I can't even remember what the expected gain ranges were for Germanium
;-)

But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Help save the environment!
Please dispose of socialism properly!


  #6   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 800
Default Testing Germanium transistors.


"Jim Thompson" /Snicker
wrote in message ...
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls
out the leakage before taking a gain measurement, the leakage is read
off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator
with its output clipped by an inverse parallel pair of diodes and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.


I can't even remember what the expected gain ranges were for Germanium
;-)

But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?


Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias and emitter
resistor, or the large nfb collector to base resistor with no emitter
resistor.

The worse the stage is affected by leakage, the better I can check leakage
by measuring the drop on the collector resistor (I think?!).


  #7   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 2,221
Default Testing Germanium transistors.

On Thu, 17 Dec 2009 15:48:49 -0000, "ian field"
wrote:


"Jim Thompson" /Snicker
wrote in message ...
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls
out the leakage before taking a gain measurement, the leakage is read
off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator
with its output clipped by an inverse parallel pair of diodes and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.


I can't even remember what the expected gain ranges were for Germanium
;-)

But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?


Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias and emitter
resistor,


That's actually pretty good if adequate drop is taken across the
emitter resistor. 0.25V or more is best for Silicon... I can't
remember for Germanium ;-)

or the large nfb collector to base resistor with no emitter
resistor.


Or no nfb... just straight to rail... commonly know as "suicide bias".
:-(


The worse the stage is affected by leakage, the better I can check leakage
by measuring the drop on the collector resistor (I think?!).


Sure.

(For analysis, simply add a current labeled ICBO from collector to
base, then calculate what your bias network does to improve that.)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Help save the environment!
Please dispose of socialism properly!
  #8   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 12,924
Default Testing Germanium transistors.


Jim Thompson wrote:

On Thu, 17 Dec 2009 15:48:49 -0000, "ian field"
wrote:


"Jim Thompson" /Snicker
wrote in message ...
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls
out the leakage before taking a gain measurement, the leakage is read
off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator
with its output clipped by an inverse parallel pair of diodes and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.

I can't even remember what the expected gain ranges were for Germanium
;-)

But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?


Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias and emitter
resistor,


That's actually pretty good if adequate drop is taken across the
emitter resistor. 0.25V or more is best for Silicon... I can't
remember for Germanium ;-)

or the large nfb collector to base resistor with no emitter
resistor.


Or no nfb... just straight to rail... commonly know as "suicide bias".
:-(


The worse the stage is affected by leakage, the better I can check leakage
by measuring the drop on the collector resistor (I think?!).


Sure.

(For analysis, simply add a current labeled ICBO from collector to
base, then calculate what your bias network does to improve that.)



The ARRL handbooks had a transistor tester in a lot of editions, but
the only one I have at hand is the '55 edition. I'll look later today
or tomorrow for a mid '60s edition.


--
Offworld checks no longer accepted!
  #9   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 2,221
Default Testing Germanium transistors.

On Thu, 17 Dec 2009 11:39:35 -0500, "Michael A. Terrell"
wrote:


Jim Thompson wrote:

On Thu, 17 Dec 2009 15:48:49 -0000, "ian field"
wrote:


"Jim Thompson" /Snicker
wrote in message ...
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls
out the leakage before taking a gain measurement, the leakage is read
off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator
with its output clipped by an inverse parallel pair of diodes and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.

I can't even remember what the expected gain ranges were for Germanium
;-)

But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?

Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias and emitter
resistor,


That's actually pretty good if adequate drop is taken across the
emitter resistor. 0.25V or more is best for Silicon... I can't
remember for Germanium ;-)

or the large nfb collector to base resistor with no emitter
resistor.


Or no nfb... just straight to rail... commonly know as "suicide bias".
:-(


The worse the stage is affected by leakage, the better I can check leakage
by measuring the drop on the collector resistor (I think?!).


Sure.

(For analysis, simply add a current labeled ICBO from collector to
base, then calculate what your bias network does to improve that.)



The ARRL handbooks had a transistor tester in a lot of editions, but
the only one I have at hand is the '55 edition. I'll look later today
or tomorrow for a mid '60s edition.


Thanks for the reminder, I may actually have a drawing around here
myself, for such a tester.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Help save the environment!
Please dispose of socialism properly!
  #10   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 488
Default Testing Germanium transistors.

ian field wrote:
"Jim Thompson" /Snicker
wrote in message ...
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls
out the leakage before taking a gain measurement, the leakage is read
off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator
with its output clipped by an inverse parallel pair of diodes and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.

I can't even remember what the expected gain ranges were for Germanium
;-)

But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?


Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias and emitter
resistor, or the large nfb collector to base resistor with no emitter
resistor.

The worse the stage is affected by leakage, the better I can check leakage
by measuring the drop on the collector resistor (I think?!).



Best stability design is to use voltage divider base bias and emitter
resistor.
Measure two leakages: 1) short base to emitter, measure collector
current as a function of voltage, and 2) measure base current (meter
acts like a short to emitter) as a function of collector voltage.


  #11   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 28
Default Testing Germanium transistors.

On Thu, 17 Dec 2009 11:39:35 -0500, "Michael A. Terrell"
wrote:



The ARRL handbooks had a transistor tester in a lot of editions, but
the only one I have at hand is the '55 edition. I'll look later today
or tomorrow for a mid '60s edition.


The '61 ARRL HB, no joy. The '78 Orr Handbook was for silicon, as was
the '82 ARRL.

HOWEVER, the '62 GE Transistor Manual had a circuit for a transistor
tester. I'll give you the words for an NPN. Do the appropriate
inversion for the PNP.

6 volt battery, push button gain switch, 0-3 mA meter with Zin 760
ohms.

Leakage: Collector directly to +6v. Base open. Emitter directly to
+ Meter lead. - meter lead to - 6v through a 680 ohm resistor

Gain: Directly as Leakage but base to + 6v through a 200K resistor.

Notes:

Battery check: 560 ohm resistor between emitter and collector. Meter
reads full scale or battery is below minimums.

Leakage: Insert transistor into socket. Meter reads leakage.

Gain: Press gain switch button. Gain is meter reading minus leakage
reading.

Best I could do.

Jim
  #12   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 800
Default Testing Germanium transistors.



HOWEVER, the '62 GE Transistor Manual had a circuit for a transistor
tester. I'll give you the words for an NPN. Do the appropriate
inversion for the PNP.

6 volt battery, push button gain switch, 0-3 mA meter with Zin 760
ohms.

Leakage: Collector directly to +6v. Base open. Emitter directly to
+ Meter lead. - meter lead to - 6v through a 680 ohm resistor

Gain: Directly as Leakage but base to + 6v through a 200K resistor.

Notes:

Battery check: 560 ohm resistor between emitter and collector. Meter
reads full scale or battery is below minimums.

Leakage: Insert transistor into socket. Meter reads leakage.

Gain: Press gain switch button. Gain is meter reading minus leakage
reading.

Best I could do.

Jim




There was a circuit published in a very old copy of The Radio Constructor
that nulls out the leakage before measuring gain, but I was wondering about
an AC gain tester, I could maybe calculate leakage from volt drop on the
collector resistor or include a cheap mc meter in the collector load.








Attached Thumbnails
Testing Germanium transistors.-page2-jpg  Testing Germanium transistors.-page3-jpg  Testing Germanium transistors.-page1-jpg  
  #13   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 83
Default Testing Germanium transistors.

Jim Thompson wrote:
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:


ian field wrote:

What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that nulls
out the leakage before taking a gain measurement, the leakage is read off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an oscillator
with its output clipped by an inverse parallel pair of diodes and measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC conditions.

Any comments/suggestions welcome.

TIA.



Once upon a time, a long time ago, RS under their Micronta brand made
a tester that bypassed the DC gain problem by the use of a transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain readout.
Maybe this is of some help.



I can't even remember what the expected gain ranges were for Germanium
;-)


Rubber ruler time: the CK722 was the greatest thing since sliced
bread when it came out. It had a huge* gain for such a small
device, something like 20 or 30 as I recall! I think I still
have my first one.

* = (rubber ruler values of "huge" :-)

Ed


But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?

...Jim Thompson

  #14   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 367
Default Testing Germanium transistors.



"Michael A. Terrell" wrote in message
news

Jim Thompson wrote:

On Thu, 17 Dec 2009 15:48:49 -0000, "ian field"
wrote:


"Jim Thompson"
/Snicker
wrote in message ...
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium
transistors?

Even the peak atlas transistor analyser reads leakage current as
gain
current and the DMMs I have are completely useless at testing
germanium
transistors. Somewhere I have a schematic for a transistor
tester that
nulls
out the leakage before taking a gain measurement, the leakage is
read
off
the calibrated null pot, but I'm wondering whether it might be
better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with
an
oscillator
with its output clipped by an inverse parallel pair of diodes
and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be
added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use
that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta
brand made
a tester that bypassed the DC gain problem by the use of a
transformer
for AC feedback, and a pot on the feedback secondary for feeding
the
signal to the base.
Pot setting gave an indication of the gain (at the collector
current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain
readout.
Maybe this is of some help.

I can't even remember what the expected gain ranges were for
Germanium
;-)

But I thoroughly remember several weeks spent in the classroom
(1960)
studying biasing techniques.

Anyone have a curve tracer?

Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias and
emitter
resistor,


That's actually pretty good if adequate drop is taken across the
emitter resistor. 0.25V or more is best for Silicon... I can't
remember for Germanium ;-)

or the large nfb collector to base resistor with no emitter
resistor.


Or no nfb... just straight to rail... commonly know as "suicide
bias".
:-(


The worse the stage is affected by leakage, the better I can check
leakage
by measuring the drop on the collector resistor (I think?!).


Sure.

(For analysis, simply add a current labeled ICBO from collector to
base, then calculate what your bias network does to improve that.)



The ARRL handbooks had a transistor tester in a lot of editions, but
the only one I have at hand is the '55 edition. I'll look later today
or tomorrow for a mid '60s edition.



I have, I think, a '65 HB, plus some old GE transistor manuals.
I'll flip thru them and see.

Cheers



  #15   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 800
Default Testing Germanium transistors.


"Martin Riddle" wrote in message
...


"Michael A. Terrell" wrote in message
news

Jim Thompson wrote:

On Thu, 17 Dec 2009 15:48:49 -0000, "ian field"
wrote:


"Jim Thompson" /Snicker
wrote in message ...
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as
gain
current and the DMMs I have are completely useless at testing
germanium
transistors. Somewhere I have a schematic for a transistor tester
that
nulls
out the leakage before taking a gain measurement, the leakage is
read
off
the calibrated null pot, but I'm wondering whether it might be
better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator
with its output clipped by an inverse parallel pair of diodes and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be
added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that
would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta brand
made
a tester that bypassed the DC gain problem by the use of a
transformer
for AC feedback, and a pot on the feedback secondary for feeding the
signal to the base.
Pot setting gave an indication of the gain (at the collector
current
set by the DC biasing; think that was a common bace bias scheme).
They used an inverse log taper pot to get a more linear gain
readout.
Maybe this is of some help.

I can't even remember what the expected gain ranges were for
Germanium
;-)

But I thoroughly remember several weeks spent in the classroom (1960)
studying biasing techniques.

Anyone have a curve tracer?

Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias and
emitter
resistor,

That's actually pretty good if adequate drop is taken across the
emitter resistor. 0.25V or more is best for Silicon... I can't
remember for Germanium ;-)

or the large nfb collector to base resistor with no emitter
resistor.

Or no nfb... just straight to rail... commonly know as "suicide bias".
:-(


The worse the stage is affected by leakage, the better I can check
leakage
by measuring the drop on the collector resistor (I think?!).


Sure.

(For analysis, simply add a current labeled ICBO from collector to
base, then calculate what your bias network does to improve that.)



The ARRL handbooks had a transistor tester in a lot of editions, but
the only one I have at hand is the '55 edition. I'll look later today
or tomorrow for a mid '60s edition.



I have, I think, a '65 HB, plus some old GE transistor manuals.
I'll flip thru them and see.

Cheers


Please-2^(1/12) scan and post.




  #16   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 367
Default Testing Germanium transistors.



"RST Engineering" wrote in message
...
On Thu, 17 Dec 2009 11:39:35 -0500, "Michael A. Terrell"
wrote:



The ARRL handbooks had a transistor tester in a lot of editions,
but
the only one I have at hand is the '55 edition. I'll look later today
or tomorrow for a mid '60s edition.


The '61 ARRL HB, no joy. The '78 Orr Handbook was for silicon, as was
the '82 ARRL.

HOWEVER, the '62 GE Transistor Manual had a circuit for a transistor
tester. I'll give you the words for an NPN. Do the appropriate
inversion for the PNP.

6 volt battery, push button gain switch, 0-3 mA meter with Zin 760
ohms.

Leakage: Collector directly to +6v. Base open. Emitter directly to
+ Meter lead. - meter lead to - 6v through a 680 ohm resistor

Gain: Directly as Leakage but base to + 6v through a 200K resistor.

Notes:

Battery check: 560 ohm resistor between emitter and collector. Meter
reads full scale or battery is below minimums.

Leakage: Insert transistor into socket. Meter reads leakage.

Gain: Press gain switch button. Gain is meter reading minus leakage
reading.

Best I could do.

Jim


Here's the 1962 page of the GE Transistor manual....






Attached Thumbnails
Testing Germanium transistors.-ge-transistor-test-set-1962-jpg  
  #17   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 367
Default Testing Germanium transistors.



"ian field" wrote in message
...

"Martin Riddle" wrote in message
...


"Michael A. Terrell" wrote in message
news

Jim Thompson wrote:

On Thu, 17 Dec 2009 15:48:49 -0000, "ian field"
wrote:


"Jim Thompson"
/Snicker
wrote in message
.. .
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium
transistors?

Even the peak atlas transistor analyser reads leakage current
as
gain
current and the DMMs I have are completely useless at testing
germanium
transistors. Somewhere I have a schematic for a transistor
tester
that
nulls
out the leakage before taking a gain measurement, the leakage
is
read
off
the calibrated null pot, but I'm wondering whether it might be
better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with
an
oscillator
with its output clipped by an inverse parallel pair of diodes
and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can
be
added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use
that
would
betray the leakage figure by simple voltage measurement under
DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta
brand
made
a tester that bypassed the DC gain problem by the use of a
transformer
for AC feedback, and a pot on the feedback secondary for feeding
the
signal to the base.
Pot setting gave an indication of the gain (at the collector
current
set by the DC biasing; think that was a common bace bias
scheme).
They used an inverse log taper pot to get a more linear gain
readout.
Maybe this is of some help.

I can't even remember what the expected gain ranges were for
Germanium
;-)

But I thoroughly remember several weeks spent in the classroom
(1960)
studying biasing techniques.

Anyone have a curve tracer?

Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias
and
emitter
resistor,

That's actually pretty good if adequate drop is taken across the
emitter resistor. 0.25V or more is best for Silicon... I can't
remember for Germanium ;-)

or the large nfb collector to base resistor with no emitter
resistor.

Or no nfb... just straight to rail... commonly know as "suicide
bias".
:-(


The worse the stage is affected by leakage, the better I can check
leakage
by measuring the drop on the collector resistor (I think?!).


Sure.

(For analysis, simply add a current labeled ICBO from collector to
base, then calculate what your bias network does to improve that.)


The ARRL handbooks had a transistor tester in a lot of editions,
but
the only one I have at hand is the '55 edition. I'll look later
today
or tomorrow for a mid '60s edition.



I have, I think, a '65 HB, plus some old GE transistor manuals.
I'll flip thru them and see.

Cheers


Please-2^(1/12) scan and post.


Nope the ARRL handbook was '61.

But I do have the '62 transistor manual that has a very good section on
measurements for different configurations.

Nothing specific to Germaniums.

Here's a page from the transistor measurement chapter. I'll scan the
chapter into a pdf on monday.
Hfe for Germaniums ranged from 20-200.

Cheers





Attached Thumbnails
Testing Germanium transistors.-dc-gain-measurment-1962-ge-transistor-manual-jpg  
  #18   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 2,221
Default Testing Germanium transistors.

On Wed, 16 Dec 2009 14:06:30 -0000, "ian field"
wrote:

What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that nulls
out the leakage before taking a gain measurement, the leakage is read off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an oscillator
with its output clipped by an inverse parallel pair of diodes and measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC conditions.

Any comments/suggestions welcome.

TIA.


Don't know if this is any good...

http://www.electronickits.com/kit/co...eas/dt-100.pdf

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Help save the environment!
Please dispose of socialism properly!
  #19   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 800
Default Testing Germanium transistors.


"Jim Thompson" /Snicker
wrote in message ...
On Wed, 16 Dec 2009 14:06:30 -0000, "ian field"
wrote:

What's the best approach to testing salvaged germanium transistors?

Even the peak atlas transistor analyser reads leakage current as gain
current and the DMMs I have are completely useless at testing germanium
transistors. Somewhere I have a schematic for a transistor tester that
nulls
out the leakage before taking a gain measurement, the leakage is read off
the calibrated null pot, but I'm wondering whether it might be better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with an
oscillator
with its output clipped by an inverse parallel pair of diodes and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can be added to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use that would
betray the leakage figure by simple voltage measurement under DC
conditions.

Any comments/suggestions welcome.

TIA.


Don't know if this is any good...

http://www.electronickits.com/kit/co...eas/dt-100.pdf


Looks worthy of study - thanks.


  #20   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 182
Default Testing Germanium transistors.

On Fri, 18 Dec 2009 21:34:14 -0500, "Martin Riddle" wrote:



"ian field" wrote in message
...

"Martin Riddle" wrote in message
...


"Michael A. Terrell" wrote in message
news
Jim Thompson wrote:

On Thu, 17 Dec 2009 15:48:49 -0000, "ian field"
wrote:


"Jim Thompson"
/Snicker
wrote in message
.. .
On Thu, 17 Dec 2009 02:27:23 -0800, Robert Baer
wrote:

ian field wrote:
What's the best approach to testing salvaged germanium
transistors?

Even the peak atlas transistor analyser reads leakage current
as
gain
current and the DMMs I have are completely useless at testing
germanium
transistors. Somewhere I have a schematic for a transistor
tester
that
nulls
out the leakage before taking a gain measurement, the leakage
is
read
off
the calibrated null pot, but I'm wondering whether it might be
better to
measure the AC gain?

What I'm thinking of is driving the transistor under test with
an
oscillator
with its output clipped by an inverse parallel pair of diodes
and
measuring
the rectified output of the TUT to calculate gain.

One particular advantage I'm thinking of, is an amplifier can
be
added
to
evaluate how much hiss the TUT contributes.

The clever bit would be deciding what biasing circuit to use
that
would
betray the leakage figure by simple voltage measurement under
DC
conditions.

Any comments/suggestions welcome.

TIA.


Once upon a time, a long time ago, RS under their Micronta
brand
made
a tester that bypassed the DC gain problem by the use of a
transformer
for AC feedback, and a pot on the feedback secondary for feeding
the
signal to the base.
Pot setting gave an indication of the gain (at the collector
current
set by the DC biasing; think that was a common bace bias
scheme).
They used an inverse log taper pot to get a more linear gain
readout.
Maybe this is of some help.

I can't even remember what the expected gain ranges were for
Germanium
;-)

But I thoroughly remember several weeks spent in the classroom
(1960)
studying biasing techniques.

Anyone have a curve tracer?

Which variant of common emitter is most susceptible to leakage?

The 2 choices I'm thinking of are the voltage divider base bias
and
emitter
resistor,

That's actually pretty good if adequate drop is taken across the
emitter resistor. 0.25V or more is best for Silicon... I can't
remember for Germanium ;-)

or the large nfb collector to base resistor with no emitter
resistor.

Or no nfb... just straight to rail... commonly know as "suicide
bias".
:-(


The worse the stage is affected by leakage, the better I can check
leakage
by measuring the drop on the collector resistor (I think?!).


Sure.

(For analysis, simply add a current labeled ICBO from collector to
base, then calculate what your bias network does to improve that.)


The ARRL handbooks had a transistor tester in a lot of editions,
but
the only one I have at hand is the '55 edition. I'll look later
today
or tomorrow for a mid '60s edition.



I have, I think, a '65 HB, plus some old GE transistor manuals.
I'll flip thru them and see.

Cheers


Please-2^(1/12) scan and post.


Nope the ARRL handbook was '61.

But I do have the '62 transistor manual that has a very good section on
measurements for different configurations.

Nothing specific to Germaniums.

Here's a page from the transistor measurement chapter. I'll scan the
chapter into a pdf on monday.
Hfe for Germaniums ranged from 20-200.

Cheers


1962, i think that was previous to my favorite, 7th edition. Maybe '65 or '66?
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tektronix Germanium Tunnel Diode. ian field Electronic Schematics 14 April 20th 08 04:36 PM
Uses for 150-300 amp transistors? Leon Heller Metalworking 9 February 15th 05 11:15 PM
Laws requiring portable appliance testing and electrical installation testing if any? Z UK diy 9 June 14th 04 12:00 PM
Germanium XSTR cross reference Shoreline Electronics Electronics Repair 1 February 15th 04 02:35 PM
germanium diode/Microwave oven Don ßailey Electronics Repair 2 August 21st 03 11:08 PM


All times are GMT +1. The time now is 09:07 AM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"