• These voltages are not a problem for most any transistor. In order of importance: collector current, DC current gain and AC current gain at the frequency of
Message 1 of 15 , Jun 2, 2005
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These voltages are not a problem for most any transistor. In order of
importance: collector current, DC current gain and AC current gain at
the frequency of interest.

An emitter voltage of 1.2 volts implies there is some kind of
resistance between the emitter and ground. Not a problem.

You base voltage of 1.4 volts with an emitter voltage of 1.2 volts
means the transistor will never turn on. A 0.2V base-emitter voltage
is probably too low for most any silicon transistor. The 2N2222 turns
on at about 0.55V - see datasheet figure 4
http://www.fairchildsemi.com/ds/PN/PN2222A.pdf

So, what are you trying to drive (voltage and current), how much
current gain do you need (is the base current available limited in
some way)? What frequency are you using? How much AC current gain do
you need?

While you are grabbing small signal datasheets, get the 2N3903,
2N3904, 2N3905 and 2N3905.

For power related stuff, 2N3055. But, watch out, DC current gain is
lousy at higher currents. This means you need more base current and
that complicates the design.

--- In Electronics_101@yahoogroups.com, "berrysmountain"
<berrysmountain@y...> wrote:
> Which NPN transistors currently available at retail electronics
stores
> can accept +6 volts on the collector, +1.2 volts on the emitter, and
> +1.4 volts on the base?
> How do I identify such a transistor before I purchase them?
> What are the model numbers?
> Will just about any general purpose transistor handle these voltages?
> Thanks.
• ... From: berrysmountain To: Sent: Friday, June 03, 2005 4:11 AM Subject: [Electronics_101]
Message 2 of 15 , Jun 2, 2005
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----- Original Message -----
From: "berrysmountain" <berrysmountain@...>
To: <Electronics_101@yahoogroups.com>
Sent: Friday, June 03, 2005 4:11 AM
Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION

> Which NPN transistors currently available at retail electronics stores
> can accept +6 volts on the collector, +1.2 volts on the emitter, and
> +1.4 volts on the base?
> How do I identify such a transistor before I purchase them?
> What are the model numbers?
> Will just about any general purpose transistor handle these voltages?

Virtually any device will be OK, provided it will take the current you are
designing for. I'd just use a 2N3904.

You seem to have got the base and emitter voltages wrong for normal use -
when the transistor is biased correctly there should be a 0.6 V difference
between the base and emitter.

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller
• The transistors I am attempting to replace are on an old electronic organ I am repairing. The voltages stated are as listed in the spec sheets for the organ. I
Message 3 of 15 , Jun 3, 2005
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The transistors I am attempting to replace are on an old electronic
organ I am repairing. The voltages stated are as listed in the spec
sheets for the organ. I am attempting to replace vintage transistors
with new ones and I am looking for new replacements that would be
equivalent to the old transistors.
Any suggestions for replacing vintage with modern?

--- In Electronics_101@yahoogroups.com, "Leon Heller"
<leon.heller@d...> wrote:
> ----- Original Message -----
> From: "berrysmountain" <berrysmountain@y...>
> To: <Electronics_101@yahoogroups.com>
> Sent: Friday, June 03, 2005 4:11 AM
> Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
>
>
> > Which NPN transistors currently available at retail electronics stores
> > can accept +6 volts on the collector, +1.2 volts on the emitter, and
> > +1.4 volts on the base?
> > How do I identify such a transistor before I purchase them?
> > What are the model numbers?
> > Will just about any general purpose transistor handle these voltages?
>
> Virtually any device will be OK, provided it will take the current
you are
> designing for. I'd just use a 2N3904.
>
> You seem to have got the base and emitter voltages wrong for normal
use -
> when the transistor is biased correctly there should be a 0.6 V
difference
> between the base and emitter.
>
> Leon
> --
> Leon Heller, G1HSM
> http://www.geocities.com/leon_heller
• Then the transistors may be germanium rather than silicon. This is going to be a problem. The physics of the devices are not at all the same. You can not
Message 4 of 15 , Jun 3, 2005
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Then the transistors may be germanium rather than silicon. This is
going to be a problem. The physics of the devices are not at all
the same. You can not substitute one for the other and have much
success.

You can find some sources of germanium transistors with Google. Is
there no part number on the transistor?

It would be something like 2Nxxx - probably a 3 digit number.

--- In Electronics_101@yahoogroups.com, "berrysmountain"
<berrysmountain@y...> wrote:
> The transistors I am attempting to replace are on an old electronic
> organ I am repairing. The voltages stated are as listed in the spec
> sheets for the organ. I am attempting to replace vintage
transistors
> with new ones and I am looking for new replacements that would be
> equivalent to the old transistors.
> Any suggestions for replacing vintage with modern?
>
>
> --- In Electronics_101@yahoogroups.com, "Leon Heller"
> <leon.heller@d...> wrote:
> > ----- Original Message -----
> > From: "berrysmountain" <berrysmountain@y...>
> > To: <Electronics_101@yahoogroups.com>
> > Sent: Friday, June 03, 2005 4:11 AM
> > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
> >
> >
> > > Which NPN transistors currently available at retail
electronics stores
> > > can accept +6 volts on the collector, +1.2 volts on the
emitter, and
> > > +1.4 volts on the base?
> > > How do I identify such a transistor before I purchase them?
> > > What are the model numbers?
> > > Will just about any general purpose transistor handle these
voltages?
> >
> > Virtually any device will be OK, provided it will take the
current
> you are
> > designing for. I'd just use a 2N3904.
> >
> > You seem to have got the base and emitter voltages wrong for
normal
> use -
> > when the transistor is biased correctly there should be a 0.6 V
> difference
> > between the base and emitter.
> >
> > Leon
> > --
> > Leon Heller, G1HSM
> > http://www.geocities.com/leon_heller
• Germanium it may be. The part number is SGS IW 9787. The two transistors I am trying to replace are on a small divider circuit board. I have removed this small
Message 5 of 15 , Jun 3, 2005
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Germanium it may be.
The part number is SGS IW 9787.
The two transistors I am trying to replace are on a small divider
circuit board. I have removed this small board from the organ. I have
the schematic for the divider circuit board. What if I build the
left by the old divider board? Could new transistors be used?

--- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@p...>
wrote:
>
> Then the transistors may be germanium rather than silicon. This is
> going to be a problem. The physics of the devices are not at all
> the same. You can not substitute one for the other and have much
> success.
>
> You can find some sources of germanium transistors with Google. Is
> there no part number on the transistor?
>
> It would be something like 2Nxxx - probably a 3 digit number.
>
> --- In Electronics_101@yahoogroups.com, "berrysmountain"
> <berrysmountain@y...> wrote:
> > The transistors I am attempting to replace are on an old
electronic
> > organ I am repairing. The voltages stated are as listed in the
spec
> > sheets for the organ. I am attempting to replace vintage
> transistors
> > with new ones and I am looking for new replacements that would be
> > equivalent to the old transistors.
> > Any suggestions for replacing vintage with modern?
> >
> >
> > --- In Electronics_101@yahoogroups.com, "Leon Heller"
> > <leon.heller@d...> wrote:
> > > ----- Original Message -----
> > > From: "berrysmountain" <berrysmountain@y...>
> > > To: <Electronics_101@yahoogroups.com>
> > > Sent: Friday, June 03, 2005 4:11 AM
> > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
> > >
> > >
> > > > Which NPN transistors currently available at retail
> electronics stores
> > > > can accept +6 volts on the collector, +1.2 volts on the
> emitter, and
> > > > +1.4 volts on the base?
> > > > How do I identify such a transistor before I purchase them?
> > > > What are the model numbers?
> > > > Will just about any general purpose transistor handle these
> voltages?
> > >
> > > Virtually any device will be OK, provided it will take the
> current
> > you are
> > > designing for. I'd just use a 2N3904.
> > >
> > > You seem to have got the base and emitter voltages wrong for
> normal
> > use -
> > > when the transistor is biased correctly there should be a 0.6 V
> > difference
> > > between the base and emitter.
> > >
> > > Leon
> > > --
> > > Leon Heller, G1HSM
> > > http://www.geocities.com/leon_heller
• All the SGS IWxxxx I know, are silicon transistor. I think you can try with some 2N3904 or similar. The divider circuit should not be too critical. Bye.
Message 6 of 15 , Jun 3, 2005
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All the SGS IWxxxx I know, are silicon transistor. I think you can try
with some 2N3904 or similar. The divider circuit should not be too critical.

Bye.
Giuliano
----- Original Message -----
Sent: Friday, June 03, 2005 4:30 PM
Subject: [Electronics_101] Re: TRANSISTOR VOLTAGE QUESTION

Germanium it may be.
The part number is SGS IW 9787.
The two transistors I am trying to replace are on a small divider
circuit board. I have removed this small board from the organ. I have
the schematic for the divider circuit board. What if I build the
left by the old divider board? Could new transistors be used?
• I agree, Giuliano. Thanks. ... try ... critical. ... have
Message 7 of 15 , Jun 3, 2005
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I agree, Giuliano.
Thanks.

--- In Electronics_101@yahoogroups.com, "Giuliani" <julcat@t...>
wrote:
> All the SGS IWxxxx I know, are silicon transistor. I think you can
try
> with some 2N3904 or similar. The divider circuit should not be too
critical.
>
> Bye.
> Giuliano
> ----- Original Message -----
> From: berrysmountain
> To: Electronics_101@yahoogroups.com
> Sent: Friday, June 03, 2005 4:30 PM
> Subject: [Electronics_101] Re: TRANSISTOR VOLTAGE QUESTION
>
>
> Germanium it may be.
> The part number is SGS IW 9787.
> The two transistors I am trying to replace are on a small divider
> circuit board. I have removed this small board from the organ. I
have
> the schematic for the divider circuit board. What if I build the
> circuit on a breadboard and solder that breadboard into the space
> left by the old divider board? Could new transistors be used?
• In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time, berrysmountain@yahoo.com writes: What if I build the circuit on a breadboard and solder that
Message 8 of 15 , Jun 3, 2005
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In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time, berrysmountain@... writes:
What if I build the
left by the old divider board? Could new transistors be used?
It's not whether the transistors are "new" or "old".  The older ones were quite probably made with germanium metal, and the "junction drop" in that is about 0.2 Volt.  Newer transistors are generally silicon, and the junction drop in that is about 0.6 volts.  This difference CAN make a difference in audio circuits, etc.

For irrelevant reasons, I'd NEVER work on an electronic "organ" unless it were a matter of [my!] life or death!  But if I were forced at gun-point, I'd ponder using a modern CMOS IC as a flip-flop.  WOULD require knowing some "working voltages" of many points, before beginning, of course.  GOOD LUCK!            Jan Rowland
• ... I would think that pretty many would handle this, unless you re buying some of those really cheap bargain bag assortments or something. The only ones I
Message 9 of 15 , Jun 3, 2005
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On Thursday 02 June 2005 11:11 pm, berrysmountain wrote:
> Which NPN transistors currently available at retail electronics stores
> can accept +6 volts on the collector, +1.2 volts on the emitter, and
> +1.4 volts on the base?
> How do I identify such a transistor before I purchase them?
> What are the model numbers?
> Will just about any general purpose transistor handle these voltages?
> Thanks.

I would think that pretty many would handle this, unless you're buying some
of those really cheap bargain bag assortments or something. The only ones I
recall that tend to have really low breakdown voltages are ones designed to
handle really high frequencies too.

That's one consideration. You also need to figure on how much collector
current you need it to be able to pass, And how much power it needs to be
able to handle, which is not quite the same thing. And finally, how much
gain you need.
• ... What s the number on the original parts? The comments about needing 0.6V of voltage difference between base and emitter do NOT apply if the original part
Message 10 of 15 , Jun 3, 2005
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On Friday 03 June 2005 08:09 am, berrysmountain wrote:
> The transistors I am attempting to replace are on an old electronic
> organ I am repairing. The voltages stated are as listed in the spec
> sheets for the organ. I am attempting to replace vintage transistors
> with new ones and I am looking for new replacements that would be
> equivalent to the old transistors.
> Any suggestions for replacing vintage with modern?

What's the number on the original parts?

The comments about needing 0.6V of voltage difference between base and emitter
do NOT apply if the original part is germanium! In that case 0.2V is pretty
near normal...

You may even be able to find that original number out there. Let us know what
it is and I'll see what turns up.

> --- In Electronics_101@yahoogroups.com, "Leon Heller"
>
> <leon.heller@d...> wrote:
> > ----- Original Message -----
> > From: "berrysmountain" <berrysmountain@y...>
> > To: <Electronics_101@yahoogroups.com>
> > Sent: Friday, June 03, 2005 4:11 AM
> > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
> >
> > > Which NPN transistors currently available at retail electronics stores
> > > can accept +6 volts on the collector, +1.2 volts on the emitter, and
> > > +1.4 volts on the base?
> > > How do I identify such a transistor before I purchase them?
> > > What are the model numbers?
> > > Will just about any general purpose transistor handle these voltages?
> >
> > Virtually any device will be OK, provided it will take the current
>
> you are
>
> > designing for. I'd just use a 2N3904.
> >
> > You seem to have got the base and emitter voltages wrong for normal
>
> use -
>
> > when the transistor is biased correctly there should be a 0.6 V
>
> difference
>
> > between the base and emitter.
> >
> > Leon
> > --
> > Leon Heller, G1HSM
> > http://www.geocities.com/leon_heller
>
>
>
>
• ... Sure you can, in some circuits. :-) ... Or two letters followed by some digits, if it s a European number, or 2S followed by A or B and some digits,
Message 11 of 15 , Jun 3, 2005
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On Friday 03 June 2005 08:22 am, rtstofer wrote:
> Then the transistors may be germanium rather than silicon. This is
> going to be a problem. The physics of the devices are not at all
> the same. You can not substitute one for the other and have much
> success.

Sure you can, in some circuits. :-)

> You can find some sources of germanium transistors with Google. Is
> there no part number on the transistor?
>
> It would be something like 2Nxxx - probably a 3 digit number.

Or two letters followed by some digits, if it's a European number, or 2S
followed by A or B and some digits, if it uses the Japanese numbering
system, or... :-)

That's why I've become an "information packrat" these past couple of years.

> --- In Electronics_101@yahoogroups.com, "berrysmountain"
>
> <berrysmountain@y...> wrote:
> > The transistors I am attempting to replace are on an old electronic
> > organ I am repairing. The voltages stated are as listed in the spec
> > sheets for the organ. I am attempting to replace vintage
>
> transistors
>
> > with new ones and I am looking for new replacements that would be
> > equivalent to the old transistors.
> > Any suggestions for replacing vintage with modern?
> >
> >
> > --- In Electronics_101@yahoogroups.com, "Leon Heller"
> >
> > <leon.heller@d...> wrote:
> > > ----- Original Message -----
> > > From: "berrysmountain" <berrysmountain@y...>
> > > To: <Electronics_101@yahoogroups.com>
> > > Sent: Friday, June 03, 2005 4:11 AM
> > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
> > >
> > > > Which NPN transistors currently available at retail
>
> electronics stores
>
> > > > can accept +6 volts on the collector, +1.2 volts on the
>
> emitter, and
>
> > > > +1.4 volts on the base?
> > > > How do I identify such a transistor before I purchase them?
> > > > What are the model numbers?
> > > > Will just about any general purpose transistor handle these
>
> voltages?
>
> > > Virtually any device will be OK, provided it will take the
>
> current
>
> > you are
> >
> > > designing for. I'd just use a 2N3904.
> > >
> > > You seem to have got the base and emitter voltages wrong for
>
> normal
>
> > use -
> >
> > > when the transistor is biased correctly there should be a 0.6 V
> >
> > difference
> >
> > > between the base and emitter.
> > >
> > > Leon
> > > --
> > > Leon Heller, G1HSM
> > > http://www.geocities.com/leon_heller
>
>
>
>
• ... Searching under that number didn t find me much, but changing that I to a 1 got me to this page: http://www.organservice.com/lowrey/991Parts.htm and
Message 12 of 15 , Jun 3, 2005
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On Friday 03 June 2005 10:30 am, berrysmountain wrote:
> Germanium it may be.
> The part number is SGS IW 9787.

Searching under that number didn't find me much, but changing that "I" to a

and searching within the page got me to this line:

991-011312-000 Transistor: 1W9787 NPN - Use 991-010462-000 0.80

and that one they're saying to use gets us to this line:

991-010462-000 Transistor: 2N2925, NPN 0.80

which is a _silicon_ transistor. You might get away with it in this
application, it's a pretty non-critical circuit.

I believe that "0.80" is probably their price, which seems pretty reasonable.

> The two transistors I am trying to replace are on a small divider
> circuit board. I have removed this small board from the organ. I have
> the schematic for the divider circuit board. What if I build the
> circuit on a breadboard and solder that breadboard into the space
> left by the old divider board? Could new transistors be used?

Yep, maybe...

It probably wouldn't hurt anything to try.

> --- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@p...>
>
> wrote:
> > Then the transistors may be germanium rather than silicon. This is
> > going to be a problem. The physics of the devices are not at all
> > the same. You can not substitute one for the other and have much
> > success.
> >
> > You can find some sources of germanium transistors with Google. Is
> > there no part number on the transistor?
> >
> > It would be something like 2Nxxx - probably a 3 digit number.
> >
> > --- In Electronics_101@yahoogroups.com, "berrysmountain"
> >
> > <berrysmountain@y...> wrote:
> > > The transistors I am attempting to replace are on an old
>
> electronic
>
> > > organ I am repairing. The voltages stated are as listed in the
>
> spec
>
> > > sheets for the organ. I am attempting to replace vintage
> >
> > transistors
> >
> > > with new ones and I am looking for new replacements that would be
> > > equivalent to the old transistors.
> > > Any suggestions for replacing vintage with modern?
> > >
> > >
> > > --- In Electronics_101@yahoogroups.com, "Leon Heller"
> > >
> > > <leon.heller@d...> wrote:
> > > > ----- Original Message -----
> > > > From: "berrysmountain" <berrysmountain@y...>
> > > > To: <Electronics_101@yahoogroups.com>
> > > > Sent: Friday, June 03, 2005 4:11 AM
> > > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
> > > >
> > > > > Which NPN transistors currently available at retail
> >
> > electronics stores
> >
> > > > > can accept +6 volts on the collector, +1.2 volts on the
> >
> > emitter, and
> >
> > > > > +1.4 volts on the base?
> > > > > How do I identify such a transistor before I purchase them?
> > > > > What are the model numbers?
> > > > > Will just about any general purpose transistor handle these
> >
> > voltages?
> >
> > > > Virtually any device will be OK, provided it will take the
> >
> > current
> >
> > > you are
> > >
> > > > designing for. I'd just use a 2N3904.
> > > >
> > > > You seem to have got the base and emitter voltages wrong for
> >
> > normal
> >
> > > use -
> > >
> > > > when the transistor is biased correctly there should be a 0.6 V
> > >
> > > difference
> > >
> > > > between the base and emitter.
> > > >
> > > > Leon
> > > > --
> > > > Leon Heller, G1HSM
> > > > http://www.geocities.com/leon_heller
>
>
>
>
• ... Yeah, where the actual linear operation of the part is concerned. But this divider circuit he s talking about doesn t sound like that at all, and I
Message 13 of 15 , Jun 3, 2005
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On Friday 03 June 2005 03:34 pm, JanRwl@... wrote:
> In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time,
> berrysmountain@... writes:
>
> What if I build the
> circuit on a breadboard and solder that breadboard into the space
> left by the old divider board? Could new transistors be used?
>
> It's not whether the transistors are "new" or "old". The older ones were
> quite probably made with germanium metal, and the "junction drop" in that
> is about 0.2 Volt. Newer transistors are generally silicon, and the
> junction drop in that is about 0.6 volts. This difference CAN make a
> difference in audio circuits, etc.

Yeah, where the actual linear operation of the part is concerned. But this
divider circuit he's talking about doesn't sound like that at all, and I
don't think it's gonna be a problem there.

> For irrelevant reasons, I'd NEVER work on an electronic "organ" unless it
> were a matter of [my!] life or death! But if I were forced at gun-point,
> I'd ponder using a modern CMOS IC as a flip-flop.

Not me!

> WOULD require knowing some "working voltages" of many points, before
> beginning, of course. GOOD LUCK! Jan Rowland

I think this is the one he was talking about earlier on where only six volts
was present, though it isn't clear to me whether this is the actual measured
collector voltage or the power supply voltage.
• Thanks, everyone for your thoughts and advice. The numbers printed on the transistors are: SGS 1W 9787 4640 (the 1 might be an I ). The transistor has a black
Message 14 of 15 , Jun 3, 2005
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The numbers printed on the transistors are:
SGS 1W 9787 4640 (the 1 might be an "I").
The transistor has a black top and gray sides. The numbers are
printed in white on the gray sides. The transistor looks more like a
tiny smudge pot rather than like a shiney tin can. It doesn't look at
all like some of the newer ones with flat black sides.

Thanks for the search and the location of the
"2N2925, NPN 0.80" information on organservice.com

--- In Electronics_101@yahoogroups.com, "Roy J. Tellason"
<rtellason@b...> wrote:
> On Friday 03 June 2005 03:34 pm, JanRwl@A... wrote:
> > In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time,
> > berrysmountain@y... writes:
> >
> > What if I build the
> > circuit on a breadboard and solder that breadboard into the space
> > left by the old divider board? Could new transistors be used?
> >
> > It's not whether the transistors are "new" or "old". The older
ones were
> > quite probably made with germanium metal, and the "junction drop"
in that
> > is about 0.2 Volt. Newer transistors are generally silicon, and the
> > junction drop in that is about 0.6 volts. This difference CAN make a
> > difference in audio circuits, etc.
>
> Yeah, where the actual linear operation of the part is concerned.
But this
> divider circuit he's talking about doesn't sound like that at all,
and I
> don't think it's gonna be a problem there.
>
> > For irrelevant reasons, I'd NEVER work on an electronic "organ"
unless it
> > were a matter of [my!] life or death! But if I were forced at
gun-point,
> > I'd ponder using a modern CMOS IC as a flip-flop.
>
> Not me!
>
> > WOULD require knowing some "working voltages" of many points, before
> > beginning, of course. GOOD LUCK! Jan Rowland
>
> I think this is the one he was talking about earlier on where only
six volts
> was present, though it isn't clear to me whether this is the actual
measured
> collector voltage or the power supply voltage.
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