Selenium rectifier testing ?

Discussion in 'Electronic Repair' started by N Cook, Nov 19, 2007.

  1. N Cook

    N Cook Guest

    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/
     
    N Cook, Nov 19, 2007
    #1
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  2. N Cook

    mike Guest

    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/
    >
    >
    >

    If you want to listen to the radio, there are lots better ways to do it.

    OLD radios have emotional and monetary value just because they're old.
    I never understood why people pay huge bux for something just because
    it's old..."Hey, look at me, I just paid big bux for a radio that
    sounds like crap!! But I got one of only 1000 in existence.
    Ain't I cool?"...but I digress...

    I suggest that both the emotional and monetary value of an old thing is
    a strong function of it's "stockness". Stated another way, the
    less stuff you change, the more value it has. Stated another way,
    "If it ain't broke, don't fix it."

    Put your effort into forming the caps before you plug it in.

    --
    Return address is VALID!
     
    mike, Nov 19, 2007
    #2
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  3. "N Cook" <> 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
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 http://802.11junk.com
    Skype: JeffLiebermann AE6KS 831-336-2558
     
    Jeff Liebermann, Nov 19, 2007
    #3
  4. N Cook

    Guest

    On Nov 19, 12:45 pm, Jeff Liebermann <> wrote:
    > "N Cook" <> 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.ht...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
    > 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.
     
    , Nov 19, 2007
    #4
  5. N Cook

    James Sweet Guest


    >>

    > If you want to listen to the radio, there are lots better ways to do it.
    >
    > OLD radios have emotional and monetary value just because they're old.
    > I never understood why people pay huge bux for something just because it's
    > old..."Hey, look at me, I just paid big bux for a radio that
    > sounds like crap!! But I got one of only 1000 in existence.
    > Ain't I cool?"...but I digress...



    Well you may not agree with it, but it's certainly a common human thing to
    do. People pay big bucks for things a lot less useful than an old radio, one
    needs only to walk past a jewelry store to observe this. Diamonds are good
    for cutting things, that's my view, but obviously a whole lot of people
    disagree with me.

    That said, there's just nothing quite like listening to an old radio,
    definitely an emotional component to it, my '37 Zenith console is the only
    radio I ever listen to.
     
    James Sweet, Nov 19, 2007
    #5
  6. N Cook

    jakdedert Guest

    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
     
    jakdedert, Nov 19, 2007
    #6
  7. N Cook

    mike Guest

    James Sweet wrote:
    >> If you want to listen to the radio, there are lots better ways to do it.
    >>
    >> OLD radios have emotional and monetary value just because they're old.
    >> I never understood why people pay huge bux for something just because it's
    >> old..."Hey, look at me, I just paid big bux for a radio that
    >> sounds like crap!! But I got one of only 1000 in existence.
    >> Ain't I cool?"...but I digress...

    >
    >
    > Well you may not agree with it, but it's certainly a common human thing to
    > do. People pay big bucks for things a lot less useful than an old radio, one
    > needs only to walk past a jewelry store to observe this. Diamonds are good
    > for cutting things, that's my view, but obviously a whole lot of people
    > disagree with me.
    >
    > That said, there's just nothing quite like listening to an old radio,
    > definitely an emotional component to it, my '37 Zenith console is the only
    > radio I ever listen to.
    >
    >

    Post a picture of the rig you use to take that zenith jogging.

    I agree, I just don't practice.

    I can think of only one old thing that I wish I still had...nope,
    I really don't want her back either... ;-)

    Out with the old, in with the fully depreciated...

    --
    Return address is VALID!
     
    mike, Nov 19, 2007
    #7
  8. N Cook

    N Cook Guest

    jakdedert <> wrote in message
    news:xwk0j.2529$...
    > 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/
     
    N Cook, Nov 19, 2007
    #8
  9. N Cook

    Ron(UK) Guest

    N Cook wrote:

    > Does the selenium rectifier add to the smell in any way ?


    They certainly do when they fail!

    Ron(UK)
     
    Ron(UK), Nov 19, 2007
    #9
  10. N Cook

    James Sweet Guest


    > Post a picture of the rig you use to take that zenith jogging.
    >
    > I agree, I just don't practice.
    >
    > I can think of only one old thing that I wish I still had...nope,
    > I really don't want her back either... ;-)
    >
    > Out with the old, in with the fully depreciated...
    >



    I take my iPod jogging, I listen to CDs in the car, the content on either is
    far superior, but it's not the same experience as sitting by the fire near
    the warm glow of a classic radio. It's not about the content or the sound
    quality.
     
    James Sweet, Nov 19, 2007
    #10
  11. N Cook

    Guest

    On Nov 19, 9:57 am, "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 onhttp://home.graffiti.net/diverse:graffiti.net/


    Mpffff... let's try to answer the question, at least a little bit.

    a) The OEM selenium diode is prone to failure. When it fails it does
    so in a spectacular manner such that you will offend any and all
    parties within smell-range and at the same time release fumes that are
    toxic (but by no means as toxic as they smell). So: Get rid of it.
    Better yet, leave it in place for appearance but hide the new silicon
    diode behind it.

    b) There is a significant voltage-drop across the diode. In battery
    sets (typically with 1.4V tubes, not accounting for this drop can
    either greatly shorten tube life *or* blow filaments altogether.

    c) As selenium diodes age, they increase in resistance. Many battery
    sets (with specific reference to the post-war, miniature-tube Zenith
    TransOceanic series) will fail due to too-low filament voltage from
    this cause. On the other hand, with some of their mains-only radios,
    with specific reference to the post-war AM/FM units, this is not a
    major issue.

    So: Yes, replace the diode. Add a resistor in series to get the proper
    filament voltage if this is a concern. For the T/O series, that can
    work out somewhere between 30 and 80 ohms @ 2 watts (use 5 if you can)
    or better. Such a resistor is harder to conceal than the diode, but it
    does make the radio functional with reasonable safety. But if the down-
    line components from the rectifier are not voltage-sensitive, you may
    not have to add the dropping resistor.

    Now, keep in mind that if you are replacing a single selenium diode
    (i.e.: NOT a stack), the forward voltage drop is insignificant such
    that no additional resistor is required. Or, you can put a zener diode
    across the filament string (if so equipped), to protect the tubes.

    Peter Wieck
    Wyncote, PA
     
    , Nov 19, 2007
    #11
  12. N Cook

    mike Guest

    James Sweet wrote:
    >> Post a picture of the rig you use to take that zenith jogging.
    >>
    >> I agree, I just don't practice.
    >>
    >> I can think of only one old thing that I wish I still had...nope,
    >> I really don't want her back either... ;-)
    >>
    >> Out with the old, in with the fully depreciated...
    >>

    >
    >
    > I take my iPod jogging, I listen to CDs in the car, the content on either is
    > far superior, but it's not the same experience as sitting by the fire near
    > the warm glow of a classic radio. It's not about the content or the sound
    > quality.
    >
    >

    I picked up a pair of Dynaco Monoblock amplifiers at a garage sale.
    Hooked 'em up and couldn't tell that they sounded any different.
    Definitely winter weather amplifiers. Coulda roasted wieners on 'em.
    Luckily, I found someone who thought they did sound better and offered
    me 10x what I paid for them. Out they went. I live in a no-nostalgia
    zone. ;-)

    --
    Return address is VALID!
     
    mike, Nov 20, 2007
    #12
  13. N Cook

    Tim Schwartz Guest

    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/
    >
    >
    >

    Nigel,

    Take another look at the number. Might it be "B250C50"? Many European
    rectifiers used to give you the voltage (B, in this case 250 volts) and
    current rating (C, in this case 50mA) of the device.

    I agree with the other posters that you can replace the selenium with a
    silicon diode, but may need to ad a dropping resistor as the B+ may be
    higher because of less loss in the rectifier. I usually bring the item
    up slowly on a variac and make sure that I don't exceed the voltage
    of the filter caps. Better still if you have a factory diagram telling
    you what the B+ is supposed to be. Then you can choose an appropriate
    resistor, and you might need quite a few watts worth too.

    Unfortunately, I can't suggest how you might test the selenium.

    Regards,
    Tim Schwartz
    Bristol Electronics
     
    Tim Schwartz, Nov 20, 2007
    #13
  14. N Cook

    N Cook Guest

    Tim Schwartz <> wrote in message
    news:...
    > 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/
    > >
    > >
    > >

    > Nigel,
    >
    > Take another look at the number. Might it be "B250C50"? Many European
    > rectifiers used to give you the voltage (B, in this case 250 volts) and
    > current rating (C, in this case 50mA) of the device.
    >
    > I agree with the other posters that you can replace the selenium with a
    > silicon diode, but may need to ad a dropping resistor as the B+ may be
    > higher because of less loss in the rectifier. I usually bring the item
    > up slowly on a variac and make sure that I don't exceed the voltage
    > of the filter caps. Better still if you have a factory diagram telling
    > you what the B+ is supposed to be. Then you can choose an appropriate
    > resistor, and you might need quite a few watts worth too.
    >
    > Unfortunately, I can't suggest how you might test the selenium.
    >
    > Regards,
    > Tim Schwartz
    > Bristol Electronics


    I have a1979 Siemens databook and E250C50 were still listed,
    rating only 200V, 20mA

    I removed and tried on a bench supply thru 330 ohms.
    Took to 25V and read over the rectifier 25V, powered either way

    So will replace with silicon

    --
    Diverse Devices, Southampton, England
    electronic hints and repair briefs , schematics/manuals list on
    http://home.graffiti.net/diverse:graffiti.net/
     
    N Cook, Nov 20, 2007
    #14
  15. N Cook

    James Sweet Guest


    >>

    > Nigel,
    >
    > Take another look at the number. Might it be "B250C50"? Many European
    > rectifiers used to give you the voltage (B, in this case 250 volts) and
    > current rating (C, in this case 50mA) of the device.
    >
    > I agree with the other posters that you can replace the selenium with a
    > silicon diode, but may need to ad a dropping resistor as the B+ may be
    > higher because of less loss in the rectifier. I usually bring the item up
    > slowly on a variac and make sure that I don't exceed the voltage
    > of the filter caps. Better still if you have a factory diagram telling you
    > what the B+ is supposed to be. Then you can choose an appropriate
    > resistor, and you might need quite a few watts worth too.
    >
    > Unfortunately, I can't suggest how you might test the selenium.
    >



    There isn't realy any reason to test them. Given how nasty it is when they
    fail, and how likely that is to occur, I replace them any time I encounter
    them.
     
    James Sweet, Nov 20, 2007
    #15
  16. Tim Schwartz schrieb:
    >
    > 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

    ....

    > Nigel,
    >
    > Take another look at the number. Might it be "B250C50"?


    "B" stands for _B_rücken-Gleichrichter (bridge rectifier), whereas
    "E" stands for _E_inweg-Gleichrichter (half-wave rectifier).

    250: rated voltage = 250 V
    "C" stands for _c_apacitive load.
    50: rated current with capative load = 50 mA

    HTH

    Reinhard
     
    Reinhard Zwirner, Nov 21, 2007
    #16
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