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#1
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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
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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
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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
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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
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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
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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
Posted to alt.binaries.schematics.electronic
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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
Posted to alt.binaries.schematics.electronic
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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
Posted to alt.binaries.schematics.electronic
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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
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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
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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
Posted to alt.binaries.schematics.electronic
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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. |
#13
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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
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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
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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
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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.... |
#17
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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 |
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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
Posted to alt.binaries.schematics.electronic
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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
Posted to alt.binaries.schematics.electronic
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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? |
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