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From: N Cook on 19 Nov 2007 09:57
In a valve Dansette Bermuda of early 60s
Been in a loft for years.
The mains wiring is perished and other wiring looks dodgy so testing some
things cold first.
Using 9V battery and 300 ohm dropper shows near enough 9V over the
rectifier, how high V do you have to go with a good one to check it ?
Are there safety grounds anyway for changing to a 1N4007 or so ?
Single element rectifier
Siemens lazy S logo
Made in Germany
2250c50
Kc 0.6e 11/16


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



From: Jeff Liebermann on 19 Nov 2007 12:45
"N Cook" <diverse8(a)gazeta.pl> hath wroth:

>In a valve Dansette Bermuda of early 60s
>Been in a loft for years.
>The mains wiring is perished and other wiring looks dodgy so testing some
>things cold first.
>Using 9V battery and 300 ohm dropper shows near enough 9V over the
>rectifier, how high V do you have to go with a good one to check it ?

Dunno.

>Are there safety grounds anyway for changing to a 1N4007 or so ?

Yes. The original selenium rectifier has a rather substantial forward
voltage drop. The design of the filters and the rest of the receiver
take this into consideration. When you replace it with a 1N4007, the
forward voltage drop will be MUCH less. Chances are good that you'll
apply too much voltage to the filter caps and receiver.

If you're going to simulate a selenium rectifier, you'll probably need
to add a series resistor to drop the voltage somewhat.

http://hhscott.com/cc/rectifiers.htm
http://wiki.answers.com/Q/Can_you_replace_a_selenium_rectifier_with_a_silicon_rectifier

Also, watch out for dead electrolytic filter capacitors. They will
need to be "reformed":
<http://www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm>

>Single element rectifier
>Siemens lazy S logo
>Made in Germany
>2250c50
>Kc 0.6e 11/16
--
Jeff Liebermann jeffl(a)cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
From: captainvideo462002 on 19 Nov 2007 13:05
On Nov 19, 12:45 pm, Jeff Liebermann <je...(a)cruzio.com> wrote:
> "N Cook" <diver...(a)gazeta.pl> hath wroth:
>
> >In a valve Dansette Bermuda of early 60s
> >Been in a loft for years.
> >The mains wiring is perished and other wiring looks dodgy so testing some
> >things cold first.
> >Using 9V battery and 300 ohm dropper shows near enough 9V over the
> >rectifier, how high V do you have to go with a good one to check it ?
>
> Dunno.
>
> >Are there safety grounds anyway for changing to a 1N4007 or so ?
>
> Yes. The original selenium rectifier has a rather substantial forward
> voltage drop. The design of the filters and the rest of the receiver
> take this into consideration. When you replace it with a 1N4007, the
> forward voltage drop will be MUCH less. Chances are good that you'll
> apply too much voltage to the filter caps and receiver.
>
> If you're going to simulate a selenium rectifier, you'll probably need
> to add a series resistor to drop the voltage somewhat.
>
> http://hhscott.com/cc/rectifiers.htmhttp://wiki.answers.com/Q/Can_you_replace_a_selenium_rectifier_with_a...
>
> Also, watch out for dead electrolytic filter capacitors. They will
> need to be "reformed":
> <http://www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm>
>
> >Single element rectifier
> >Siemens lazy S logo
> >Made in Germany
> >2250c50
> >Kc 0.6e 11/16
>
> --
> Jeff Liebermann je...(a)cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

I would look at the working voltage rating of the original
electrolytics and make sure that the voltage which you apply with the
new silicon diode does not exceed 85 percent of it. Use a variac to do
this. It will also reform the electrolytics at the same time. But a a
previous posted said if the selenium unit is ok then I wouldn't bother
to replace it. Lenny Stein Barlen Electronics.
From: jakdedert on 19 Nov 2007 13:25
N Cook wrote:
> In a valve Dansette Bermuda of early 60s
> Been in a loft for years.
> The mains wiring is perished and other wiring looks dodgy so testing some
> things cold first.
> Using 9V battery and 300 ohm dropper shows near enough 9V over the
> rectifier, how high V do you have to go with a good one to check it ?
> Are there safety grounds anyway for changing to a 1N4007 or so ?
> Single element rectifier
> Siemens lazy S logo
> Made in Germany
> 2250c50
> Kc 0.6e 11/16
>
>
> --
> Diverse Devices, Southampton, England
> electronic hints and repair briefs , schematics/manuals list on
> http://home.graffiti.net/diverse:graffiti.net/
>
>
>
Ask in rec.antiques.radio+phono...or just google the subject in that
forum. It's been discussed at length. The general outcome is that yes,
you should replace the selenium with silicon. It's prone to self
destruct, and if it does, it emits nasty--some say toxic--fumes. (IOW
the magic smoke contained therein can harm you.)

There is a greater voltage drop across selenium. A series resister
should be added to compensate, calculated according to average B+
voltage/current.

jak
From: N Cook on 19 Nov 2007 14:08
jakdedert <jakdedert(a)bellsouth.net> wrote in message
news:xwk0j.2529$F87.1696(a)bignews6.bellsouth.net...
> N Cook wrote:
> > In a valve Dansette Bermuda of early 60s
> > Been in a loft for years.
> > The mains wiring is perished and other wiring looks dodgy so testing
some
> > things cold first.
> > Using 9V battery and 300 ohm dropper shows near enough 9V over the
> > rectifier, how high V do you have to go with a good one to check it ?
> > Are there safety grounds anyway for changing to a 1N4007 or so ?
> > Single element rectifier
> > Siemens lazy S logo
> > Made in Germany
> > 2250c50
> > Kc 0.6e 11/16
> >
> >
> > --
> > Diverse Devices, Southampton, England
> > electronic hints and repair briefs , schematics/manuals list on
> > http://home.graffiti.net/diverse:graffiti.net/
> >
> >
> >
> Ask in rec.antiques.radio+phono...or just google the subject in that
> forum. It's been discussed at length. The general outcome is that yes,
> you should replace the selenium with silicon. It's prone to self
> destruct, and if it does, it emits nasty--some say toxic--fumes. (IOW
> the magic smoke contained therein can harm you.)
>
> There is a greater voltage drop across selenium. A series resister
> should be added to compensate, calculated according to average B+
> voltage/current.
>
> jak


The owner likes the smell contained within, on lifting the lid.
Taking it apart it is even stronger old radio smell.
Does the selenium rectifier add to the smell in any way ? so replacing it
would "lessen the experience" ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


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