Old germanium replacements?

B

Bob Morein

Guest
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely available?
ie, 2SA234, 2SA235, etc?
 
These are still available, but maybe not easily in their original numbers.
There are manufactures such as NTE, and ECG who have substitute germanium
replacements.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
=========================================


"Bob Morein" <nowhere@nowhere.com> wrote in message
news:SuCcnZaUEMVjnuSiXTWJlg@comcast.com...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely available?
ie, 2SA234, 2SA235, etc?
 
"Bob Morein" <nowhere@nowhere.com> wrote in message news:<SuCcnZaUEMVjnuSiXTWJlg@comcast.com>...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely available?
ie, 2SA234, 2SA235, etc?
Click to expand...
The NTE160 is listed as a replacement. A couple bucks each. It's got
pretty impressive specs (ft = 700 MHz) for a Germanium.

Lots of these old radios used the self-biasing properties of the original
germaniums, sometimes you have to add some biasing parts when you put in
different transistors.

Tim.
 
"Bob Morein" <nowhere@nowhere.com> wrote in message news:<SuCcnZaUEMVjnuSiXTWJlg@comcast.com>...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely available?
ie, 2SA234, 2SA235, etc?
Click to expand...
Try the following web site:

http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search?OpenForm

Jacques
 
"Bob Morein" bravely wrote to "All" (30 Sep 03 00:18:04)
--- on the heady topic of "Old germanium replacements?"

BM> Reply-To: "Bob Morein" <nowhere@nowhere.com>
BM> From: "Bob Morein" <nowhere@nowhere.com>
BM> Subject: Old germanium replacements?
BM> Organization: nowhere.com
BM> Xref: aeinews sci.electronics.repair:7069

BM> I've got an old Zenith portable I'm thinking of restoring.
BM> Are the Japanese germaniums used in a set like this widely available?
BM> ie, 2SA234, 2SA235, etc?

For the most part an old TV like yours isn't likely to use very critical
parts other than the Tuner and IF sections, so general replacements will
work. Sometimes outright replacing with modern silicon types will be
okay too but a knowledge of the circuit is needed before attempting if
it is possible. Rumors have some old germanium transistors were unstable
as surface contaminants may have dispersed throughout the die over time.
These were sometimes packed with a type of thermal transfer grease.

However, before replacing semiconductors a thorough check of all the
electrolytic capacitors is required because these cause perhaps 90% of
all electronic circuit failures. In addition old equipment that has been
sitting unused for long periods of time will inevitable require
reforming its electrolytic capacitors. Otherwise the electros may behave
very much like dead shorts or simply open because they are totally dry.

Asimov
******

.... No electrons were harmed in the posting of this message.
 
"Asimov" <Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote in message
news:MSGID_1=3a167=2f133.0_3f798abb@fidonet.org...
"Bob Morein" bravely wrote to "All" (30 Sep 03 00:18:04)
--- on the heady topic of "Old germanium replacements?"

BM> Reply-To: "Bob Morein" <nowhere@nowhere.com>
BM> From: "Bob Morein" <nowhere@nowhere.com>
BM> Subject: Old germanium replacements?
BM> Organization: nowhere.com
BM> Xref: aeinews sci.electronics.repair:7069

BM> I've got an old Zenith portable I'm thinking of restoring.
BM> Are the Japanese germaniums used in a set like this widely available?
BM> ie, 2SA234, 2SA235, etc?

For the most part an old TV like yours isn't likely to use very critical
parts other than the Tuner and IF sections,

It's a radio, not a TV.

[snip]

However, before replacing semiconductors a thorough check of all the
electrolytic capacitors is required because these cause perhaps 90% of
all electronic circuit failures.

I put an ESR meter on the electrolytic in the AC power supply section, and
to my surprise, it is in fine shape.

[snip]

My guess at this point is the audio outputs, based upon low volume and lack
of hiss.
 
"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0309300607.716e0967@posting.google.com...
"Bob Morein" <nowhere@nowhere.com> wrote in message
news:<SuCcnZaUEMVjnuSiXTWJlg@comcast.com>...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely available?
ie, 2SA234, 2SA235, etc?

The NTE160 is listed as a replacement. A couple bucks each. It's got
pretty impressive specs (ft = 700 MHz) for a Germanium.
Click to expand...
In a replacement, a much higher Ft than the original is not good. It means
a circuit may oscillate when it originally didn't.
 
"Michael A. Covington" <look@www.covingtoninnovations.com.for.address> wrote in message news:<7_CcnX-WKqN_VeGiU-KYvg@speedfactory.net>...
"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0309300607.716e0967@posting.google.com...
"Bob Morein" <nowhere@nowhere.com> wrote in message
news:<SuCcnZaUEMVjnuSiXTWJlg@comcast.com>...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely available?
ie, 2SA234, 2SA235, etc?

The NTE160 is listed as a replacement. A couple bucks each. It's got
pretty impressive specs (ft = 700 MHz) for a Germanium.

In a replacement, a much higher Ft than the original is not good. It means
a circuit may oscillate when it originally didn't.
Click to expand...
It's not clear to me what the Ft of the original 2SA234 and 2SA235 were.
I know they were used in RF sections of FM radios and TV's, which means
that they probably had Ft>300MHz.

If you have access to any of the original 2SA datasheets (did Hitachi make
these?) or just the specs, I'd be interested in what the real numbers are.

Tim.
 
"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0310022230.6b1bd7c@posting.google.com...
"Michael A. Covington" <look@www.covingtoninnovations.com.for.address
wrote in message news:<7_CcnX-WKqN_VeGiU-KYvg@speedfactory.net>...
"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0309300607.716e0967@posting.google.com...
"Bob Morein" <nowhere@nowhere.com> wrote in message
news:<SuCcnZaUEMVjnuSiXTWJlg@comcast.com>...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely
available?
ie, 2SA234, 2SA235, etc?

The NTE160 is listed as a replacement. A couple bucks each. It's got
pretty impressive specs (ft = 700 MHz) for a Germanium.

In a replacement, a much higher Ft than the original is not good. It
means
a circuit may oscillate when it originally didn't.

It's not clear to me what the Ft of the original 2SA234 and 2SA235 were.
I know they were used in RF sections of FM radios and TV's, which means
that they probably had Ft>300MHz.

If you have access to any of the original 2SA datasheets (did Hitachi make
these?) or just the specs, I'd be interested in what the real numbers are.

Tim.
Click to expand...
The first ones I'd like to replace are the 2SA156's in the audio output,
which I would imagine have a very low Ft.
 
"Bob Morein" <nowhere@nowhere.com> wrote in message news:<EfudnclvhdBcs-CiU-KYvA@comcast.com>...
The first ones I'd like to replace are the 2SA156's in the audio output,
which I would imagine have a very low Ft.
Click to expand...
The replacement for that is listed as the NTE126, which actually is a RF/IF
Ge transistor good to 250MHz. It's about $5 a pop, too.

What sort of can is the 2SA156 in? It's possible that NTE126 is actually
an appropriate choice despite the title on the top of the NTE data sheet...

The current lineup of NTE Germanium transistors is at

http://www.nteinc.com/Web_pgs/Germanium.html

There are a number listed specifically as "audio power amp" but they generally
are in TO-3 or TO-66 packages. In most cases it's best to ignore the NTE/ECG
sub books and go by specs/package instead.

Tim.
 
"Bob Morein" bravely wrote to "All" (03 Oct 03 04:09:37)
--- on the heady topic of "Re: Old germanium replacements?"

BM> Reply-To: "Bob Morein" <nowhere@nowhere.com>
BM> From: "Bob Morein" <nowhere@nowhere.com>
BM> Subject: Re: Old germanium replacements?
BM> Organization: nowhere.com
BM> Xref: aeinews sci.electronics.repair:7304


BM> "Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
BM> news:bec993c8.0310022230.6b1bd7c@posting.google.com...
"Michael A. Covington" <look@www.covingtoninnovations.com.for.address
BM> wrote in message news:<7_CcnX-WKqN_VeGiU-KYvg@speedfactory.net>...
"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0309300607.716e0967@posting.google.com...
"Bob Morein" <nowhere@nowhere.com> wrote in message
news:<SuCcnZaUEMVjnuSiXTWJlg@comcast.com>...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely
BM> available?
ie, 2SA234, 2SA235, etc?

The NTE160 is listed as a replacement. A couple bucks each. It's got
pretty impressive specs (ft = 700 MHz) for a Germanium.

In a replacement, a much higher Ft than the original is not good. It
BM> means
a circuit may oscillate when it originally didn't.

It's not clear to me what the Ft of the original 2SA234 and 2SA235 were.
I know they were used in RF sections of FM radios and TV's, which means
that they probably had Ft>300MHz.

If you have access to any of the original 2SA datasheets (did Hitachi make
these?) or just the specs, I'd be interested in what the real numbers are.

Tim.
Click to expand...
BM> The first ones I'd like to replace are the 2SA156's in the audio
BM> output, which I would imagine have a very low Ft.


I wouldn't count on it, some old point contact RF Germaniums had
surprising performance. But one obviously doesn't need it for audio.

The specs for 2SA234 states an Fab of 120MHz and the 2SA235's is 135MHz.
Fab is the common base cutoff frequency: Ft = (1+sqrt(2)) Fab

So Ft is about 2.4 times Fab. In this case about 290MHz & 325Mhz
respectively. Yes, Hitachi made them.

BTW why would you like to replace the audio outputs, unless you have
taken quantitative stage gain measurements?

Asimov
******

.... I worked hard to attach the electrodes to it.
 
"Asimov" <Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote in message
news:MSGID_1=3a167=2f133.0_3f7d7fee@fidonet.org...
"Bob Morein" bravely wrote to "All" (03 Oct 03 04:09:37)
--- on the heady topic of "Re: Old germanium replacements?"

BM> Reply-To: "Bob Morein" <nowhere@nowhere.com
BM> From: "Bob Morein" <nowhere@nowhere.com
BM> Subject: Re: Old germanium replacements?
BM> Organization: nowhere.com
BM> Xref: aeinews sci.electronics.repair:7304


BM> "Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
BM> news:bec993c8.0310022230.6b1bd7c@posting.google.com...
"Michael A. Covington" <look@www.covingtoninnovations.com.for.address
BM> wrote in message news:<7_CcnX-WKqN_VeGiU-KYvg@speedfactory.net>...
"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0309300607.716e0967@posting.google.com...
"Bob Morein" <nowhere@nowhere.com> wrote in message
news:<SuCcnZaUEMVjnuSiXTWJlg@comcast.com>...
I've got an old Zenith portable I'm thinking of restoring.
Are the Japanese germaniums used in a set like this widely
BM> available?
ie, 2SA234, 2SA235, etc?

The NTE160 is listed as a replacement. A couple bucks each. It's
got
pretty impressive specs (ft = 700 MHz) for a Germanium.

In a replacement, a much higher Ft than the original is not good. It
BM> means
a circuit may oscillate when it originally didn't.

It's not clear to me what the Ft of the original 2SA234 and 2SA235
were.
I know they were used in RF sections of FM radios and TV's, which means
that they probably had Ft>300MHz.

If you have access to any of the original 2SA datasheets (did Hitachi
make
these?) or just the specs, I'd be interested in what the real numbers
are.

Tim.

BM> The first ones I'd like to replace are the 2SA156's in the audio
BM> output, which I would imagine have a very low Ft.


I wouldn't count on it, some old point contact RF Germaniums had
surprising performance. But one obviously doesn't need it for audio.

The specs for 2SA234 states an Fab of 120MHz and the 2SA235's is 135MHz.
Fab is the common base cutoff frequency: Ft = (1+sqrt(2)) Fab

So Ft is about 2.4 times Fab. In this case about 290MHz & 325Mhz
respectively. Yes, Hitachi made them.

BTW why would you like to replace the audio outputs, unless you have
taken quantitative stage gain measurements?

The assumption is that because they are the only transistors in the set that
Click to expand...
run hot -- surprisingly hot -- they would be the first to diffuse. In fact,
that may be why they run hot.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top