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Old 07-18-2013, 11:42 AM
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Selenium rectifiers

Need to buy two selenium rectifiers for a Philco 50-701 TV one is a .200a and one is a .130a
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Old 07-18-2013, 11:05 PM
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Have you looked at using modern diodes? I've heard plenty of stories about seleniums failing and stinking up the joint. I do have a handful of NOS and used seleniums but would have to check for the ratings.
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Old 07-18-2013, 11:30 PM
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Old 07-19-2013, 06:55 AM
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What type of diode would I need? Size?
Quote:
Originally Posted by bgadow View Post
Have you looked at using modern diodes? I've heard plenty of stories about seleniums failing and stinking up the joint. I do have a handful of NOS and used seleniums but would have to check for the ratings.
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Last edited by oldtvsandtoy; 07-19-2013 at 01:39 PM.
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Old 07-19-2013, 03:45 PM
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I find that the 1N4007 works for nearly all cases like this. You will also need a resistor in series with the diode, maybe 47 Ohms 2 Watts. 1N4007 diodes cost a few pennies each so buy a bunch for future use.
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Old 07-19-2013, 09:52 PM
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will that work for the .200a and .130 a?
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I find that the 1N4007 works for nearly all cases like this. You will also need a resistor in series with the diode, maybe 47 Ohms 2 Watts. 1N4007 diodes cost a few pennies each so buy a bunch for future use.
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Old 07-19-2013, 10:34 PM
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Quote:
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will that work for the .200a and .130 a?
1N4007 diodes can handle a full amp, so they should be more than enough to replace either of those.
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Old 07-20-2013, 02:44 AM
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one 1n4007 for one selenium rectifier , one for the other , its pretty easy to do and more reliable since the nos ones would fail after a while anyway.

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Old 07-20-2013, 11:53 AM
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Do I need a resistor in series? Would both be the same size?
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one 1n4007 for one selenium rectifier , one for the other , its pretty easy to do and more reliable since the nos ones would fail after a while anyway.

mike
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Old 07-20-2013, 04:55 PM
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A resistor is needed. See my post above.
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Old 07-25-2013, 04:10 PM
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Also not a bad idea to put a .01uF 600V film cap in parallel with the diode to reduce the increased switching noise inherent in modern diodes. It is called a snubber cap when used in this application IIRC.
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Old 09-06-2013, 08:22 AM
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We sure could use a good tutorial on replacing these. I'm diving into a Halolight that is going to need them, and I've never done it before. Even a simple diagram would work
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Old 09-06-2013, 08:42 AM
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To begin with while you have a working selenium in place, measure the voltage drop across it, the current running through it, and the shape of the rectified signal. Use the current, and voltage drop to figure out what resistor to put there..... And the scope pic of the wave after it, when you put a cap across it, compare the new picture to the old one..... Call it engineering a solution.
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Old 09-06-2013, 10:05 AM
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In this case, this set probably hasn't seen a wall receptacle since the Nixon administration, if not before that.

I have to do a full recap on it, so let's assume for the moment that I can't do that
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Old 09-06-2013, 10:17 AM
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A couple things I do, if replacing selenium with silicon, I would leave a term strip setup for a B+ dropping (and fuse for that matter if it does not have one), then use a variac and start at about 90v see how the set behaves (this is assuming its working). if everything working check the B+ at the output of the rectifier to the sams check the current and get a ballpark figure for the dropping resistor using ohms laws, prob between 50 and 200 ohms. check your line voltage and fine tune the resistor to the correct B+
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