Greetings, gentlemen,

I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
at a yard sale. Being 50 years old, however, it has a few faults and
needs realignment and whatnot. Before I can proceed with that, I've
discovered that the transistors it uses (mostly obsolete germanium
devices) suffer from tin whiskers so I will need to re-jig the board so
they can be replaced with silicon ones instead. The design is very
simple so it *shouldn't* be a big deal. The bias requirements are of
course different between germaniums and silicons so perhaps it would be
better to start from scratch? I want to remain faithful to the original,
simple design ethos with its five discrete transistors whatever I do.
Any suggestions?

Here's the schematic:

https://disk.yandex.com/i/a2xX6_IadjbgIw

CD.

On a sunny day (Sun, 19 Dec 2021 12:40:16 +0000) it happened Cursitor Doom
<cd@notformail.com> wrote in <spn97h$rou$1@dont-email.me>:

>Greetings, gentlemen,
>
>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>at a yard sale. Being 50 years old, however, it has a few faults and
>needs realignment and whatnot. Before I can proceed with that, I've
>discovered that the transistors it uses (mostly obsolete germanium
>devices) suffer from tin whiskers so I will need to re-jig the board so
>they can be replaced with silicon ones instead. The design is very
>simple so it *shouldn't* be a big deal. The bias requirements are of
>course different between germaniums and silicons so perhaps it would be
>better to start from scratch? I want to remain faithful to the original,
>simple design ethos with its five discrete transistors whatever I do.
>Any suggestions?
>
>Here's the schematic:
>
>https://disk.yandex.com/i/a2xX6_IadjbgIw

That is a classical audio amp.
Apart from I have never had a transistor fail due to 'tin whiskers',
if you replace ALL of those transistors with Si
then T2 R7/R8 will also change the bias to the output stage to 2 x Vbe, then 2 x .7V.
It should simply work.
But maybe you should increase R3 by 2 or more times or so to get enough bias for T3.

Or simply replace it with a LM380 or LM386!

Better even: Buy a nice Tecsun PL600 all band radio,
but... I bought one in 2014 for 60$, now I see them for 266$ on ebay!

Or the TECSUN PL660, perhaps, about 100$ on ebay.
Seems the PL600 is no longer made, and the 660 is the new model.

Do not hang on too much to old stuff.
(that said I hang on to my old analog scope).

On Sun, 19 Dec 2021 13:05:36 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

>On a sunny day (Sun, 19 Dec 2021 12:40:16 +0000) it happened Cursitor Doom
><cd@notformail.com> wrote in <spn97h$rou$1@dont-email.me>:
>
>>Greetings, gentlemen,
>>
>>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>at a yard sale. Being 50 years old, however, it has a few faults and
>>needs realignment and whatnot. Before I can proceed with that, I've
>>discovered that the transistors it uses (mostly obsolete germanium
>>devices) suffer from tin whiskers so I will need to re-jig the board so
>>they can be replaced with silicon ones instead. The design is very
>>simple so it *shouldn't* be a big deal. The bias requirements are of
>>course different between germaniums and silicons so perhaps it would be
>>better to start from scratch? I want to remain faithful to the original,
>>simple design ethos with its five discrete transistors whatever I do.
>>Any suggestions?
>>
>>Here's the schematic:
>>
>>https://disk.yandex.com/i/a2xX6_IadjbgIw
>
>That is a classical audio amp.
>Apart from I have never had a transistor fail due to 'tin whiskers',

Really? The AF117 type in particular (ubiquitous in British broadcast
recievers of the late 1960s) was *notorious* for shorting internally
due to whiskers.

>if you replace ALL of those transistors with Si
>then T2 R7/R8 will also change the bias to the output stage to 2 x Vbe, then 2 x .7V.
>It should simply work.
>But maybe you should increase R3 by 2 or more times or so to get enough bias for T3.
>
>Or simply replace it with a LM380 or LM386!

No! No! NO!! No ICs thanks very much! I may even try potting the new
silicon replacements into hollowed- out casings of the Ge devices to
keep it original looking.

>
>Better even: Buy a nice Tecsun PL600 all band radio,
>but... I bought one in 2014 for 60$, now I see them for 266$ on ebay!
>
>Or the TECSUN PL660, perhaps, about 100$ on ebay.
>Seems the PL600 is no longer made, and the 660 is the new model.
>
>Do not hang on too much to old stuff.

I specialise in old obsolete stuff. I prefer it!

>(that said I hang on to my old analog scope).

I have about 13 of 'em.

On a sunny day (Sun, 19 Dec 2021 13:21:46 +0000) it happened Cursitor Doom
<cd@notformail.com> wrote in <63curgddjaitboe4872itb788d5i9n1fdg@4ax.com>:

>On Sun, 19 Dec 2021 13:05:36 GMT, Jan Panteltje
><pNaOnStPeAlMtje@yahoo.com> wrote:
>
>>On a sunny day (Sun, 19 Dec 2021 12:40:16 +0000) it happened Cursitor Doom
>><cd@notformail.com> wrote in <spn97h$rou$1@dont-email.me>:
>>
>>>Greetings, gentlemen,
>>>
>>>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>>at a yard sale. Being 50 years old, however, it has a few faults and
>>>needs realignment and whatnot. Before I can proceed with that, I've
>>>discovered that the transistors it uses (mostly obsolete germanium
>>>devices) suffer from tin whiskers so I will need to re-jig the board so
>>>they can be replaced with silicon ones instead. The design is very
>>>simple so it *shouldn't* be a big deal. The bias requirements are of
>>>course different between germaniums and silicons so perhaps it would be
>>>better to start from scratch? I want to remain faithful to the original,
>>>simple design ethos with its five discrete transistors whatever I do.
>>>Any suggestions?
>>>
>>>Here's the schematic:
>>>
>>>https://disk.yandex.com/i/a2xX6_IadjbgIw
>>
>>That is a classical audio amp.
>>Apart from I have never had a transistor fail due to 'tin whiskers',
>
>Really? The AF117 type in particular (ubiquitous in British broadcast
>recievers of the late 1960s) was *notorious* for shorting internally
>due to whiskers.
>
>>if you replace ALL of those transistors with Si
>>then T2 R7/R8 will also change the bias to the output stage to 2 x Vbe, then 2 x .7V.
>>It should simply work.
>>But maybe you should increase R3 by 2 or more times or so to get enough bias for T3.
>>
>>Or simply replace it with a LM380 or LM386!
>
>No! No! NO!! No ICs thanks very much! I may even try potting the new
>silicon replacements into hollowed- out casings of the Ge devices to
>keep it original looking.
>
>>
>>Better even: Buy a nice Tecsun PL600 all band radio,
>>but... I bought one in 2014 for 60$, now I see them for 266$ on ebay!
>>
>>Or the TECSUN PL660, perhaps, about 100$ on ebay.
>>Seems the PL600 is no longer made, and the 660 is the new model.
>>
>>Do not hang on too much to old stuff.
>
>I specialise in old obsolete stuff. I prefer it!
>
>>(that said I hang on to my old analog scope).
>
>I have about 13 of 'em.

I was so happy when I bought my first PLL radio,
just type in the frequency!

I have always used scopes for fault finding, even worked at Tek.
build my own ones at home.
But as collectors item? No way!
Things are moving so fast, a good Rigol will get you value for money.
And I do not have space for all those boat anchors anyways,

On Sun, 19 Dec 2021 12:40:16 +0000, Cursitor Doom <cd@notformail.com>
wrote:

>Greetings, gentlemen,
>
>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>at a yard sale. Being 50 years old, however, it has a few faults and
>needs realignment and whatnot. Before I can proceed with that, I've
>discovered that the transistors it uses (mostly obsolete germanium
>devices) suffer from tin whiskers so I will need to re-jig the board so
>they can be replaced with silicon ones instead. The design is very
>simple so it *shouldn't* be a big deal. The bias requirements are of
>course different between germaniums and silicons so perhaps it would be
>better to start from scratch? I want to remain faithful to the original,
>simple design ethos with its five discrete transistors whatever I do.
>Any suggestions?
>
>Here's the schematic:
>
>https://disk.yandex.com/i/a2xX6_IadjbgIw
>
>CD.

Why are some people so adverse to drawing a simple straight 4-wire
connection? It's not as if dots slide off the page or anything.

--

I yam what I yam - Popeye

On Sun, 19 Dec 2021 15:07:33 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

>On a sunny day (Sun, 19 Dec 2021 13:21:46 +0000) it happened Cursitor Doom
><cd@notformail.com> wrote in <63curgddjaitboe4872itb788d5i9n1fdg@4ax.com>:
>
>>On Sun, 19 Dec 2021 13:05:36 GMT, Jan Panteltje
>><pNaOnStPeAlMtje@yahoo.com> wrote:
>>
>>>On a sunny day (Sun, 19 Dec 2021 12:40:16 +0000) it happened Cursitor Doom
>>><cd@notformail.com> wrote in <spn97h$rou$1@dont-email.me>:
>>>
>>>>Greetings, gentlemen,
>>>>
>>>>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>>>at a yard sale. Being 50 years old, however, it has a few faults and
>>>>needs realignment and whatnot. Before I can proceed with that, I've
>>>>discovered that the transistors it uses (mostly obsolete germanium
>>>>devices) suffer from tin whiskers so I will need to re-jig the board so
>>>>they can be replaced with silicon ones instead. The design is very
>>>>simple so it *shouldn't* be a big deal. The bias requirements are of
>>>>course different between germaniums and silicons so perhaps it would be
>>>>better to start from scratch? I want to remain faithful to the original,
>>>>simple design ethos with its five discrete transistors whatever I do.
>>>>Any suggestions?
>>>>
>>>>Here's the schematic:
>>>>
>>>>https://disk.yandex.com/i/a2xX6_IadjbgIw
>>>
>>>That is a classical audio amp.
>>>Apart from I have never had a transistor fail due to 'tin whiskers',
>>
>>Really? The AF117 type in particular (ubiquitous in British broadcast
>>recievers of the late 1960s) was *notorious* for shorting internally
>>due to whiskers.
>>
>>>if you replace ALL of those transistors with Si
>>>then T2 R7/R8 will also change the bias to the output stage to 2 x Vbe, then 2 x .7V.
>>>It should simply work.
>>>But maybe you should increase R3 by 2 or more times or so to get enough bias for T3.
>>>
>>>Or simply replace it with a LM380 or LM386!
>>
>>No! No! NO!! No ICs thanks very much! I may even try potting the new
>>silicon replacements into hollowed- out casings of the Ge devices to
>>keep it original looking.
>>
>>>
>>>Better even: Buy a nice Tecsun PL600 all band radio,
>>>but... I bought one in 2014 for 60$, now I see them for 266$ on ebay!
>>>
>>>Or the TECSUN PL660, perhaps, about 100$ on ebay.
>>>Seems the PL600 is no longer made, and the 660 is the new model.
>>>
>>>Do not hang on too much to old stuff.
>>
>>I specialise in old obsolete stuff. I prefer it!
>>
>>>(that said I hang on to my old analog scope).
>>
>>I have about 13 of 'em.
>
>I was so happy when I bought my first PLL radio,
>just type in the frequency!

Stability-wise they are of course far superior. However, if you want
to have a good, thorough snoop around the bands for what's on, then
analogue tuning still rules IMO. No serious SWL should be without a
tuning knob!

>I have always used scopes for fault finding, even worked at Tek.
>build my own ones at home.
>But as collectors item? No way!
>Things are moving so fast, a good Rigol will get you value for money.
>And I do not have space for all those boat anchors anyways,

Then make it!

On Sun, 19 Dec 2021 08:17:12 -0800, jlarkin@highlandsniptechnology.com
wrote:

>On Sun, 19 Dec 2021 12:40:16 +0000, Cursitor Doom <cd@notformail.com>
>wrote:
>
>>Greetings, gentlemen,
>>
>>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>at a yard sale. Being 50 years old, however, it has a few faults and
>>needs realignment and whatnot. Before I can proceed with that, I've
>>discovered that the transistors it uses (mostly obsolete germanium
>>devices) suffer from tin whiskers so I will need to re-jig the board so
>>they can be replaced with silicon ones instead. The design is very
>>simple so it *shouldn't* be a big deal. The bias requirements are of
>>course different between germaniums and silicons so perhaps it would be
>>better to start from scratch? I want to remain faithful to the original,
>>simple design ethos with its five discrete transistors whatever I do.
>>Any suggestions?
>>
>>Here's the schematic:
>>
>>https://disk.yandex.com/i/a2xX6_IadjbgIw
>>
>>CD.
>
>Why are some people so adverse to drawing a simple straight 4-wire
>connection? It's not as if dots slide off the page or anything.

I know! Stupid things like that really hinder my understanding of a
circuit's function as I'm focusing on that rather than anything else.

So anyways. Are you going to redesign this damn thing for me or what?
;-)

On Sun, 19 Dec 2021 17:32:52 +0000, Cursitor Doom <cd@notformail.com>
wrote:

>On Sun, 19 Dec 2021 08:17:12 -0800, jlarkin@highlandsniptechnology.com
>wrote:
>
>>On Sun, 19 Dec 2021 12:40:16 +0000, Cursitor Doom <cd@notformail.com>
>>wrote:
>>
>>>Greetings, gentlemen,
>>>
>>>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>>at a yard sale. Being 50 years old, however, it has a few faults and
>>>needs realignment and whatnot. Before I can proceed with that, I've
>>>discovered that the transistors it uses (mostly obsolete germanium
>>>devices) suffer from tin whiskers so I will need to re-jig the board so
>>>they can be replaced with silicon ones instead. The design is very
>>>simple so it *shouldn't* be a big deal. The bias requirements are of
>>>course different between germaniums and silicons so perhaps it would be
>>>better to start from scratch? I want to remain faithful to the original,
>>>simple design ethos with its five discrete transistors whatever I do.
>>>Any suggestions?
>>>
>>>Here's the schematic:
>>>
>>>https://disk.yandex.com/i/a2xX6_IadjbgIw
>>>
>>>CD.
>>
>>Why are some people so adverse to drawing a simple straight 4-wire
>>connection? It's not as if dots slide off the page or anything.
>
>I know! Stupid things like that really hinder my understanding of a
>circuit's function as I'm focusing on that rather than anything else.
>
>So anyways. Are you going to redesign this damn thing for me or what?
>;-)

I dislike audio. Why not buy some germanium transistors from Ebay?

Or a decent modern amp?

--

I yam what I yam - Popeye

On Sun, 19 Dec 2021 09:44:17 -0800, jlarkin@highlandsniptechnology.com
wrote:

>I dislike audio. Why not buy some germanium transistors from Ebay?

No point. The only parts available are NOS which will have whiskers
growing in them anyway, so they'll fail eventually guaranteed.

>Or a decent modern amp?

Naw. Gotta be discretes to keep it original. Fortunately, this is a
hybrid radio which uses both Si and Ge trannies, so I can get away
with replacing the Ge with Si devices whilst remainiing faithful to
the original concept. Of course I could stick an audio IC in there,
but it would be a cop-out and the kind of solution only a cad, a
bounder or possibly even a blackguard would consider.
So get your slide rule out. :-)

In article <hisurgda6flk6vrr51fiehes54s0cpe6g8@4ax.com>,
cd@notformail.com says...
>
> Naw. Gotta be discretes to keep it original. Fortunately, this is a
> hybrid radio which uses both Si and Ge trannies, so I can get away
> with replacing the Ge with Si devices whilst remainiing faithful to
> the original concept. Of course I could stick an audio IC in there,
> but it would be a cop-out and the kind of solution only a cad, a
> bounder or possibly even a blackguard would consider.
> So get your slide rule out. :-)
>
>
>

Have you tried this place, they list germanium transistors but at a
steep for some of them.

https://ntepartsdirect.com/

On Sun, 19 Dec 2021 18:03:13 +0000, Cursitor Doom <cd@notformail.com>
wrote:

>On Sun, 19 Dec 2021 09:44:17 -0800, jlarkin@highlandsniptechnology.com
>wrote:
>
>>I dislike audio. Why not buy some germanium transistors from Ebay?
>
>No point. The only parts available are NOS which will have whiskers
>growing in them anyway, so they'll fail eventually guaranteed.
>
>>Or a decent modern amp?
>
>Naw. Gotta be discretes to keep it original. Fortunately, this is a
>hybrid radio which uses both Si and Ge trannies, so I can get away
>with replacing the Ge with Si devices whilst remainiing faithful to
>the original concept. Of course I could stick an audio IC in there,
>but it would be a cop-out and the kind of solution only a cad, a
>bounder or possibly even a blackguard would consider.
>So get your slide rule out. :-)

You'll need to replace the horrible germanium biasing with horrible
silicon biasing.

20% distortion? 20% ain't bad.

--

I yam what I yam - Popeye

On a sunny day (Sun, 19 Dec 2021 17:30:55 +0000) it happened Cursitor Doom
<cd@notformail.com> wrote in <lsqurghujn6etdecbprdvvrq5j0gi356df@4ax.com>:

>On Sun, 19 Dec 2021 15:07:33 GMT, Jan Panteltje
><pNaOnStPeAlMtje@yahoo.com> wrote:
>
>>On a sunny day (Sun, 19 Dec 2021 13:21:46 +0000) it happened Cursitor Doom
>><cd@notformail.com> wrote in <63curgddjaitboe4872itb788d5i9n1fdg@4ax.com>:
>>
>>>On Sun, 19 Dec 2021 13:05:36 GMT, Jan Panteltje
>>><pNaOnStPeAlMtje@yahoo.com> wrote:
>>>
>>>>On a sunny day (Sun, 19 Dec 2021 12:40:16 +0000) it happened Cursitor Doom
>>>><cd@notformail.com> wrote in <spn97h$rou$1@dont-email.me>:
>>>>
>>>>>Greetings, gentlemen,
>>>>>
>>>>>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>>>>at a yard sale. Being 50 years old, however, it has a few faults and
>>>>>needs realignment and whatnot. Before I can proceed with that, I've
>>>>>discovered that the transistors it uses (mostly obsolete germanium
>>>>>devices) suffer from tin whiskers so I will need to re-jig the board so
>>>>>they can be replaced with silicon ones instead. The design is very
>>>>>simple so it *shouldn't* be a big deal. The bias requirements are of
>>>>>course different between germaniums and silicons so perhaps it would be
>>>>>better to start from scratch? I want to remain faithful to the original,
>>>>>simple design ethos with its five discrete transistors whatever I do.
>>>>>Any suggestions?
>>>>>
>>>>>Here's the schematic:
>>>>>
>>>>>https://disk.yandex.com/i/a2xX6_IadjbgIw
>>>>
>>>>That is a classical audio amp.
>>>>Apart from I have never had a transistor fail due to 'tin whiskers',
>>>
>>>Really? The AF117 type in particular (ubiquitous in British broadcast
>>>recievers of the late 1960s) was *notorious* for shorting internally
>>>due to whiskers.
>>>
>>>>if you replace ALL of those transistors with Si
>>>>then T2 R7/R8 will also change the bias to the output stage to 2 x Vbe, then 2 x .7V.
>>>>It should simply work.
>>>>But maybe you should increase R3 by 2 or more times or so to get enough bias for T3.
>>>>
>>>>Or simply replace it with a LM380 or LM386!
>>>
>>>No! No! NO!! No ICs thanks very much! I may even try potting the new
>>>silicon replacements into hollowed- out casings of the Ge devices to
>>>keep it original looking.
>>>
>>>>
>>>>Better even: Buy a nice Tecsun PL600 all band radio,
>>>>but... I bought one in 2014 for 60$, now I see them for 266$ on ebay!
>>>>
>>>>Or the TECSUN PL660, perhaps, about 100$ on ebay.
>>>>Seems the PL600 is no longer made, and the 660 is the new model.
>>>>
>>>>Do not hang on too much to old stuff.
>>>
>>>I specialise in old obsolete stuff. I prefer it!
>>>
>>>>(that said I hang on to my old analog scope).
>>>
>>>I have about 13 of 'em.
>>
>>I was so happy when I bought my first PLL radio,
>>just type in the frequency!
>
>Stability-wise they are of course far superior. However, if you want
>to have a good, thorough snoop around the bands for what's on, then
>analogue tuning still rules IMO. No serious SWL should be without a
>tuning knob!

Of course, my Tecsun radio has SSB, PLL, a BFO knob and a tuning knob.
Very good allband radio.
But my rtl-sdr stick with the xpsa spectrum analyzer software I wrote can use the mouse wheel for tuning to 1 Hz accuracy.
Just specify jump size 1:
http://panteltje.com/pub/xpsa-0.7.gif

>>I have always used scopes for fault finding, even worked at Tek.
>>build my own ones at home.
>>But as collectors item? No way!
>>Things are moving so fast, a good Rigol will get you value for money.
>>And I do not have space for all those boat anchors anyways,
>
>Then make it!
>
>

On Monday, December 20, 2021 at 3:17:22 AM UTC+11, jla...@highlandsniptechnology.com wrote:
> On Sun, 19 Dec 2021 12:40:16 +0000, Cursitor Doom <c...@notformail.com>
> wrote:
> >Greetings, gentlemen,
> >
> >I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
> >at a yard sale. Being 50 years old, however, it has a few faults and
> >needs realignment and whatnot. Before I can proceed with that, I've
> >discovered that the transistors it uses (mostly obsolete germanium
> >devices) suffer from tin whiskers so I will need to re-jig the board so
> >they can be replaced with silicon ones instead. The design is very
> >simple so it *shouldn't* be a big deal. The bias requirements are of
> >course different between germaniums and silicons so perhaps it would be
> >better to start from scratch? I want to remain faithful to the original,
> >simple design ethos with its five discrete transistors whatever I do.
> >Any suggestions?
> >
> >Here's the schematic:
> >
> >https://disk.yandex.com/i/a2xX6_IadjbgIw
> >
> >CD.
> Why are some people so adverse to drawing a simple straight 4-wire
> connection? It's not as if dots slide off the page or anything.
>

** The schem looks like it is from the UK.
Think the 45 degree angle convention is exactly because dots can disappear when making copies.

Amusing what autistics like JL find annoying......

....... Phil

jla...@highlandsniptechnology.com wrote:
====================================
>
> You'll need to replace the horrible germanium biasing with horrible
> silicon biasing.
>
> 20% distortion? 20% ain't bad.
> --

** Audiophobic JL just loves to piss on anything that does not help bloat his pathological ego.

The THD of that tiny amp is 1% at most, ffs it's in a portable radio.

...... Phil

First transistor BC108, it is a silicon one.
On Sun, 19 Dec 2021 12:40:16 +0000, Cursitor Doom <cd@notformail.com>
wrote:

>Greetings, gentlemen,
>
>I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>at a yard sale. Being 50 years old, however, it has a few faults and
>needs realignment and whatnot. Before I can proceed with that, I've
>discovered that the transistors it uses (mostly obsolete germanium
>devices) suffer from tin whiskers so I will need to re-jig the board so
>they can be replaced with silicon ones instead. The design is very
>simple so it *shouldn't* be a big deal. The bias requirements are of
>course different between germaniums and silicons so perhaps it would be
>better to start from scratch? I want to remain faithful to the original,
>simple design ethos with its five discrete transistors whatever I do.
>Any suggestions?
>
>Here's the schematic:
>
>https://disk.yandex.com/i/a2xX6_IadjbgIw
>
>CD.

Cursitor Doom wrote:
> On Sun, 19 Dec 2021 13:05:36 GMT, Jan Panteltje
> <pNaOnStPeAlMtje@yahoo.com> wrote:
>
>> On a sunny day (Sun, 19 Dec 2021 12:40:16 +0000) it happened Cursitor Doom
>> <cd@notformail.com> wrote in <spn97h$rou$1@dont-email.me>:
>>
>>> Greetings, gentlemen,
>>>
>>> I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>> at a yard sale. Being 50 years old, however, it has a few faults and
>>> needs realignment and whatnot. Before I can proceed with that, I've
>>> discovered that the transistors it uses (mostly obsolete germanium
>>> devices) suffer from tin whiskers so I will need to re-jig the board so
>>> they can be replaced with silicon ones instead. The design is very
>>> simple so it *shouldn't* be a big deal. The bias requirements are of
>>> course different between germaniums and silicons so perhaps it would be
>>> better to start from scratch? I want to remain faithful to the original,
>>> simple design ethos with its five discrete transistors whatever I do.
>>> Any suggestions?
>>>
>>> Here's the schematic:
>>>
>>> https://disk.yandex.com/i/a2xX6_IadjbgIw
>>
>> That is a classical audio amp.
>> Apart from I have never had a transistor fail due to 'tin whiskers',
>
> Really? The AF117 type in particular (ubiquitous in British broadcast
> recievers of the late 1960s) was *notorious* for shorting internally
> due to whiskers.
>
>> if you replace ALL of those transistors with Si
>> then T2 R7/R8 will also change the bias to the output stage to 2 x Vbe, then 2 x .7V.
>> It should simply work.
>> But maybe you should increase R3 by 2 or more times or so to get enough bias for T3.
>>
>> Or simply replace it with a LM380 or LM386!
>
> No! No! NO!! No ICs thanks very much! I may even try potting the new
> silicon replacements into hollowed- out casings of the Ge devices to
> keep it original looking.
>
>>
>> Better even: Buy a nice Tecsun PL600 all band radio,
>> but... I bought one in 2014 for 60$, now I see them for 266$ on ebay!
>>
>> Or the TECSUN PL660, perhaps, about 100$ on ebay.
>> Seems the PL600 is no longer made, and the 660 is the new model.
>>
>> Do not hang on too much to old stuff.
>
> I specialise in old obsolete stuff. I prefer it!
>
>> (that said I hang on to my old analog scope).
>
> I have about 13 of 'em.
>

If it's really 1971 vintage, that should work fine, with perhaps a bit
of attention to the biasing.

Back in the really old days, germaniums were sometimes leaky enough that
their apparent DC betas _changed sign_.

When I interviewed at Tektronix Beaverton back in 1987, one of their
crusty old vertical amp wizards (might have been Thor Hallen) gave me a
circuit to analyze that made no sense to me whatever--not at DC, not at
AC--its biasing was impossible, and I said so.

Turned out to have been an astable that only worked when the DC beta was
negative, but didn't much care how negative--it was guaranteed to start
up regardless.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Sunday, December 19, 2021 at 10:03:19 AM UTC-8, Cursitor Doom wrote:
> On Sun, 19 Dec 2021 09:44:17 -0800, jla...@highlandsniptechnology.com
> wrote:
> >I dislike audio. Why not buy some germanium transistors from Ebay?
> No point. The only parts available are NOS which will have whiskers
> growing in them anyway, so they'll fail eventually guaranteed.

Germanium doesn't generally have tin-whisker problems (those are particular to
a case design, not the transistor inside); it has additional failure modes and
aging issues, but so does any technology.

Be aware, though, that Si replacements for Ge transistors does change all the bias
currents, I've seen items burned up because of a naiive replace-with-modern-Si strategy.

On Sun, 19 Dec 2021 15:55:57 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Cursitor Doom wrote:
>> On Sun, 19 Dec 2021 13:05:36 GMT, Jan Panteltje
>> <pNaOnStPeAlMtje@yahoo.com> wrote:
>>
>>> On a sunny day (Sun, 19 Dec 2021 12:40:16 +0000) it happened Cursitor Doom
>>> <cd@notformail.com> wrote in <spn97h$rou$1@dont-email.me>:
>>>
>>>> Greetings, gentlemen,
>>>>
>>>> I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>>>> at a yard sale. Being 50 years old, however, it has a few faults and
>>>> needs realignment and whatnot. Before I can proceed with that, I've
>>>> discovered that the transistors it uses (mostly obsolete germanium
>>>> devices) suffer from tin whiskers so I will need to re-jig the board so
>>>> they can be replaced with silicon ones instead. The design is very
>>>> simple so it *shouldn't* be a big deal. The bias requirements are of
>>>> course different between germaniums and silicons so perhaps it would be
>>>> better to start from scratch? I want to remain faithful to the original,
>>>> simple design ethos with its five discrete transistors whatever I do.
>>>> Any suggestions?
>>>>
>>>> Here's the schematic:
>>>>
>>>> https://disk.yandex.com/i/a2xX6_IadjbgIw
>>>
>>> That is a classical audio amp.
>>> Apart from I have never had a transistor fail due to 'tin whiskers',
>>
>> Really? The AF117 type in particular (ubiquitous in British broadcast
>> recievers of the late 1960s) was *notorious* for shorting internally
>> due to whiskers.
>>
>>> if you replace ALL of those transistors with Si
>>> then T2 R7/R8 will also change the bias to the output stage to 2 x Vbe, then 2 x .7V.
>>> It should simply work.
>>> But maybe you should increase R3 by 2 or more times or so to get enough bias for T3.
>>>
>>> Or simply replace it with a LM380 or LM386!
>>
>> No! No! NO!! No ICs thanks very much! I may even try potting the new
>> silicon replacements into hollowed- out casings of the Ge devices to
>> keep it original looking.
>>
>>>
>>> Better even: Buy a nice Tecsun PL600 all band radio,
>>> but... I bought one in 2014 for 60$, now I see them for 266$ on ebay!
>>>
>>> Or the TECSUN PL660, perhaps, about 100$ on ebay.
>>> Seems the PL600 is no longer made, and the 660 is the new model.
>>>
>>> Do not hang on too much to old stuff.
>>
>> I specialise in old obsolete stuff. I prefer it!
>>
>>> (that said I hang on to my old analog scope).
>>
>> I have about 13 of 'em.
>>
>
>If it's really 1971 vintage, that should work fine, with perhaps a bit
>of attention to the biasing.
>
>Back in the really old days, germaniums were sometimes leaky enough that
>their apparent DC betas _changed sign_.

Just cap couple into the base, no bias needed.

(Electret mikes did that with jfets. I did that in my alligator
detector.)

--

I yam what I yam - Popeye

On Sun, 19 Dec 2021 12:44:35 -0800 (PST), Phil Allison
<pallison49@gmail.com> wrote:

>On Monday, December 20, 2021 at 3:17:22 AM UTC+11, jla...@highlandsniptechnology.com wrote:
>> On Sun, 19 Dec 2021 12:40:16 +0000, Cursitor Doom <c...@notformail.com>
>> wrote:
>> >Greetings, gentlemen,
>> >
>> >I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
>> >at a yard sale. Being 50 years old, however, it has a few faults and
>> >needs realignment and whatnot. Before I can proceed with that, I've
>> >discovered that the transistors it uses (mostly obsolete germanium
>> >devices) suffer from tin whiskers so I will need to re-jig the board so
>> >they can be replaced with silicon ones instead. The design is very
>> >simple so it *shouldn't* be a big deal. The bias requirements are of
>> >course different between germaniums and silicons so perhaps it would be
>> >better to start from scratch? I want to remain faithful to the original,
>> >simple design ethos with its five discrete transistors whatever I do.
>> >Any suggestions?
>> >
>> >Here's the schematic:
>> >
>> >https://disk.yandex.com/i/a2xX6_IadjbgIw
>> >
>> >CD.
>> Why are some people so adverse to drawing a simple straight 4-wire
>> connection? It's not as if dots slide off the page or anything.
>>
>
>** The schem looks like it is from the UK.
> Think the 45 degree angle convention is exactly because dots can disappear when making copies.
>
> Amusing what autistics like JL find annoying......
>
>
>...... Phil

Cheap British dots do fall off the paper. We use macho USA dots.

--

I yam what I yam - Popeye

LM wrote:
========
> First transistor BC108, it is a silicon one.
>

** Dates the radio to the mid/late 60s.

Next step up was to use AD161/162 output devices.
Germanium compliments in TO37 paks.

...... Phil

On 19/12/2021 20:59, whit3rd wrote:
> On Sunday, December 19, 2021 at 10:03:19 AM UTC-8, Cursitor Doom wrote:
>> On Sun, 19 Dec 2021 09:44:17 -0800, jla...@highlandsniptechnology.com
>> wrote:
>>> I dislike audio. Why not buy some germanium transistors from Ebay?
>> No point. The only parts available are NOS which will have whiskers
>> growing in them anyway, so they'll fail eventually guaranteed.
>
> Germanium doesn't generally have tin-whisker problems (those are particular to
> a case design, not the transistor inside); it has additional failure modes and
> aging issues, but so does any technology

Indeed. It's the metal case that's the primary cause of the problem in
this device. IIRC I believe Ge transistors are also far more easily
damaged by soldering into place than Si. We used to use needle-nose
pliers on the leads close to the case as a heat sink to protect them.

> Be aware, though, that Si replacements for Ge transistors does change all the bias
> currents, I've seen items burned up because of a naiive replace-with-modern-Si strategy.

Yes, I'm well aware of that, hence the question about re-jigging the
design to allow for said difference.

In article <spodeo$emp$1@dont-email.me>, cd@notformail.com says...
>
> Indeed. It's the metal case that's the primary cause of the problem in
> this device. IIRC I believe Ge transistors are also far more easily
> damaged by soldering into place than Si. We used to use needle-nose
> pliers on the leads close to the case as a heat sink to protect them.
>
>

I remember all the heat precautions from years ago. A while back I
started the SMD soldering and using a heat gun. Really had me worried
that playing all that hot air on the devices, but sofar in the few I
have replaced they seem to survived. Most of the SMD are smaller than
the tip of the soldering iron.

On 19/12/2021 20:59, whit3rd wrote:

<snipped>

> Germanium doesn't generally have tin-whisker problems (those are particular to
> a case design, not the transistor inside); it has additional failure modes and
> aging issues, but so does any technology.

Yebbut, tin whiskers are the spawn of communism dressed up as
environmentalism, and Crusty Oldloon must rail against them.

--
Cheers
Clive

Cursitor Doom wrote:
=================
> Greetings, gentlemen,

** Surely you jest?

>I want to remain faithful to the original,
> simple design ethos with its five discrete transistors whatever I do.
> Any suggestions?
>
> Here's the schematic:
>
> https://disk.yandex.com/i/a2xX6_IadjbgIw
>

** Looks fairly easy:

1. The BC108 can stay
2. Change T2 to a BC178 or similar TO18
3. Change T3 to 2N2904 or similar TO5
3. Change R3 to 820 ohms.
4. Change T4 to TIP31
5. Change T5 to TIP32

Step 2 ( Vbe multiplier) solves the bias issue for the new, Si outputs.

....... Phil

On Sunday, December 19, 2021 at 11:40:23 PM UTC+11, Cursitor Doom wrote:
> Greetings, gentlemen,
>
> I have a vintage MW/LW/SW 12V battery-powered radio I picked up recently
> at a yard sale. Being 50 years old, however, it has a few faults and
> needs realignment and whatnot. Before I can proceed with that, I've
> discovered that the transistors it uses (mostly obsolete germanium
> devices) suffer from tin whiskers so I will need to re-jig the board so
> they can be replaced with silicon ones instead. The design is very
> simple so it *shouldn't* be a big deal. The bias requirements are of
> course different between germaniums and silicons so perhaps it would be
> better to start from scratch? I want to remain faithful to the original,
> simple design ethos with its five discrete transistors whatever I do.
> Any suggestions?
>
> Here's the schematic:
>
> https://disk.yandex.com/i/a2xX6_IadjbgIw

This is sci.electronics.design. It's about designing electronics, not a place where you ask for advice about trivially simple class A/B audio amplifiers which have been around since transistors were first invented.

https://en.wikipedia.org/wiki/Power_amplifier_classes

There are some interesting ways of biasing the amplifier to get an adequate minimum standing current to minimise cross-over distortion without cooking the output transistors, but none of them are antiquated enough to be of interest to Cursitor Doom, nor popular enough for me to find a wikipedia reference.

Douglas Self and other audio guru's have spelled it out

http://www.douglas-self.com/ampins/dipa/dipa.htm

You have to scroll through to part 6 - "the blameless amplifier" where figure 33 shows an example (wrapped around Tr13).

-- Bill Sloman, Sydney