Q: Where to get 1970's Selenium Stud Diodes

Discussion in 'General Electronics Chat' started by diyer, Aug 21, 2010.

  1. diyer

    Thread Starter New Member

    Apr 30, 2010
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    I am not an electronics repairman or engineer, so please forgive any errors, dumb mistakes, etc. I have a repair project I would like to do.

    Anyone know where I can get at least two or more 1970's Selenium Stud Diode/Rectifiers for a Schauer Battery Charger? The info on the side of the diodes says: AR004 G1. I do not have a schematic to determine anything more detailed than this info. I tried and Internet search for the schematic, but nothing turned up. I can provide pics of the inside if I am allowed to post them and then can figure out how to, but you all probably seen this before.

    I telephoned Schauer Manufacturing Corp., but they are out of business. Some new company has purchased the Schauer name, and their rep told me that Schauer sold off everything and all the info is gone. The employees are gone, and the building was demolished. He has no idea where the parts went. He also said the real name was Japlar. But I can tell you this about the charger: The model is 0122-06 C6612. It is a 120 volt, 10 amp, manual charger, weighs about 10 lbs. There is no circuit board. There is a big heavy transformer (which I tested and it is good), an ammeter gage, a circuit breaker, a heat sink plate that had the two selenium stud rectifiers on it, and a 6/12 volt switch. That's all that I know from looking at it. A local electronics repairman told me that you cannot find these parts anymore. That got me even more depressed.

    Thank you, diyer
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. diyer

    Thread Starter New Member

    Apr 30, 2010
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    Here are the pics:
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    Even though these parts are no longer made, you "could" try auction sites.

    If there was more information on the diode itself you could likely use a 'modern' diode to replace it.

    After all, if it is rated the same or larger, I dont really see a problem.

    They are connected to a heat sink that appears to be isolated from ground, so you may be able to use a bridge rectifier.

    Are you sure the diodes are shot?
     
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I had to replace one of those once but it was a dual. The manufacturer had it in stock for about $8
     
  6. diyer

    Thread Starter New Member

    Apr 30, 2010
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    Yes, I wish I had more info on the diodes. I dont see how they could be any good. The charger smoked when I turned it on after correcting the polarity. The later when I knew something went wrong inside and took the case off I noticed a burnt spot on the edge of the front spade connector to the diode. You can see it in the pic if you look close. When I was checking to make sure everything was secure, they pulled right in half very easily. They originally looked like two hockey pucks on top of each other. The two studs you see sticking up also had that black plastic around it (not sure what the material is). It cracked and pulled apart too easily. So, what I'm saying is that the diodes had a top half and a bottom half, so there was a total of 4 black plastic rings around them. I knew nothing about what they were three days ago. I thought they were just some fancy connection and that I could just solder each half back together. My biggest concern was what kind of solder to use, then I found some similar threads to this one and realized they were diodes (confirmed by a local friend).
     
  7. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Unfortunately replacing it with a modern diode isn't always an option, sometimes the way it knows when to lower or stop charging is based upon the voltage drop across that diode.

    Plenty of huge stud mount rectifiers still available, you'd need at least 50 PIV, an appropriate current rating, plenty of heat sink and a huge surge current capability as when you fist hook up to a semi-dead battery they pull quite a bit.

    Try the manufacturer's route first, may end up being cheaper that way anyway.
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Oh geez. Yeah it looks like you opened up a can of worms.

    I have no knowledge of these, so Ill step back and let the old hands take a crack at it.
     
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I didn't get all the way through your posts, looks like you're stuck putting in a replacement but not to worry, if it's a manual charger it just needs power rectifiers of no particular voltage drop.

    12V, 10A manual charger. Can you determine if the cathode or the anode would be the preferable mounting end for the rectifiers?
     
  10. diyer

    Thread Starter New Member

    Apr 30, 2010
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    A part seller that has them said its Cathode. I called the Brookwood Group (the new owners of the Schauer trademark) about the diode for the charger. This time I got a more friendly person and someone with more technical knowledge. Although he did not have any specs for the diode, or copies of the original schematic, he did not think the diodes were Selenium. He also said the schematics would not have any specs for the diodes anyway. He gave me the name of a company that purchased all of Schauer's inventory. So, I called them. The parts guy said the diodes in my charger were not selenium. He said he did not have the heat sink plate with the diodes attached as a whole part, i.e., a rectifier, but that he had the diodes separately, which are called "button diodes," 200V 50A. He told me the install procedure and I will need to rivet the heat sink plate back in place. I need to know if you guys know for sure that those diodes were in fact selenium? I have been reading about other people who want to repair their chargers, and the first answer always seems to be the alternative of using a silicon diode as a replacement part for the original part.

    So, the main question seems to be, were "Silicon Diodes" even made in 1978? If not, then perhaps they were selenium diodes.
     
  11. n1ist

    Active Member

    Mar 8, 2009
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    In this case, it looks like a manual charger. The transformer is center tapped; the tap goes thru the meter and out to one of the clips. The winding ends go thru the diodes, the circuit breaker, and out to the other clip. I would get a bridge rectifier, say 50V/20A or so. Wire the two transformer leads to the AC terminals on the bridge. If the clip connected to the circuit breaker is the positive one, wire the bridge's positive output to the circuit breaker, otherwise wire the negative. There will be one unused terminal on the bridge (you are only using two of the four diodes in there); just ignore it. Drill a hole and mount the bridge to the bottom of the case, with a little thermal goop, for heat sinking, and you should be set.
    /mike
     
  12. sage.radachowsky

    Member

    May 11, 2010
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    You might try American Microsemiconductor... they specialize in obsolete parts. I got some Germanium transistors from them last year.
     
  13. marshallf3

    Well-Known Member

    Jul 26, 2010
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    American Micro thinks everything they sell is gold. I get e-mails from them about diodes and such which are still commercially available in volume for 1/10 the price.

    The reason that transformer is center tapped is likely due to being a dual voltage charger (6/12V) but since you'd probably only need the 12V part anymore the bridge rectifier is a good suggestion.
     
  14. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    Those are not selenium rectifiers. If you want to see what a selenium rectifier would look like, check here:

    http://en.wikipedia.org/wiki/Selenium_rectifier

    Yes, there were silicon rectifiers in 1978, and well before that.

    Have a look at this page:

    http://wiki.answers.com/Q/Can_you_replace_a_selenium_rectifier_with_a_silicon_rectifier

    Also, FYI, have a look at this:

    http://yarchive.net/electr/selenium_rectifiers.html

    The earlier versions of that charger probably used selenium rectifiers, but by the time they manufactured the one you have, they had switched to silicon.

    Just do what n1ist suggested and get a 35 amp bridge rectifier and only use half the diodes in the package.
     
  15. Scotch Don

    New Member

    Aug 26, 2010
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    Replacements for selenium diodes:

    I recently had a Heathkit SB-610 Oscilloscope grace my bench, and the owner provided the HV caps to be replaced. Being the psychoanalyst that I am (wondering why the equipment 'went bad'), I delved into why non-polarized caps would suddenly go bad. Upon further study, I discovered that the selenium diodes had gone bad (and not the original caps). Of course I replaced the caps that the customer provided and went searching for replacement diodes. What I discovered on the net that 1N4007 rectifier diodes were much preferred over any other replacement diodes (especially the original selenium ones). In this application, no drop down resistor was needed; however, in other applications, a drop down resistor would be required.

    My question is: Is there a more appropriate direct replacement diode than the 1N4007, or simply going with the cheap 1N4007 and spend some time researching what value of drop down resistor (of 2-5 W) to use?

    Personally, I enjoy the challenge of psychoanalyzing the circuit; however, time may be more important to the owner.
     
  16. marshallf3

    Well-Known Member

    Jul 26, 2010
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    There's rarely any reason to put a diode in series with a modern slicon rectifier when replacing a selenium stack.
     
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